Margaret Murnane

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ORAL HISTORIES
Image of Margaret Murnane

Credit: Steven Burrows

Interviewed by
David Zierler
Interview date
Location
Video conference
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Interview of Margaret Murnane by David Zierler on August 6, 2020,
Niels Bohr Library & Archives, American Institute of Physics,
College Park, MD USA,
www.aip.org/history-programs/niels-bohr-library/oral-histories/47194

For multiple citations, "AIP" is the preferred abbreviation for the location.

Interview with Margaret Murnane, professor of physics at the University of Colorado, Boulder, fellow at JILA, and director of the NSF STROBE Science and Technology Center. Murnane recounts her childhood in Ireland and emphasizes that, culturally, she was encouraged to pursue her interests in science from a young age. She discusses her undergraduate education at University College Cork where she focused on physics and developed her specialties in experimentation with light. Murnane describes the opportunities leading to her graduate work at UC Berkeley, where, for her thesis research, she developed a high-power femtosecond laser to create X-ray emitting plasma. She describes her first faculty appointment at Washington State University in Pullman where she continued work in ultrafast laser science, and she explains the decision to transfer to the University of Michigan at the Center for Ultrafast Optics. Murnane discusses her subsequent decision to join the faculty at JILA, where the instrumentation and opportunities for collaboration in her field were peerless. She describes the centrality of achieving very fast X-ray pulses to her field, and she describes some recent advances in applications such as EUV lithography. Murnane discusses the work that remains to be done to ensure that STEM promotes diversity and inclusivity, and she reflects on the many excellent graduate students she has mentored. At the end of the interview, Murnane conveys her excitement at the possibilities offered in the future of ultrafast lasers, including the ability of real-time microscopes that can make three-dimensional nanoscale and A-scale movies.

Transcript

Zierler:

Okay, here we go. This is David Zierler, oral historian for the American Institute of Physics. It is August 6th, 2020. I am so happy to be here with Professor Margaret Murnane. Margaret, thank you so much for joining me today.

Murnane:

Thanks for the opportunity, David.

Zierler:

Okay. So, to start, will you please tell me your title and institutional affiliation?

Murnane:

So, I’m a professor at the University of Colorado in Boulder in the physics department. I’m also a fellow of JILA. And then also the director of the NSF STROBE Science and Technology Center.

Zierler:

Okay. Let’s take it all the way back to the beginning. Take us back to Ireland and I’d like to start first with learning a little bit about your parents and where they are from.

Murnane:

Yes, I was very fortunate to have really amazing parents. My mother is still alive thankfully, but neither my mother or father had the opportunity to attend college. As I was growing up, they were so good at conveying the opportunities that one could access from education, as well as the excitement in learning. They were both intellectually curious and adventuresome. When I was growing up in the early sixties in Ireland, very few people had an opportunity to go to college. Fortunately, the country invested in opening up slots in the universities. So, I was part of a first larger cohort that had the opportunity to attend college - around ten percent when I was in high school. But thankfully, much more nowadays. So, my parents most definitely were my inspiration. I grew up in the countryside, so my brother and I could be out exploring nature, using our imaginations, learning to be independent very early. My father was a grade schoolteacher, who taught forty six-year-olds for forty years. Each evening when my father came home, he would give me a math puzzle and if I solved it, he would give me Coca-Cola or a potato crisps or chocolates, which I loved. So, he was amazing. Because he had taught six-year-olds for many years, he knew exactly how the young brain worked. So, if you associate something positive with solving puzzles, then it’s something that kids will want to do for the rest of their lives. Help people to be happy doing something useful that they love.

Zierler:

What were your parents’ professions, Margaret?

Murnane:

So, for my mom who is an inspiration for me, there were almost no opportunities for women to work outside of the home as she entered adulthood. So, she raised her kids, and fortunately, she had opportunities to work later in life helped by government retraining programs. She worked on data gathering for the government for the census and other activities, and very much appreciated the opportunity to contribute to society. My dad was a grade schoolteacher, who gave me the basic skills to become a scientist – always questioning and analyzing the world.

Zierler:

And where did you grow up? What neighborhood did you grow up in?

Murnane:

So, I like to say I grew up in the middle of nowhere (laughter). Our closest neighbors were about a half mile away. I grew up in a spectacularly beautiful place. We lived in a rented house right by the Shannon, which is the longest river in Ireland. It was just amazingly beautiful. The long summer evenings and rainbows helped with my fascination with light. There were challenges, such as no running water, but our parents made our lives so rich that we did not really notice.

Zierler:

Margaret, I’m curious if you were encouraged as a girl that science was an avenue of interest and career opportunity that was possible for you to pursue?

Murnane:

Ah, that’s very interesting. So, my parents helped me to pursue a path that many women scientists took - I was fortunate to attend gender-segregated grade and high schools.

Zierler:

Mm-hmm.

Murnane:

My parents arranged for me to go to school in the local big town, Limerick. This was where my dad taught, so I could commute with him every day. It was a hard decision for my parents to make when I was in grade school because that meant a forty-five-minute trip each way. But the schools in the town had many more resources than local schools, at least at that pre-internet time period. And the high school I attended had the only physics lab for girls, I believe, in the whole county. I was fortunate to have amazing teachers in both grade school and high school. They were both inspirational and exceptionally effective teachers. No one mentioned that girls could not do science. In fact, I didn’t hear that statement until I came to the U.S. Because Ireland was transitioning so rapidly and amazingly as I was growing up, transforming from an agricultural economy to a high-tech economy by the mid-1990s. In that kind of transition, people are not limited by the pathways their parents took. Everybody was getting more opportunities. It is fascinating to see a country transform to provide a better future for everyone.

Zierler:

Now, your high school was a public school or a private school?

