15min:

M. DESELNICU, C. TAO, C. MUKARAKATE AND S. A. REID, Department of Chemistry, Marquette University, Milwaukee, WI 53201-1881.

We report a comprehensive new study of the electronic spectroscopy of the A¹A''-X¹A' system of CHBr and CDBr in the region 450-750 nm. For each isotopomer, more than 30 cold bands in the progressions 2₀ⁿ, 2₀ⁿ3₀^m (m=1-3), 1₀¹2₀ⁿ,and 1₀¹2₀ⁿ3₀^m (m=1-2) were observed, in addition to a number of hot bands. The spectra were measured under jet-cooled conditions using a pulsed discharge source, and rotationally analyzed to yield precise values for the band origins and rotational constants. The derived A¹A'' state vibrational intervals are combined in Dixon plots with the results of Sears, Muckerman, and co-workers to derive barriers to linearity for the 2ⁿ, 2ⁿ3¹, and 2ⁿ3² progressions. The A¹A'' C-H (C-D) stretching frequency was determined for the first time, and is in excellent agreement with the predictions of ab initio electronic structure theory. The observed ₃ dependence of the CH⁷⁹Br-CH⁸¹Br isotope splitting in the A¹A'' state is also in excellent agreement with theory.