Chemical Physics and Physical Chemistry
Description
Physical chemistry at Penn aims at developing a fundamental understanding of the structure, dynamics and reactivity of molecules in different phases of matter, using modern theoretical and experimental techniques. These efforts often motivate the development of new experimental techniques and theoretical methods. Experimental physical chemists in the department study the dynamics of molecules ranging from large biological complexes to single molecules, including transient species and molecules in the atmosphere and on surfaces, the properties of condensed phase materials, and the molecular biophysics and structure of membranes.
The structure and stability (in kcal/mol) of peroxynitrous acid (HOONO), a secondary product of a key atmospheric reaction between OH and NO2, is characterized using infrared action spectroscopy. HOONO is identified in trans-perp (tp) and cis-perp (cp) configurations in a supersonic expansion, where OH overtone excitation provides sufficient energy to break the peroxide bond, enabling sensitive ultraviolet (UV) detection of the OH photofragments. The cis-cis (cc) conformer is not observed because overtone excitation falls short of the energy required for dissociation. Lester Group