Murnane:

The grade school and high schools that I attended were public. The high school had public and private sections, and the public section that I attended was taught in the Irish language. So, provided that one could pass quite challenging entrance exams, one could access an amazing education. I was fortunate to be around many really bright and amazing young women, which built up our confidence. So, both in grade school and high school, I encountered many very excellent female teachers and role models. This aspect is related to the Irish culture, which supports strong women. We are so fortunate to have had Doctors Mary Robinson and Mary McAleese as former Presidents of Ireland. And in our legends, Ireland celebrates strong queens and kings as great leaders.

Zierler:

So, you put to your advantage going through an all girls’ curriculum? You thought that gave you certain opportunities that you might not have?

Murnane:

I didn’t know. I had no idea- I was the first person in my extended family to have the opportunity to attend college. So, clearly it was my parents who nurtured the love of learning, and I was fortunate to have teachers who pushed girls to excel. They knew I loved science and math, and like many first-generation students who attend university, several deliberate and fortunate meetings, and hard work, combined to give me an opportunity to study science. At present in Ireland, most parents would understand the full landscape of educational opportunities. Back in the sixties and early seventies, there was a huge gap. Most people did not travel that much, and we didn’t have a phone, for example. None of my immediate family and flown to another country, except for grand aunts and uncles who had immigrated to the U.S. So, there was a big gap in people understanding what opportunities were able. I didn’t learn about graduate school until I went to college. Of course, this not true anymore. My niece and nephew who live in the west of Ireland have been travelling to other countries since they were small babies, with their own passports. There are amazing kids everywhere, but if they don’t know about opportunities in STEM and they don’t feel welcome, then they won’t follow those paths.

Zierler:

When you were thinking about undergraduate programs, were you thinking specifically about physics already, or that came later on?

Murnane:

Yes, I loved physics. But physics was my worst subject. I could get “As” in almost everything except physics and-

Zierler:

Really?

Murnane:

-my physics teacher would keep saying, “…I’m very disappointed with the ‘B’” (laughter). So, when I told my biology teacher that I wanted to do physics, he suggested that, “You might want to look at other programs also” (laughter). But, because my experience was limited, I didn’t actually read that as negative. I just figured, “Okay, I should look at physics and math also.” And then, it was very funny. When I got to college, I met a wonderful lecturer for my physics class, and the first week in college, I told him that I wanted to be a physics professor. So, he advised, “Well, maybe you shouldn’t put all your eggs in one basket” (laughter). But, again, because I didn’t have any understanding of potential barriers, I did not worry too much. And he and other professors strongly encouraged me as I progressed. Most had done their PhD’s in the U.S. It was amazing. There were just a few people per class, so we got to know the professors. They treated us like we were part of the community. It was a tough program, but the thing that was wonderful is that there was the sense of community.

Zierler:

Now, University College Cork, of course, was men and women. It wasn’t an all-girls’ school.

Murnane:

No, UCC was co-ed. And it just so happened in my class there was just two women. We were the only two women for several years, but we were the first to go to college in both our families. In our extended families. Brid received a PhD from Caltech and I from Berkeley.

Zierler:

Did you find it was a difficult transition going to college as a coed environment?

Murnane:

No. It was wonderful to meet people from all over the world and help some of my classmates to understand physics.

Zierler:

You had the confidence, I guess? You could hold your own.

Murnane:

I had confidence and did not see barriers. And then we would hang out with the chemists where the subculture’s a little different.

Zierler:

How did you overcome difficulties-

Murnane:

The people in the program were amazing and we formed a cohort. One classmate a few of years ahead later became President of UCC. Another colleague became department chair. And we did a lot of the things together. And occasionally when we felt a little bit of condescension, it was mild enough that we would just laugh. Or figure it out another way. And, so, for the most part the professors were very, very good at projecting the same expectations for everyone.

Zierler:

How did you overcome the difficulties that you experienced in physics in high school to realize that you had a special talent in this area?

Murnane:

Oh, no. I never felt I had a special talent. I figured one just worked hard. And, but you know, undergrad physics is not about science discoveries. And I was pretty good at getting good grades even if I didn’t understand everything. My forte is not perfecting knowledge or being able to get the best grades. I like to figure out a path to get somewhere where you’re really in the dark just muddling along and working with others to find the answer. And it turns out that that’s a very good talent to have as a scientist if you’re exploring a new area. Because you can’t depend upon what other people already know. You really do have to try to get people together have them comfortable admitting none of us know what we’re doing. But we might have just taken some weird and unexpected data and we’ve got to try and figure it out. It turns out that that effort is equally social and scientific. So, that’s what I think Ireland does well. People like other people. And we don’t think we can do it alone. And it turns out that’s exactly what you need to do to solve a hard problem.

Zierler:

Interesting. Now, does UCC have a PhD program?

Murnane:

Yes. UCC grew from under 5,000 students when I attended to around 30,000 students. Not only does it have a PhD program, but it has some fabulous national institutes that bring together university research and industry. So, they have people working there from Intel and many other companies. So, it’s thriving. One of my colleagues Seamus Davis, left Cornell and went back to a joint position between Cork and Oxford.

Zierler:

Now, you only stayed for the master’s degree. Was the plan originally to stay on for the PhD as well?

Murnane:

No. There was no PhD at the time.

Zierler:

At the time. I see.

Murnane:

The reason I did a master’s is that, again, at the time there wasn’t a tradition of leaving Ireland and returning. If you actually left for the U.S. for the most part, that meant you were actually not going to go back to Ireland. And so, my parents, they supported going to college, since they didn’t have this opportunity. But they did not understand what a PhD was. They didn’t understand why anybody would want one. But now I am so happy that my mom has met Ireland’s leaders, including President Michael Higgins, Chancellor Mary Robinson, and Tainiste Leo Varadkar.

Zierler:

I’m curious, Margaret, how well formed your identity as a physicist was by the time you had completed your master’s degree? In other words, when you determined that you wanted to continue onto the PhD, how well completed was your idea about being a theorist, being an experimentalist, the kind of physics…?

