The vibrational quantum number dependence of the collisional lifetime in nitric oxide selfrelaxation up to v'=25 A direct determination of the role of vibrationtovibration energy transfer in HF(v=3,4) selfrelaxation J. Chem. Phys. 84, 220 (1986); 10.1063/1.450174Vibrational relaxation of HF(v = 3, 4, 5) between 300 and 700 K The temperature dependencies of the total self-relaxation rate constants for the vibrational deactivation ofHF(v = 2) and HF(v = 1) and the state-to-state vibrationto-vibration (V-V) and vibration-to-translation-and-rotation (V-T,R) energy transfer components of the HF(v = 2) self-relaxation process are measured using the overtone vibration excitation-laser double resonance technique. The total self-relaxation rate constants vary inversely with temperature. The much weaker temperature dependence of HF(v = 2) self-relaxation compared to that of HF(v = I) arises from the significant role of the V-V energy transfer route. Competition between energetics and collision duration results in a weaker inverse variation with temperature for the slightly endothermic V-V route than for the exothermic V-T,R route for HF(v = 2).The branching ratio for V-V energy transfer increases slightly with temperature and the data suggest that two quantum relaxation processes constitute no more than 10% of the total self-relaxation of HF(v = 2). The available temperature dependence data on self-relaxation of HF(v = 1-5) form a consistent picture in which the energetics of the V-V and V-T,R relaxation pathways control their relative contributions to the total energy transfer.by direct overtone vibration excitation at -1.3 f.L. A fast ( -5 ns) InAs detector in conjunction with a transient 780
Overtone vibration-laser double resonance studies of HF(v = 2) yield self-relaxation rate constants for v = 2 and v = 1 of k2 = (19.8±1.0) ×10−12 cm3 molecule−1 s−1 and k1 = (1.46±0.1) ×10−12 cm3 molecule−1s−1, respectively. These experiments indicate that the fraction of HF(v = 2) molecules relaxing via vibration-to-vibration energy transfer is only 0.35±0.10, in sharp contrast to trajectory and scaling calculations which predict the dominance of this pathway over vibration-to-translation, rotation energy transfer.
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