Direct IR Laser and Double Resonance Absorption Spectroscopyin Slit Supersonic Jets: Vibrational Dynamics of Novel Molecular Clusters

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With support from the Experimental Physical Chemistry Program, Professor Nesbitt is investigating the spectroscopy, structure, and dynamics of jet cooled, weakly bound molecular complexes. This work exploits high resolution spectroscopic information on vibrational transitions to help characterize and understand the weak molecular forces so crucial to a variety of chemical, biological, and physical processes. Using a combination of high sensitivity differential beam absorption techniques with multipass infrared probe geometries and pulsed slit valves for long pathlength absorptions, Nesbitt's laboratory is measuring high resolution, sub-Doppler vibrational spectra of various jet cooled complexes. Systems being studied include van der Waals and hydrogen-bonded dimers, dimers of polyatomic molecules, and diatomic molecules bound to several rare gas atoms. Rotationally-resolved vibrational overtone motions are being pumped and characterized by infrared-infrared double resonance techniques in hydrogen-bonded complexes and the resulting photofragments probed for internal state distributions. Intermolecular potential information for multidimensional potential surfaces is being extracted using quantum mechanical simulations of the observed high resolution spectral data.