Murnane:

Yes. I knew that I wanted to be an experimentalist and work with light. I loved optics. But I definitely did not have a super strong identity. I loved learning. But I didn’t have a career plan and the reason I wanted to be a professor is that I loved teaching. So, all during college I would help the premeds or other students try to pass physics. So, I was always teaching other people. My dad was such a fantastic teacher. So, combining the two things I loved, science and teaching, I figured, that’s a professor. As far as I knew (laughter)

But then, the interesting thing was that when I got to Berkeley, immediately- you know, there were very few women in the class, all the women in the class ahead of me and behind left the program. They passed all the exams, but they just didn’t feel welcome. And people would say to the five women in my class “You just need to find a job at a teaching college” or “you were admitted because you are a woman.” Of course, people didn’t understand what they were doing, that they were pushing women out. It was a different time. But when there is a monoculture, people do crazy things that if they were outside the environment they would realize, you wouldn’t want to do that to any student, you know? This is why I’ve worked with APS and many organizations to try to help ourselves as a discipline not scare away the people trying to pursue physics a career.

Zierler:

Now, Margaret, was there a specific thing that attracted you to Berkeley? In other words, how big was your purview in terms of, did you want to come to the states? Were you thinking that you wanted to move beyond Ireland for a PhD?

Murnane:

There were so few PhD slots within Ireland and funds were limited to a small stipend. So, if I didn’t go somewhere that paid a living-wage RA, there would be no way to do a PhD. The wonderful thing is that several of the people I was studying with at Cork, as well as our professors, gave us advice and help. They told us to study for the GRE and apply to several schools. I joke with my own students now that there was no broad internet at that time, so the graduate schools would snail mail a brochure. In the end, I chose Berkeley because another UCC student was there already (Stephen Fahy and his wife Emer), so there were people there to give advice.

Zierler:

Had you been to the United States before?

Murnane:

No. Dublin and Belfast were the farthest I’d travelled.

Zierler:

Oh wow. Berkeley must have felt so big to you.

Murnane:

Interestingly, for seven years I thought everywhere in the U.S. was like Berkeley (laughter).

Zierler:

That is a very, very skewed view of the United States (laughter).

Murnane:

It was so funny. There was a group of us who hung out together from Brazil and the UK and some Irish people and German people. We all had similar culture adjustments to make, for instance, we couldn’t understand why people would say, “Have a nice day.” Because they clearly didn’t mean it, but we didn’t understand that it was just something to say (laughter).

Zierler:

Now did you, Margaret, did you have an idea of who you wanted to work with at Berkeley or you developed an adviser relationship when you got there?

Murnane:

I knew that I wanted to study laser science. Very fortunately, a new assistant professor, Roger Falcone, was starting a research group. The wonderful thing is that the labs were completely empty, so we had to order everything, and learn how to build high power femtosecond lasers and experiments. It was a new area of research and it was a perfect fit.

Zierler:

How did you go about developing your dissertation topic?

Murnane:

The goal of my thesis was to make a very fast X-ray source, and then to use it as a fast strobe light to capture very fast processes in materials. Since the mid to late eighties, scientists have explored different ways of making very fast bursts of X-rays to capture the motions of electrons, spins and atoms in materials and chemical reactions. The approach I used in my thesis was to use a high-power femtosecond laser to create an X-ray emitting plasma on a solid, that self-terminated after the solid exploded. At that time, I produced the shortest X-ray burst to date, at 1.1 +/-1 picoseconds (10-12 s) (laughter). And the other claim to fame was that I had built the most powerful femtosecond laser in the world to make the X-ray emitting plasma - producing five milliwatts.

I spent a few years building the laser and then figuring out how to make a very fast X-ray source, and then measure it so we could prove that the concept worked. As is usual with PhD research, the first laser designs and measurement techniques did not work. But we changed plans and eventually found routes to make it work and that was so exciting because it allowed us to be creative. The night the experiment finally worked, Henry and I were so excited. In a good PhD experience, graduate students have the opportunity to explore and make their own discoveries because that is when you believe you are a scientist.

Zierler:

What were some of the broader questions in the field that you felt your dissertation was responding to or contributing to?

Murnane:

In the intervening thirty years, the field has advanced dramatically. Scientists, and our current students, now have an ability to make measurements with attosecond (10-18 s) and even zeptosecond (10-21 s) precision. And scientific applications of ultrafast X-rays have blossomed, using tabletop X-ray sources and large-scale facilities. And one big advance we have pushed in the intervening thirty years is to develop bright, laser-like, X-ray beams. These have an advantage over the light-bulb-like X-ray sources that I demonstrated in my thesis, because the pulses are even shorter, and the beams are directed.

Zierler:

I’m sure you want to be humble, but these are significant scientific achievements. Can you talk a little bit about what it felt like to be able to accomplish this as a graduate student?

Murnane:

We were thrilled to have achieved our goal. The experience taught me that I do my best work when working with other people. At the time, the model for an experimental PhD degree was based on small groups where each student did a separate project, by oneself in the lab for the most part. My thesis project involved laser science, plasma and condense matter physics because the laser-excited material started as a cold solid and then transformed into a warm dense matter and then into a plasma. I quickly realized that if you really wanted to integrate all of these areas, you could make progress faster if you could put together a good team. My future husband, Henry, joined the group before we knew each other, and we were a very good team because we had complementary strengths. In a new field where much is unknown, the research works best in a discovery phase. In that situation, a small team with lots of interactions can outperform the same number of people working on separate setups. And our philosophy changed so that if we started our own research group, it would be based on smaller team because people have more fun and are comfortable attempting more challenging experiments. There is more serendipity and you can really drive progress faster.

Zierler:

Margaret, I wonder if at your dissertation defense, if it was the kind of defense where you really-

Murnane:

There is no thesis defense at Berkeley! (laughter)

Zierler:

No defense?

Murnane:

There’s no thesis defense. You just write it up, and the committee signs it. And then you go the graduation ceremony.

Zierler:

But, still. I wonder if given how you’re describing this; you knew more about this than your adviser and the committee did?

