HIGH-RESOLUTION INFRARED SPECTROSCOPY OF JET COOLED HCBr SINGLET BROMOCARBENE DIRADICAL

Abstract

First high-resolution mid infrared rovibrational spectral data on jet cooled bromocarbene (HCBr) diradical are obtained using quantum shot noise limited laser absorption methods. The HCBr diradical is generated by coflowing bromoform (HCBr3) in a mixture of Ne, He, and H2 through a pulsed slit discharge beam source and is subsequently cooled down to approximately 40 K in a slit-jet supersonic expansion. Interestingly, optimization of the HCBr radical requires the presence of H2, presumably due to decomposition of HCBr3 by H atom chemistry in the discharge. Rotationally resolved absorption spectra of the CH stretch ν1 = 1← 0 fundamental are analyzed, resulting in precise determination of ground and excited state rovibrational constants for both Br and Br isotopologues. The results for the ground state are in good agreement with previous high resolution near IR electronic studies in the Sears groupa. The ν1 band origin is now unambiguously assigned at 2799 cm−1, which agrees well with previous LIF/dispersed fluorescence studies of Reid and coworkerb.