Vibrational energy transfer in near resonance due to dipole–dipole interactions

Abstract

The contribution of long-range forces to the observed rates of V 4 V energy transfer processes has been studied. The theoretical model uses the first order perturbation approximation to generate a probability function, with the dipoledipole perturbing potential as given by Margenau: Vir = [( 1/6)1/2pl.p2]R-3. The probability function derived is shown to be a strong function of the energy mismatch between the IR bands of the colliding molecules. The calculation emphasizes the importance of rotational state population effects, the most important J states being those which minimize tbe energy mismatch. A complete analysis of energy transfer between CO(u) and COS(OO0) where v = 1,2, . . . 13 is presented. The calculation reveals the importance of combination bands in the energy transfer mechanism of polyatomics. The temperature dependence for near-resonant processes is also studied and the importance of the V + R energy transfer leads to the classification of 00 (band-center energy mismatch) into three categories small, medium, and large, according to the temperature dependence that the corresponding processes exhibit. The predictions of the theoretical model are compared to experimental data for the same system.

Isotope effects in the quenching of electronically excited atoms. Quenching of I(52P½) by methane and deuteromethanes studied by time-resolved resonance fluorescence

“…The calculation employed here is similar in principle to that described by Lev-On et aZ. 26 and Gait 27 (following the work of Mahan 2 8 ) for resonant vibration-tovibration energy transfer. The first application of these ideas to E-VR transfer was by E ~i n g , ~~ but the approximations employed in that calculation only allowed order of magnitude comparison between theory and experiment.…”

Relaxation of DF(v = 1) by various polyatomic molecules

“…The close agreement of theoretical calculations and the DF-CH4 V-V rates strongly supports dipole-dipole interactions as the exchange mechanism and suggests that multiquantum rotational transitions, AJ > 1, play a significant role in reducing the energy defect of the exchange. Calculations similar to those of Lev-On and coworkers [17,20] would probably establish the temperature dependence of the nonresonant exchanges such as HF-CH,, DCl-CHa, and…”

Direct detection of nuclear scattering of sub-Gev dark matter using molecular excitations

“…For some molecules with permanent dipole moment (which are infrared active), this V − V energy exchange is due to the long-range dipole-dipole interaction between the colliding partners. Thus, applying first-order time dependent perturbation theory within the impact parameter approximation, it was shown in [82,149] that the probability of resonant quenching for the process AB(0,J 1 )+AB(v, J 2 )→AB(1, J 1 + ∆J 1 )+AB(v − 1, J 2 + ∆J 2 ), thermally averaged over J 1 (which is just J init for the specific case described in the body of this study) is given by…”

“…The approach of Lev-On et al [82,149] followed here accounts for the V −V energy transfer in self-relaxation of highly harmonic molecules. However, it does not include explicitly the role of rotational states and, more importantly, it does not include a V −T transfer pathway.…”