Murnane:

That is the point of a PhD, becoming the world expert on a topic.

Zierler:

Margaret, I wonder if your original plan was to return back to Ireland and-

Murnane:

There were very few positions for scientists in Ireland at that time. So, this was not an option.

Zierler:

So, you went to Berkeley, at least open to the possibility that you would make a life for yourself in the states?

Murnane:

Yes, although I didn’t have a concrete plan. And, in fact, I didn’t understand the system and culture well. Several times I thought that perhaps I wasn’t going to be happy as a scientist. But fortunately, by then I had met a wonderful peer group of women, and Henry. Many women in my class had similar experiences with the typical physics monoculture that prevailed. Henry was a great source of support, since he is also a first-generation college student whose parents had come over from Europe after the Second World War. He was born in the U.S., so he was a more attuned to the cultural issues, and he tried explaining the culture to me. All our careers are helped by the positive people we work with along the way.

Zierler:

That’s right.

Murnane:

I mean, this is not just in science. It’s in every field. And so, I was very fortunate to meet and still be collaborating with many people. This is what I always say to my own students: your peer group is an incredible resource. They’ll be the people you’ll be networking with when you’re trying to accomplish something big in your career.

Zierler:

And when did you meet Henry?

Murnane:

Henry joined the group a year after I did. I joined in ’83 and he joined in ’84.

Zierler:

And at what point did you realize this? The joke goes that you would be willing to accept the two-body problem.

Murnane:

We were- dating from ’84 on. And people said, “You know, you will never find jobs together.” But we hoped that perhaps one of us could work in industry. And the other person could find a university job. We were very fortunate that we were the first two students in the group. Our advisor Roger Falcone was so helpful. He got requests for reference letters for a search at Washington State University and he suggested, “Maybe you should apply.” So, we faxed our resumes and they said they wanted to interview us because they were trying to do a cluster hire in optics. And because Washington State University (in Pullman, WA) is geographically isolated, the university had a spousal hire program. So, it was fantastic, we got to Pullman and they had a great physics building and lab space. They were giving us a half a million dollars for to start up our research group, which was great. I don’t think another university would have hired a couple and allow them to do joint research. At the time, faculty thought, “Oh we’ve got to separate people to see who’s doing what, so we know they’re equally meritorious of tenure.” Also, as we left to take positions at WSU, some colleagues said to us, “Oh, don’t go. Because you’ll never be heard from again.”

Zierler:

Margaret, you mention that you thought one possibility might be to solve the two-body problem, one of you might enter industry. So, I’m curious with regard to your work, what might have been some of the industry applications that you might have pursued?

Murnane:

Photonics, electronics, semiconductor- there’s so much metrology based on light. But we had few contacts in industry, as was common in academic physics departments. In our own research group, if we can, we try to promote collaboration with industry, to build up a network so that the students who want to go to industry have good contacts and an alumni network. This approach is much more widespread these days.

Zierler:

Now relative to physics generally, you had a very short postdoc. I’m curious if that is standard in your field, to have such a short postdoc? Or the opportunity at Pullman just came about and you took it because it was so attractive.

Murnane:

Everyone’s career is different. I had done a master’s degree in Ireland and then a relatively long PhD because we had to build the lab up from zero. So, after a year postdoc, we got faculty positions. We are happy to get positions together because there was a mild recession at the time.

Zierler:

Now, were you hired to build the field at Washington State University? Or were you joining a group that was pretty well built up at that time?

Murnane:

There were around fifteen faculty in physics at WSU. So, we were hired to build up our own research area in ultrafast laser science. And the timing was fantastic because the laser technology was changing from dye laser to a much more robust, crystal-based, Ti:sapphire laser technology. We realized that the dye laser technology we had been using was very limited in the energy and power we could produce. So, we started to explore the new crystal-based ultrafast laser technology. These were perfect projects for our own students learning how to build lasers. And also, for young assistant professors, because we could publish on relatively quickly if we worked together. And I’m so grateful that WSU allowed us to work together because our competitors were big groups in Europe or big schools in the U.S. So, if we hadn’t worked together and learned how to do that effectively, we wouldn’t have been able to compete.

Zierler:

I’m wondering if when you got to Pullman that’s when you first realized that the rest of the world looked actually very different from Berkeley?

Murnane:

Yes. We were very happy in Pullman. We would often get faxes from people, cause we were helping people duplicate our group’s laser designs by either mailing them or faxing them the designs. Sometimes, we would get a fax back saying, “I’m going to a conference in Seattle. I’ll drop in to see you.” And then we’d have to fax back saying, “No, no, no. You have to buy another flight to get to Pullman, on the other side of the state…” (laughter). But most of the time, we had huge amounts of time because we could afford a house. We could walk to work. And there were very little distractions and wonderful outdoors. The Bitterroot Wilderness. The Salmon and Snake rivers.

Zierler:

Now in the relatively short five years that you were there, were you able to build up the lab and the program that you wanted to?

Murnane:

We built up an exciting laser program with our group, that helped many other scientists. We started to do our first experiments in coherent (laser-like) x-ray generation and get those published in good journals. It was a really amazing time. The students were amazing. Really amazing. And we were fortunate we got some NSF and other funding. So, one of the big reasons we left WSU was that at the time, the exam structure was very much around a traditional physics program where you would get very advanced questions on the comprehensive exams. This method of evaluation was common in many physics departments, but it did not suit all gifted students, depending on what type of research you’re trying to do, one needs diversity in personality and approaches. For example, deep knowledge, careful planning and exact calculation are great. But in a new field where the path forward is not obvious, then you need to also work with people who enjoy uncertainty and can add unexpected insight. And the problem is that often, people who are good at dealing with uncertainty and are creative in that environment are not great at very advanced mathematical problems that are given in traditional programs. So, a lot of the really creative people would fail out and I could not recruit people and have them fail out when I thought they were very deserving of PhDs. So, we wanted to be in a university, in a department, with a degree program that could promote students with a broader set of talents.

