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Oral History Transcript — Dr. Chun Lin

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Interview with Dr. Chun Lin
By Gary Cameron
In Dallas, Texas
October 14, 2008

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Chun Lin; October 14, 2008

ABSTRACT: In this interview Chun C. Lin discusses topics such as: University of Oklahoma; microwave spectroscopy; collision theory; electron excitation; Arthur Phelps; Robert Varney; Leonard Loeb; atomic and molecular physics; John Van Vleck; Will Allis; Leon Fisher; Ben Bederson; Gary Weissler; University of Wisconsin, Madison; American Physical Society.

Transcript

Cameron:

Iíve been letting people start with their own reminiscences about the GEC, how they became involved first, experiences at meetings, that sort of thing.

Lin:

OK, how did all this start? I was at the University of Oklahoma doing research in microwave spectroscopy, which almost had nothing to do with GEC. I shared an office with Bob St. John. Bob had been going to GEC for a number of years by then.

Cameron:

About what time was this?

Lin:

That was in the late í50s. I knew nothing about gaseous electronics. Bob gave a seminar on his research on excitation of atoms by electron collision, and when I heard that seminar, I realized that it was just a perfect place to apply quantum mechanics of collision theory. At that time I think I was somewhat familiar with that topic. So we talked about it. Just about that time Bob was running into a very interesting observation when he was doing electron excitation. He measured cross-sections of excitation into various energy levels of the helium atom. Some of the levels that he studied were supposed to have small cross-sections. But the observed cross-sections were much, much larger than what he anticipated and what the general belief was at the time. I felt that we should look into the quantum mechanics of those energy levels more carefully, and it just so happened that I was pretty familiar with it. So we worked together, found a solution to the problem and resolved the mystery. Naturally he wanted to present it at the GEC. I believe that was in 1960. He asked me to come, and I said of course Iíd like to. That was my first GEC at which we reported the work. I think thatís how it all started. Then it became more interesting as the program evolved. At the time, Bob had research support from the Air Force Office of Scientific Research. Since they were interested in the topic, we requested a larger grant, they agreed to it, and I became a regular participant of that project. Since then, Iíve been going to most of the GECs.

Cameron:

When was your first meeting?

Lin:

I think 1960.

Cameron:

At that time, do you remember any particular sub-field of gaseous electronics that was really dominating the meetings?

Lin:

Not so much dominating as to maybe a part of the major activity. At that conference there was no parallel sessions. There were not that many papers. The field of gaseous electronics had people working on discharges of great complexity, and there were people working on different kinds of discharges. The paper of Bob and myself was in the session called Basic Processes, in that it dealt with the underlying microscopic processes. These are the fundamental processes from which things went up in complexity. We worked more on the atomic physics side, whereas other people were working on what is sometimes called the collective behaviors.

Cameron:

At that time, people were primarily interested in fundamental theoretical work?

Lin:

No, just our little niche.

Cameron:

What about the other presentations in those days?

Lin:

I canít remember now. Of course there is a bulletin listing all the papers. I was a newcomer and I didnít really know too much about ďcollective behaviorsĒ. For example I talked to Art Phelps since he also had encountered that problem of helium cross-sections larger than what they were thought to be. I talked to a relatively small number of people specializing in that kind of things. Actually, there must be a lot of other people working on whatís called atomic collisions, but they didnít come to the GEC probably because they are not aware of such an area of application. As the conference grew, we drew in more and more people on fundamental processes, and thatís how it developed.

Cameron:

The reason I asked that question was when I was talking to particular Fisher and Varney this summer, they said that initially they wanted to keep the GEC conference about theoretical work as opposed to applied work, but I sense that there was a gradual shift, or maybe I should say expansion.

Lin:

What is called theoretical can be conducted with different emphasis. For instance, in what I call collective behaviors, the electron scattering happened first, and then something else developed. Now, those are theoretical in the sense that you donít do an experiment to pull it out. You see some radiation coming out, then you try to piece things together and say well it must be due to A, and then followed by B, followed by C, and so on. That is one theoretical approach. Now you go down to the next step. From A to B, why is it more likely? Why could it not be A to B prime, and then from B prime to B? Is it reasonable? There you need a quantitative calculation. You really have to know the quantum mechanics of the atoms involved, and thatís where I came in with this one process to understand whether this is the correct way to look at it. We determined that it wasnít the correct way, so we had to make some improvement. Itís just that what I was doing was more microscopic than Varney.

Cameron:

At that time, you were at a university?

Lin:

I was at the University of Oklahoma.

Cameron:

The majority of people that Iíve interviewed so far were involved industry in some way.

Lin:

Correct, because that stuff is useful.

Cameron:

At Oklahoma, you were a professor? [Yes.] Did you have funding problems for your research?

