The Millimeter- and Submillimeter-Wave Spectroscopy of Low Temperature Collisions

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In this project supported by the Experimental Physical Chemistry Program of the Chemistry Division with funds for equipment provided by the Office of Multidisciplinary Activities, De Lucia and Herbst investigate the spectroscopy of low energy molecular collisions and of the interactions which govern them. Experimental studies of pressure broadening, pressure shifts, and state-to-state rotational energy transfer rates will be conducted using millimeter and submillimeter spectroscopic techniques coupled with collisional cooling and molecular ion production methods. The experimental data will be compared with results from modern quantum chemical and scattering calculations. Systems of interest include CO-He/H2, H2S-He/H2, and HDO-He/H2 as well as ionic systems HCO+-H2, CO+-He, and NO+-He. These results will help give insight into collision phenomena which occur most visibly at low energies and which are highly dependent on the shallow, long-range attractive potentials between molecules. The results of this program have relevance to atmospheric chemistry and astrochemistry, where interactions involving collisions between atoms molecules and ionic species at low temperatures predominate. Under these conditions the types of molecular cluster species under study here form readily.