Zierler:

You took on graduate students during your time at Washington State University?

Murnane:

Yes, several - mostly PhD students.

Zierler:

And were you expecting to spend a longer amount of time there? How did the next opportunity at Michigan come up for you?

Murnane:

Yes. We expect to spend a long time at WSU. But just about the same time that we were very concerned about the narrow spectrum of students, then University of Michigan approached us to interview for positions at the Center for Ultrafast Optics, on the Engineering campus. So, we talked to our students, to see if they liked that idea and they did. And so, we moved-

Zierler:

Oh. So, you brought students with you?

Murnane:

Absolutely. Several. And then a big truck and packed up the lab and headed out. Headed east on New Year’s Eve in a snowstorm (laughter).

Zierler:

I’m sure your colleagues were quite sorry to see you go.

Murnane:

We understood the tradeoffs of a big school versus a small school. And we appreciated that WSU had allowed us to establish a career and a track record of working together. But, going back to my dad- what you teach, how you teach, and how students feel has always been important for me.

Zierler:

Margaret, you know, you’ve been at the cutting edge of this field since your dissertation days. So, I’m wondering, in the short amount of time going from Berkeley to Michigan, how had the field changed? And specifically, how had the basic research questions that you were asking and setting up experiments around- how did that change as well?

Murnane:

So, between Berkeley and Michigan, the era of ultrafast dye lasers for the most part ended- dye lasers were challenging to use since they changed every day because their chemical composition changed. The new crystal-based Ti:sapphire technology was starting to be adopted and we were part of the community pushing this new laser technology forward, pushing it to the fundamental limits to access new capabilities for science. We wanted to generate very short-duration X-ray sources – more than 1000 times faster than the plasma approach we explored for my PhD project – using a new approach called high harmonic generation (discovered in 1987). Using this high harmonic process, it is possible to convert laser beams directly into coherent (laser-like) x-ray beams.

Other scientists were interested in the same laser technology to probe very fast processes in materials, molecular and biological systems, engineering and medicine. The vibration period of the C-H bond is on order of ten femtoseconds, so people realized immediately that if you had very short pulses, that you could actually track chemical reactions, material transformations, and functioning systems.

Zierler:

Margaret, in what ways did moving to a much larger university confer advantages to you, your students, and your research? And in what ways were there challenges in not being in a smaller environment?

Murnane:

It was terrific learning experience to be part of an engineering department that was very different from physics. Henry had started a company at WSU in response to community requests for a “kit” for the ultrafast Ti:sapphire lasers that our group had developed. This was because at that time, the large laser companies did not sell lasers with very short, 10fs, pulse durations. At the University of Michigan, the tech-transfer office was helpful, and faculty were encouraged to start companies. This was dot.com era, when the computer scientists were writing few-page proposals for a million dollars (laughter). And they would tease us because we were writing these huge proposals to get smaller amounts (laughter).

I often joke that faculty should be required to do a sabbatical in a different college, because it opens up our minds to new ways of teaching and research. Sometimes we think it’s the technical gaps that are the most important. But I don’t believe that. I think it’s the social and the contextual gaps and how people approach problems are the much more interesting and important for innovation. To solve hard problems, you have to be able to work with people with very different backgrounds and views. However, we had a real problem at Michigan, because we were in the college of engineering. And at the time, the college had an amazing fabrication facility for making semiconductor materials and understanding them. But there were no instrument or electronic shops to build the instrumentation we needed. And we had limited access to the physics and chemistry shops that were two miles away. So, we were instrument builders, not able to build instruments.

Zierler:

Hmm.

Murnane:

However, the students and people were amazing. The person running the center was Gerard Mourou, who got the Nobel Prize in 2018 with Donna Strickland. Gerard was passionate for lasers. We were trying to make a transition from building lasers to using lasers.

Zierler:

Now in terms of writing proposals, Margaret, what agencies or foundations would you write to for support? And what were some of the recurring themes or exciting things that you would want to convey in your research that would convince them to support this work?

Murnane:

We were trying to get funding for the new field of strong field physics, and in our case, to explore high harmonic generation as a unique light source. This was challenging because at the time, it was “far out” or unfamiliar to other physicists. High harmonic generation is based on very beautiful quantum physics, where a femtosecond laser creates a nanoscale quantum antenna by sculpting the radiating electron dipole. However, it was new, and people though it was photonic engineering, and not quantum physics. One review of a rejected proposal said, “basic physics needs to be protected from this kind of research.” Now, many physicists are exploring and using high harmonic generation as a light source. And there are setups now in industry and national laboratories.

Zierler:

Now, again, you found yourself in Michigan for only three years. Had you expected to stay longer there?

Murnane:

Yes, absolutely. Henry really loved teaching semiconductor physics cause he could merge applications with quantum mechanics. But we couldn’t build instruments. And so, we were sitting in the square in Santa Fe while attending an APS (American Physical Society) meeting, and we were thinking, “How are we going to solve this?” And Dana Anderson from JILA happened to wander over and he said, “You guys look glum. What’s up?” And we said, “You know, we can’t build instruments.” And he said, “You have to interview at JILA.”

Zierler:

Yeah.

Murnane:

And at JILA- it’s whole thing is instrument building and atomic, molecular and light science.

Zierler:

I’m sure you were aware of all of the incredible work that was going on at JILA.

Murnane:

No. I had served on a review committee, but Henry had never visited.

Zierler:

But, somebody like a John (Jan) Hall, had you been aware of his work, for example?

Murnane:

Henry was well aware of Jan’s work. My research was at the intersection of condensed matter physics, new ultrafast laser science and plasma physics, so I was not as familiar.

Zierler:

In terms of your collaboration, given that it had such a multidisciplinary component, who were some of your key collaborators that might have been beyond the immediate field that you were working in?

Murnane:

In the early 2000s, after we went to JILA?

Zierler:

Correct.