Lin:

Research style was different at that time. It is possible to do research with a very minimal amount of funding. In the first work I did, I only need paper, pencil, and a desk calculator. I pushed the keys; whoop, whoop, whoop, the numbers came out. My first piece of work was not supported in that sense. Itís only when St. John and I decided this is an opportunity to expand, we ought to do more, then we requested additional funding. That was also after the beginning of the space program, when research was expanding, and the funding people recognized the need. Just knowing something per se is important. That was really terrific.

Cameron:

It was sort of the golden age ofÖ

Lin:

Golden age both on research funding and the spirit of doing research — do it for the sake of knowing the answer as opposed to some other auxiliary consideration. Had I been conscious of writing progress reports and all that, I may not have had so much fun with my work.

Cameron:

Where did you get your education?

Lin:

I was an undergraduate at the University of California at Berkeley. You might have run into the name Leonard Loeb. I took my first course in atomic physics under Loeb. After I graduated, I went to Harvard for my graduate work. I did my research under John Van Vleck in theoretical physics. So I had nothing to do with gaseous discharge. After graduating from Harvard I went to the University of Oklahoma where I started a program on microwave spectroscopy. With funding by NSF, I was busy building a microwave spectrometer. After talking to Bob St. John about his experiments on electron excitation of helium, I became involved in that project too.

Cameron:

Itís interesting, because I think you are one of the first of the second generation of members of the GEC.

Lin:

I would think so, yes. And others came at the time of expansion. When I ran into Loeb at the GEC, I introduced myself. He was very pleased to see somebody from his course had gotten into that area.

Cameron:

The vast majority of people Iíve interviewed so far have been connected with MIT and that group there.

Lin:

Will Allis was the key figure at MIT, but my connection with him was not through GEC. He was a friend of my major professor at Harvard, Prof. Van Vleck.

Cameron:

I must say, Harvard and MIT are very close.

Lin:

Yes. They lived quite close to each other. They were not exactly neighbors, but were long-time friends.

Cameron:

In a certain way one would think there was competition between the two universities, but was there also cooperation between them?

Lin:

I think there was virtually no gaseous electronics in that sense at Harvard, and even though Van Vleck and Allis were good friends, there was almost no overlap in their research interest. Van Vleck often referred to the GEC as the Allis conference.

Cameron:

And he basically ran the conference for a number of years.

Lin:

Oh yes. When I first attended, I think he was the honorary chairman, and he was for many years.

Cameron:

Just personally, what were some of your earlier experiences like, going to the GEC conferences?

Lin:

I was given a chance to talk to Loeb, and then I met the earlier generation. Rob Varney, a person I met at the first GEC I attended. And another man called Gary Weissler, who was a professor at the University of Southern California.

Cameron:

I donít see him. He was probably not at the first conference.

Lin:

No, he was not.

Cameron:

The only names I have are for the very first conference.

Lin:

Speaking of that conference, if you have a chance, you ought to talk to Ben Bederson. He was Leon Fisherís graduate student at NYU, and he attended the first GEC.

Cameron:

He was on my list for the summer, but the scheduling didnít work out.

Lin:

Ben has lots of interesting things to tell. I met Varney and Weissler whom I saw a lot later on. They were both graduate students of Loeb, so I met the Berkeley branch of GEC people. Since the first one I went to, I missed very few. The í60s was an expanding time. More and more people came to GEC, and they began to have parallel sessions. I got to meet more people on more of the collective behaviors side; it was very helpful to know them. Some of them applied cross sections to other areas such as atmospheric phenomena. I remember running into Prof. Otto Oldenburg. He was a professor at Harvard. We had a very nice chat, talking about old times, of course. Then I moved to the University of Wisconsin in 1968. We offered to host the GEC, so we had the conference in Madison. The first one we had there was 1973. By then the conference had grown quite large.

Cameron:

Seems like the early conferences were relatively small, very homogenous. [Yes.] Then by the í60s it just started to expand. [Yes.] Iíve been trying to ask how many people here how many people at this conference today. Itís in the hundreds, it must be. [Yes.] Someone commented that one of the biggest things they noticed about the differences between GEC early on and today is just this whole idea of having concurrent session. They thought that it made things a lot more difficult in trying to really understand everything thatís going on.

Lin:

Yes. We had single sessions, and then for many years doubles, and now we get three. And that makes it more divided. You want to hear all the papers in your own sub-field, and then you donít get to go to the others. Itís a dilemma all the conferences are faced with. Youíd like to get more people, but then you have to accommodate them. In the early days, there were no poster sessions, and now the posters help to ease the load. There is still no substitute for person-to-person communication. In a poster we read the thing thatís there, but itís no substitute for hearing a good introduction, telling us why the authors did this, how was the work motivated by such and such. They may have stated it in the poster, but itís not the same as hearing it in a talk.

Cameron:

A number of people Iíve interviewed so far, their first GEC meeting was as a graduate student, but you were already a professor.

Lin:

I was already a professor. Iím trying to remember if my colleagues in Oklahoma brought their graduate students. Before I started, I believe it was like this. In those days, there wasnít a lot of travel money. If you can go to a meeting by driving a car, you can take more people, and they double up and triple up in hotel rooms. But if you are thinking about flying and paying roundtrip airfare for graduate students, it would be difficult.

