Laser-excited resonant isotopic V→V energy transfer: H35Cl–H37Cl, H79Br–H81Br, D35Cl–D37Cl, and D79Br–D81Br

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Abstract
An isotopically selective transverse discharge chemical laser coupled with infrared fluorescence techniques is used to measure vibration‐to‐vibration energy transfer rates between v=1 levels of the isotopic species H 35Cl?H37Cl, H 79Br?H 81Br, D 35Cl?D 37Cl, and D 79Br?D 81Br. The measured rate constants are kHCl= (1.91±0.04) ×10−11, kHBr= (1.50±0.06) ×10−11, kDCl= (1.18±0.08) ×10−11, and kDBr= (8.34±0.17) ×10−12 cm3 molecule−1 sec−1. All of the processes are nearly resonant and the rates for the hydrogenated species are on the order of one‐tenth gas‐kinetic. The rates for DCl and DBr are found to be 1.6 and 1.8 times slower than the corresponding hydrogen halides. Direct comparison of the results with theoretical predictions for such resonant energy transfer processes shows disagreement, indicating that further development of theoretical methods for these systems is desirable.