Murnane:

We were very fortunate to have some long-term collaborations from Europe who were interested in the same quantum materials science that we were. In Europe, ultrafast lasers were embraced for such applications faster than in the U.S., where static probes were more widely used. In the U.S., ultrafast lasers were embraced by the chemistry community, but it took much longer for the material science and condensed matter community to be able to access these new capabilities. They would send their graduate students as postdocs to JILA for joint projects, to show what was possible. When you invent a new light source and hopefully you’ve invented it while talking to other scientists so it’s going to be useful, the fastest way to demonstrate utility is to collaborate with another world expert. And then that collaboration is what can really move things forward very quickly.

Now of course, these advanced laser and coherent x-ray technologies are being broadly adopted. It is exciting to see them used by industrial R&D, like IMEC (the premiere semiconductor R&D facility), and it’s just installed two of these high harmonic sources that KMLabs supplied to do very precise measurements of next generation materials. This timescale of around thirty years to have a new technology adopted for real-world applications is common.

Zierler:

Now, what exactly was your appointment when you got to Colorado? Was the sense that you would be dual headed between JILA and the department of physics?

Murnane:

Correct. At JILA, the fellows are either employed by NIST or by the University of Colorado faculty. Henry and I are University of Colorado faculty because Henry had started a small spinoff company and so, because of conflict of interest with commerce, neither of us could be a NIST employee.

Zierler:

And what were your impressions when you got to JILA? What was it like for you?

Murnane:

It was amazing because of the technical support. When we first moved, I didn’t go into my office for about three months because we needed to rebuild our labs. So, we had a wonderful time for the first four years or so, having time to spend in the labs with our students.

Zierler:

Did you take graduate students with you from Michigan or you built up, so again, you did?

Murnane:

Yes. They were very excited with the move, because they were instrument builders also.

Zierler:

Was it difficult for you to take on new graduate students at Michigan because of the difficulties with the building instrumentation?

Murnane:

The students at Michigan were excellent. And I was very fortunate to get a MacArthur Grant, and so we could use that money as matching funds for equipment grants. So, we were able to slowly rebuild our lab.

Zierler:

What was the culture of collaboration like at JILA? Was it a place where people would get together and discuss ideas even if you weren’t necessarily, specifically working with people?

Murnane:

Our field was new for JILA, encompassing applications of intense ultrafast lasers. The precision spectroscopy that JILA is famous for uses low energy ultrafast lasers. Some of the core technology was common, so in that technology we were able to collaborate with John (Jan) Hall and others. When we were at WSU, we had sent the laser designs to Steve Cundiff and his supervisor at Bell Labs, Wayne Knox (and thousands of others worldwide). And so, they had built that laser and Steve brought it with him to JILA and used that to demonstrate the frequency comb technology that John got the Nobel Prize for. So, some of the common core femtosecond laser front-end technologies were common. So, we did some collaboration, but we were really focused on high-power femtosecond lasers, their use for coherent high harmonic x-ray generation, and applications.

Zierler:

Margaret, after moving around so quickly, I wonder at what point you realized that JILA was just perfect for you and that this is where you would make a career long term?

Murnane:

We loved Colorado, and Boulder is amazing. The students are amazing. It is a great place to live.

Zierler:

And can you describe a little- in what ways does JILA allow you to do research and collaborate that is truly unique, that you couldn’t do anywhere else?

Murnane:

So, JILA has amazing instrument shops. We published several papers with our colleagues from the instrument shop as coauthors, because they contributed to some design aspects.

Zierler:

Margaret, I wonder if you can talk a little more broadly about the history of laser technology. I’m curious, have you been part of the improvements in laser technology or are you a beneficiary of those improvements and you’ve used it to advance your own research in the science in general?

Murnane:

We understood that to make very fast X-ray pulses, we needed very short laser pulses. So that’s exactly what we did at WSU, is to figure out the fundamental limits of this new solid-state laser technology which led to the first robust and useful ten femtosecond laser. There were several groups worldwide working to understand the fundamental limits of femtosecond lasers, so we kept each other on our toes. We didn’t patent our new understanding at the time, because when we went to the Washington State Patent Office, they were used to licensing the Cougar football’s logo, of the Cougars (laughter). So, they passed. But they handed over the rights, which allowed Henry to commercialize this technology. Before Henry started KMLabs, we also handed out the designs for free, to help other scientists. And those initial designs really helped the broader field transition from lasers that could operate on around one hundred femtoseconds timescale, to close to the single cycle limits. And that’s quite important in both ultrafast X-ray generation and in stroboscopic imaging of very fast processes. And the more we learn how to make measurements better, the more we see that this ability gives you an opportunity to see very fast processes and also to control them.

Zierler:

I wonder if you can talk a little bit about how your research, particularly being able to see how atoms move, is of interest more broadly beyond your specific field? What are the other kinds of scientists who are paying close attention to what you’re doing? And how is it relevant for their work?

Murnane:

Okay. So, there’s a number of different ways to answer that. But, let me give you a 40,000-foot answer that relates to something very practical.

Zierler:

Please.

Murnane:

Understanding heat transport at the nanoscale, that is relevant to designing efficient electronics, thermoelectric and next generation quantum devices. So, you might think that this research topic is old - that heat transport is driven by a thermal gradient, spreading diffusively from a hot to a cold region. However, it turns out when you look at how heat flows at the nanoscale, this is not true. In the past, scientists studied heat flow using visible lasers, with wavelengths (~500nm) much larger than the scale lengths in nanosystems (<1-100nm). The problem is, that if you use a visible laser to try to look at transport in something very small, you need a model to interpret the signal. So, you heat the material, look at the scattered light, and see a change, but you can’t see the heating and cooling directly. So, when we were studying nanoscale heat flow using shorter wavelength (~30nm) extreme UV (EUV) light, our students started to see some very surprising behavior. For example, what they saw was that if you had an array of nanolines or nanodots and you heated them, they cooled faster if they were placed close together. So, the thermal load per unit area was much higher, but the cooling was much faster. So, this seems like crazy. You know, that completely not diffusive, and even counterintuitive.

