A waterfall of possibility: probing liquid flatjets with photoelectron spectroscopy

Liquid-jet photoelectron spectroscopy allows measurement of the electronic structure of liquids in a vacuum. However, the technique has only been applied to cylindrical liquid jets, whose curvature means measurements must average over the many orientations of surface molecules.

Stemer et al. developed a method to extend photoelectron spectroscopy to liquid flatjets created by the impingement of two cylindrical jets. The thin, planar surface of these flatjets opens new experimental possibilities.

While flatjets themselves are not novel, applying photoelectron spectroscopy to them is. This technique allows researchers to study the evolution of the chemical reactions and associated electronic structure changes occurring between the impinging solutions as they make contact and travel through the vacuum.

Probing both sides of the flatjet, the authors found that these two solutions never fully mixed and instead formed a stable liquid-liquid interface. X-ray emission spectroscopy can readily access this interface, but photoelectron spectroscopy will require thinner flatjets.

“This new system has the advantages of both a flat surface and an interface between two liquids,” said author Dominik Stemer. “It opens the door to many new things that wouldn’t be possible previously in photoelectron spectroscopy. You can now look at these newer and more complicated systems where there’s a lot of unanswered questions.”

The authors hope to manipulate the outer interface between the flatjet and the air. To do so, they must be able to control the surface molecules’ orientation.

“Eventually, I hope to be able to manipulate that geometric molecule structure at that interface with an electric field, which would be crucial for exploring chemical reactions in the atmosphere,” said author Bernd Winter.

Source: “Photoelectron spectroscopy from a liquid flatjet,” by Dominik Stemer, Tillmann Buttersack, Henrik Haak, Sebastian Malerz, Hanns Christian Schewe, Florian Trinter, Karen Mudryk, Michele Pugini, Bruno Credidio, Robert Seidel, Uwe Hergenhahn, Gerard Meijer, Stephan Thürmer, and Bernd Winter, Journal of Chemical Physics (2023). The article can be accessed at https://doi.org/10.1063/5.0155182 .