Cameron:

I assume you had graduate students of your own later on? [Yes.] And I also assume you encouraged them to attend meetings and so forth.

Lin:

I took them even in the early í60s. Maybe we drove. For instance, there were meetings in Colorado — surely we could drive from Oklahoma to Colorado. I think thatís what we did with Bob St. John. To places farther away we had to fly, and then it would not be easy. Maybe just bring one student.

Cameron:

Was there a selection process that you used? Or did you try to give everyone an opportunity?

Lin:

Of course there is another thing, too. In order to go to the meeting, the student had to have already obtained some pretty substantial results, write an abstract well in advance to be sure we got something worthwhile to report. So when you take that into consideration, and the possibility of alternating different years, and from time to time you do have the opportunity to drive, thereís no problem. I never felt that I had slighted any student.

Cameron:

I ask that because Iíve asked previous interviewees about their experience as a student, and then itís interesting to see it from a professorís point of view, bringing their students. I assume you thought it was important to go to conferences like this to give them the experience of presenting.

Lin:

Yes, oh yes, to give them the chance to know how their own work is really an essential part of the big picture. When you were a graduate student, you work on some ďlittleĒ problems day and night, and pretty soon you forgot that it is a very key element to a much broader area. Also they see more applications. Itís a very good educational experience.

Cameron:

Also, conferences like this were places to meet people from industry where these students could potentially find employment.

Lin:

Yes, very much, for sure. Now, the funding level has gotten to the point where they do support student travel; in fact funding agencies regard supporting students to attend meetings as an important component of the budget.

Cameron:

Of people youíve met at the GEC, who would you regard as the five most influential?

Lin:

Maybe the word influential is not the right choice. First, in your beginning phase of your career, guidance and advice from people who are experts in your field are more important than when you are more established. So the people I name arenít necessarily the ones I met in my earlier career. With this qualification I wouldnít call them influential, but I learned a lot from them. Ben was one. Will Allis and Leonard Loeb. Of course my collaborator, Bob St. John, he was the one that introduced me to the field. He was only a few years older than I. Yes, Iíd say those ones.

Cameron:

Thatís pretty much a universal list: everyone mentions the same people. Actually something that Art Phelps left with me that he came up with is a list of what he thought were some of the most important scientific advances that came out of the GEC meetings. Maybe you can comment on some of these.

Lin:

Yes, those are very familiar names. Art Phelps has a much broader perspective of the field than I have. I notice the names, but I donít think I can really single out any or put them on a comparable weighted list, but surely those are all important.

Cameron:

What would you regard as some of the most important advances?

Lin:

I cannot really nail down specific pieces of work, but the general concept that one needs to have detailed microscopic understanding of the processes, and how they are related to technical applications was the most important message to get across. Especially as technological advances evolved, their importance became more apparent. Then another kind of microscopic understanding became important that had not received much attention before. So I think these continual advances in technology along with a continual increase of linkages into microscopic understanding atomic physics are some of the most important advances.

Cameron:

Any particular meetings stand out in your mind as being not necessarily scientifically important, but just interesting on a personal level?

Lin:

There must be some, but now that you ask meÖ If there were, somehow I think I would have remembered. So I would say that there were ones at various times I thought really terrific, but then gradually more and more came up so that by now I really cannot pull out anything.

Cameron:

Do you have anything else you can think of?

Lin:

No, I canít think of anything. Iím very pleased to see somebody wants to put the history together. It will be very helpful to have. Iím glad to see that youíre putting in the effort to do all this.

Cameron:

One question I just thought of, someone said that you have been collecting a lot of the bulletins.

Lin:

Yes, I thought I had a complete set, but then I moved my office from one building to another. Iím sure it is still here, but one of them is missing. Itís got to be somewhere, but you know, if you canít find it, it isnít any better. So now I have to say that there is one I donít have. But other than that, I have the full set.

Cameron:

That is one of my suggestions to the group working on the GEC history, is that it would be really helpful to have something on that.

Lin:

Yes. Youíre talking about wanting to put it together, and now I think I have the set, and of course heís welcome to copy it, but he must to find a nondestructive way to copy.

Cameron:

I was going to suggest trying to scan them and do digital copies.

Lin:

If he could find a way to scan without tearing those books apart, I think thatís a very worthwhile thing to do. Especially one thing you ought to be aware of is that for many years the GEC had an option, namely, if I submitted an abstract, I can elect to have it published in the Bulletin of American Physical Society or not. If I want to do that, I have to pay something extra. A good number of authors chose not to do that. In the Bulletin of the American Physical Society, every year they do have a section on GEC, but that was not a complete listing of all the papers. Then the policy changed (I donít remember when), and after that every abstract got reproduced. Now today it was reproduced ahead of the conference, but in those days during the conference you were handed a book with all the abstracts there, and only several months later those abstracts would appear in the Bulletin of the American Physical Society.

Cameron:

Well thank you.