Zierler:

Sure.

Murnane:

It turns out that we uncovered a new regime where collective effects change how the heat flows. By packing hot spots more tightly, they appear like a uniform heat source, and this allows the lattice vibrations in the hot regions to better couple (i.e. transport heat) to the cooler regions. It took several years for us to work with theorists and to develop a fundamental understanding. But when our students first reported this new finding, some people commented, “You can’t be seeing what you’re seeing – you must be misunderstanding the data.” And then, a few years later they said, “Okay. We see the same effects now. But you must be misinterpreting them.” And now, several years later, people are starting to accept it. So, it’s a great example of, if you have a new tool, that’s well matched to the length and time scales of which you’re trying to see, one can uncover new understanding of nature relevant. And we have seen multiple new behaviors in magnetic and quantum materials, in warm dense matter, and in nanoparticles.

Zierler:

In what ways is your research, has it become perhaps, more relevant than in the early days to industrial or technological applications?

Murnane:

Absolutely. One of the reasons is EUV lithography. Technologically, the semiconductor industry is now using very short wavelength 13.5 nanometer light to make circuits with the smallest features. The understand how to optimize materials for next-generation circuits, they need tools that can see things on very short length and time scales. For example, one of the issues they are trying to solve is how to make very good photoresists to print very tiny circuits.

X-ray microscopes have been around for sixty years. But they’ve always been around ten times diffraction-limited (10x more blurred than the wavelength of the light) because you can’t make a perfect X-ray lens to focus the light. Microscopes based on visible light can reach a resolution of ½ their illumination wavelength or even smaller, because really good lenses are available there. So even though X-rays have much short wavelengths, it was simply not possible to take advantage of this. However, now that we can make laser-like (coherent) short wavelength beams, we can overcome this limit, by throwing out the lens. Instead, we use phase retrieval algorithms to extract the image from the light scatted by an object, and this has allowed us to make the first perfect EUV or X-ray microscope. So, we can image with spatial resolutions determined only by the wavelength of the illuminating light. And the nice thing about extreme UV or soft X-ray light, is it penetrates below the surface so we can image buried interfaces. That’s very important for quantum devices.

Zierler:

You cut out for a second there. The last thing I heard was, “So there’s both.”

Murnane:

Yes. There’s both interesting fundamental science questions and interesting and important applications in material science and nanotechnology.

Zierler:

Margaret, in looking over your incredible list of awards and honorifics, one that jumps out to me is the National Security Science and Engineering Faculty Fellowship. And that makes me wonder if your research has military or national security implications as well?

Murnane:

That fellowship was all unclassified research and it supported new imaging capabilities and mid-infrared lasers. We needed the mid-infrared lasers to push the photon energy limits of X-ray high harmonic generation, so that we could image thicker materials or cells in 3D at very high resolution. Of course, mid-infrared lasers are also really interesting for sensing other applications.

Zierler:

Margaret, I sense that you’re far too humble to allow me to ask you an in-depth level of questions about all of these honors and awards. But I wonder if you can share with me if any of them really stand out for you in your memory as being most satisfying personally or professionally to be recognized in the way that you have?

Murnane:

I think the joint awards with Henry are the ones we really appreciated because you can’t solve hard problems alone. Like coronavirus, diversity in STEM, the economy. We have to work together.

Zierler:

That’s right (laughter). Speaking of working together, not to get too personal, but I wonder if you can share a little bit about what it’s like to work with your husband. And by definition, you don’t have those boundaries between work and home. What are some of the challenges and what are some of the opportunities that you have found working with your husband over all of these years that have allowed you to really support each other’s research, and also celebrate and accept that you each have individual careers and aspirations, as well?

Murnane:

Well, think about farmers like both my grandparents, or families who ran small stores or restaurants, people work with their spouse all the time. It’s not new. The great thing about working with your spouse is that you will get honest criticism and hopefully learn how to accept that (laughter). You are a better person whether you’re running your farm or running a shop or a restaurant or a quantum science lab with someone who is a partner. And, who else will read your proposals? It’s a lot of hard work (laughter).

Zierler:

Margaret, coming from an international background, I wonder if you’ve used to your advantage, some of the work that’s being done in other countries for- just being aware of what other people in the field are doing or opportunities to collaborate. How might you have a broader perspective, perhaps, than some of your American colleagues about some of the fundamental work that’s been going on in your field beyond the United States?

Murnane:

I think we recognize it. Of course, the U.S. has many, many, many collaborative teams. I think to do very good science, it is good to move into new fields. Initially, people won’t accept you, but you can bring a fresh perspective. And so, the good thing about trying to go into new fields and following the careers of other people who’ve kind of wandered around in a sense, is to recognize when is the right time to address an old problem. So, the places where one tends to see issues in society and science is that if you have somewhat closed fields who don’t accept new people. Group think is a big challenge science and every aspect of society and our lives.

Zierler:

Margaret, to come back to something you said earlier in our conversation, that it really took you coming to the United States to think about or even to occur to you that there might be some unique challenges that women face in the sciences, that you never really thought much about in Ireland. Your long record of service to the physics community of course includes a very strong component, particularly with the APS, in supporting women in science. And so, I’m curious if you could reflect back-

Murnane:

I was following great footsteps from Judy France, Millie Dresselhaus. I mean, they were amazing leaders. By serving on committees in DC, we learned the ropes and we developed a network- and realized that many of same issues were being faced by many women around the country.

Zierler:

So, if you can reflect back, you know, to your early days of arriving in Berkeley and to where we are in 2020, particularly now that we’re at a moment in the physics community with #shutdownSTEM and a greater sensitivity and concern for underrepresented groups in physics. In what ways have challenges in the United States for women in physics, in what ways have they changed and improved since your early days coming to the United States. And in what ways do those challenges remain?

