Associate Professor Carol Hirschmugl
	cjhirsch@uwm.edu Telephone: (414) 229-5748 Room: 430

Carol Hirschmugl studies the interactions between infrared light and condensed matter, focusing on the low-energy dynamics of molecules adsorbed on metallic surfaces. Results from her research have revealed a complex interplay between the electrons in a metallic substrate and the vibrations in molecules adsorbed on the surface. For example, Hirschmugl found that when certain vibrations of the adsorbate relax (decay), they create electronic excitations in the metal. Previously, it had been believed that these decaying vibrations would only create other vibrations.

These discoveries were facilitated by using infrared radiation from a synchrotron, where a tight cone of light is produced from relativistically accelerated electrons. Unlike laser light, synchrotron light is simultaneously emitted at all spectral frequencies--from infrared light to x-rays. In the infrared, the emitted light is brighter than the sun. In Hirschmugl's previous work, she pioneered the use of the brightest infrared sources in the world at Brookhaven National Laboratory (Long Island, New York) and the Lawrence Berkeley National Laboratory (Berkeley, California).

Another advantage of this unique source of infrared radiation is that it is pulsed, providing the only known source of sub-nanosecond to nanosecond broadband infrared pulses. Thus, the evolution of low-frequency processes that happen on this time scale (such as certain interactions between vibrations in adsorbates and electrons in the substrate) can be directly probed. Hirschmugl is presently active in a program at the National Synchrotron Light Source where a visible light laser pulse is used to excite a system, and the infrared pulse from the synchrotron probes the system.

These powerful spectroscopic tools can also be brought to bear on other kinds of surfaces; in the future, Hirschmugl will apply these techniques to oxide and semiconducting materials, in addition to metallic substrates. This will allow technologically and environmentally relevant problems to be pursued and issues such as the stability, reactivity, and mobility of adsorbates can be addressed.

The synchrotron light can also be efficiently coupled to a microscope, making it possible to spatially resolve infrared absorptions on a micron scale length; previously only a spatial resolution of 10's of microns could be achieved. Thus complimentary, non-destructive studies of environmentally and technologically important systems will also be pursued.

She has received the University of California President's Postdoctoral Fellowship to work at the Lawrence Berkeley National Laboratory, and an Alexander von Humboldt Stiftung to do research in Berlin, Germany. She is an author of close to 30 publications, and has given invited talks on Infrared Synchrotron Radiation and its applications to Surface Science in Europe and the United States.