In this and previous work [D. J. Clouthier, J. Chem. Phys. 141, 244309 (2014)], the spectroscopic signatures of the X2BY (X = H, halogen, Y = O, S) free radicals have been predicted using high level ab initio theory. The theoretical results have been used to calculate the electronic absorption and single vibronic level (SVL) emission spectra of the radicals under typical jet-cooled conditions. Using these diagnostic predictions, the previously unknown F2BS and Cl2BS free radicals have been identified and characterized. The radicals were prepared in a free jet expansion by subjecting precursor mixtures of BF3 or BCl3 and CS2 vapor to an electric discharge at the exit of a pulsed molecular beam valve. The 2A1-X̃2B2 laser-induced fluorescence spectra were found within 150 cm-1 of their theoretically predicted positions with vibronic structure consistent with our Franck-Condon simulations. The 2A1 state emits down to the ground state and to the low-lying 2B1 excited state and the correspondence between the observed and theoretically derived SVL emission Franck-Condon profiles was used to positively identify the radicals and make assignments. Excited state Coriolis coupling effects complicate the emission spectra of both radicals. In addition, a forbidden component of the electronically allowed B̃-X̃ band system of Cl2BS is evident, as signaled by the activity in the b2 modes in the spectrum. Symmetry arguments indicate that this component gains intensity due to a vibronic interaction of the 2A1 state with a nearby electronic state of 2B2 symmetry.

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Published in The Journal of Chemical Physics, v. 142, no. 12, article 124301, p. 124301-1 through 124301-11.

Copyright 2015 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.

The following article appeared in The Journal of Chemical Physics, v. 142, no. 12, article 124301, p. 1-11 and may be found at http://dx.doi.org/10.1063/1.4915126

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The research of the Clouthier group was supported by the National Science Foundation. P.M.S. would like to thank the Clouthier group for hosting his sabbatical leave.

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