Hot bands in the <f>A˜←X˜</f> spectrum of HCBr

Spectra of both the <f>A˜</f>(0, 0, 0)–<f>X˜</f>(0, 1, 0) and <f>A˜</f>(0, 0, 0)–<f>X˜</f>(0, 0, 1) bands in the <f>A˜</f>–<f>X˜</f> band system of HCBr have been recorded and rotationally assigned. The HCBr radical was formed by 193 nm excimer laser photolysis of bromoform. We found no signals from HCBr when the photolysis laser wavelength was changed to 248 nm, although strong CH product emission was observed by eye at both wavelengths. Most of the spectra were recorded in absorption at ambient temperature in a long-path absorption cell using a single frequency Ti:sapphire laser as the light source, but some congested sections were recorded under jet-cooled conditions. Analysis yielded accurate values for the vibrational fundamentals and rotational constants for the vibrationally excited ground state levels determined. A combination of experimental measurements and ab initio vibration–rotation constants was used to estimate equilibrium parameters and a ground state structure for HCBr. [Copyright &y& Elsevier]