MECHANISMS AND RATE CONSTANTS FOR THE VIBRATIONAL-RELAXATION OF HD(UPSILON = 4, 5, AND 6) IN COLLISIONS WITH HD, HE-4 AND D2
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abstract
The relaxation of highly vibrationally excited HD with several collision partners is examined using direct overtone excitation and time-resolved photoacoustic detection of the subsequent change in translational energy of the gas. Analysis of such data for HD(v=4, 5 and 6) self-relaxation yields vibration-translation (V-T) and vibrationvibration (VV) rate constants for collisions between HD(v=1 to 6) and HD(v=0). The V-T rate constant becomes larger than the VV rate constant above v=4. Similarly, relaxation data for the HD(v=4 and 5)4He systems is analyzed and the HD4He V-T rate constants at v=4 and v=5 are presented. The differences in the quantum number scaling of the V-T rates for the HDHD and HD4He systems are discussed. Finally, the time-resolved photoacoustic data for HD(v=4) relaxing in collisions with D2 shows the effect of the rapid, near-resonant VV energy transfer between HD in the v=1 through v=4 levels and D2 in v=0.