Murnane:

Yes, many challenges remain. For example, if you look at the percent grad students who are women in physics, it was around ten percent when I was a grad student. Now it is around eighteen percent So, I’m not a social scientist, but in my opinion, one thing that has not been appreciated is the importance of community. It is alarming that thirty to fifty percent of our top undergrads leave STEM because they do not feel welcome, and many of these students are top women or from underrepresented groups. We can fix this if we work together, to bring new insights and directions to science.

Zierler:

Right.

Murnane:

Universities have to stop focusing only on technical excellence because it is not the only important thing. There’s a whole social aspect of how we create welcoming learning environments, how we create the best research environments for innovation. The best research environment for the twenty-first century is not running multiple groups doing the same activity against each other as a race, perhaps neglecting important areas such as vaccine development. And our rewards are not set up to promote societal needs and solve problems.

Zierler:

Margaret, have you looked at yourself as a role model to some of your women students?

Murnane:

When I do talk to women, I talk about all the times that I messed up. And the wonderful thing is that some said, “Geez. You made all those mistakes and still succeeded?” (laughter) And that was great, because that’s the whole point. And if someone says they want to leave physics, I have often said, “Absolutely, if you find something else you really, really want to do, go ahead. But do not leave because the system wears you down.”

Zierler:

Right. Right.

Murnane:

Nobody else can determine your life.

Zierler:

That’s great advice. That’s great advice no matter who you’re giving it to. Margaret, one aspect of your career we haven’t talked about yet are your accomplishments in the classroom, both as a teacher to undergraduates and as a mentor to graduate students. And so first, I’d like to ask, for undergraduate teaching, what have been the most fun classes, the most meaningful classes for you to teach undergraduates?

Murnane:

I had the most fun when I taught classes that fulfilled science requirements, such as Light and Color or How Things Work. I really enjoyed teaching photography and architecture majors, helping students realize how, for example, light and color related to photography or architecture. We have many online tools and demonstrations that help the students to start interacting and having fun, so that they had a good memory and it positively affected their career. I remember once I was sitting at the back of the class and a student came up and he said, “You know, you’re not like a professor.” And I said, “Yeah?” “You don’t talk like a professor. You don’t look like a professor.” And the fact that he was totally willing to talk about this, I thought, “Yay! This is kind of what I want.” Because, you know, you don’t want them to go away thinking, “I hate science.” You want them to go away thinking, “I was able to access science and connect it to my major…”

Zierler:

Now on the graduate side, you know, I don’t want you to name names, but you’ve had so many graduate students over the years, and particularly watching them in a laboratory experimentation environment. I wonder if you could talk a little bit about some of the shared attributes that your most successful graduate students have exhibited?

Murnane:

They’re all super smart- smarter than I am. We get around 1000 applicants for grad school in physics to the CU Boulder PhD. We try to design the program to match classes and research projects to the student’s interest. So, whether they want to end up in a national lab or in industry or in academe, we try to expose grad students a few different types of projects so that they’re flexible and versatile. And, we try to create a community where people are teaching and helping each other, instead of just competing. So, some of the most successful students are the ones who realize that they have an incredible resource. And they realize that we’ve got this amazing group of people. To train leaders, they have to be a broader than just technical experts.

Zierler:

And what are the kinds of career advice tips that you give your graduate students, both in terms of the most exciting and promising fields to pursue the way that they should structure their postdoc experience? What are the kinds of advice that you give that are relevant to all of your graduate students no matter their background or their skills or their particular areas of interest?

Murnane:

Build a trusted network over time.

Zierler:

Margaret, for the last part of our conversation, I want to ask a few broadly retrospective questions and then a final forward-looking question. So, the first is, looking over the course of your career, are there any discoveries or advances in the instrumentation that stick out in your mind as being most fundamental in advancing the science?

Murnane:

So, that question depends on what kind of scientist you are. Isn’t that right. So, what’s fundamental to one is applied for the other. I had this great experience once doing strategic planning for The Optical Society and they put a bunch of us from industry and national labs and universities and they said, “So, on the spectrum, can you say where does your research lie- going from fundamental to applied, can you put yourself on that?” And we all put ourselves in the middle (laughter). That was a really great exercise to illustrate what the problem is. And some people use it as a sword, by saying “Oh, that research is too applied (impure).” This is just a human tendency. Most forward-looking reports miss the next breakthroughs, and many tools turn out to be revolutionary, electron microscopes, lasers etc.

Zierler:

Margaret, it speaks to your humanism and your generosity as a mentor that you are willing to share some of the mistakes that you’ve made over the course of your career as a way of giving confidence to your students. And so, I wonder if I could put you on the spot and ask you what mistakes you made that you use to most positive and productive result to improve yourself as a scientist, as a researcher, as a teacher?

Murnane:

It’s not the example I gave my students but rather the ones that influence me?

Zierler:

Correct.

Murnane:

I think my main gap was underestimating engineering. Because physicists often assume engineering is trivial.

Zierler:

Margaret, for my last question. Using your powers of extrapolation and given the fact that you’ve been involved in so much cutting-edge research over the course of your career, looking to the future, what do you want to accomplish personally in the field of experimentation and research? And what are some of the broader unanswered questions in your field that you’re most excited to contributing to?

Murnane:

So, we’re very excited about building powerful real-time microscopes that can make 3D nanoscale and even Å-scale movies. Seeing is understanding. And in proving out better ways to engage a broad and diverse set of students in STEM. And in revitalizing the physics graduate experience to better prepare trainees for technical management and leadership, and the ubiquity of data science. We are all drowning in data.

Zierler:

Well, Margaret, on that note, it’s been an absolute delight speaking with you. You’re incredibly generous to spend this time with me. And you have shared a wealth of insight and experience that really is going to be an important and unique addition to our oral history collection. So, I really want to thank you for this time together.

Murnane:

And I so much appreciate your patience with me and allowing me to ramble on as I often do (laughter).

Zierler:

Not at all.