Vibration-to-Vibration Energy Transfer in Hydrogen Bromide Mixtures

The laser-excited vibrational fluorescence technique has been used to determine the rate constants for vibration-to-vibration energy transfer from HBr to other molecules in gaseous mixtures. Cross sections at room temperature have been found: σHBr–N2 = (1.78 ± 0.17) × 10−2 Å2,σHBr–CO = (5.5 ± 0.3) × 10−2 Å2,σD2–HBr = (9.10 ± 0.96) × 10−3 Å2,σHBr–O2 ≤ (9.3 ± 0.6) × 10−4 Å2. The cross section for vibration-to-rotation or translation energy transfer between HBr and D2 has also been determined as σHBr–D2 = (0.96 ± 0.1) × 10−4 Å2. The dependence of cross section on V → V energy level differences is about the same magnitude as in the analogous HCl systems but considerably larger than it is in other diatomic—diatomic systems. Strong intermolecular forces and larger amplitudes of hydrogen atom stretching vibration are likely to be the dominant reason for the observed phenomena.