15min:

BRANDON S. TACKETT AND DENNIS J. CLOUTHIER, Department of Chemistry, University of Kentucky, Lexington, KY 40506-0055.

The A²A' - X²A'' electronic transition of the HPBr free radical has been observed for the first time by laser induced-fluorescence (LIF) spectroscopy in the 480 - 430 nm region. HPBr and DPBr were generated in a pulsed discharge jet using a precursor mixture of PBr₃ and H₂ or D₂ in argon. At low resolution the bands have the characteristic rotational contour of a perpendicular transition of an asymmetric top, and a band-dependent bromine isotope effect in an approximate 1:1 ratio of HP⁷⁹Br and HP⁸¹Br. The analysis of the spectra, rotational constants, vibrational frequencies, molecular geometries and the results of ab initio calculations of the molecular parameters will be discussed.