Temperature dependence of vibrational relaxation in the HF, DF, HF–CO2, and DF–CO2 systems

Abstract

The laser excited fluorescence method has been employed to determine rate constants for V -+ V, R and V -+ R, T relaxation HF(v = I) and DF(v = I) by CO 2 over the temperature range from 295 to 670°K. The self-deactivation rates for HF(v = I) and DF(v = I) by ground state molecules and the rate of V -+ V, R transfer from HF(~' = I) and DF(v = I) to the CO 2 (00 0 I) state exhibit a marked decrease with increasing temperature. The results provide additional evidence for the conversion of the large vibrational energy defects of the present systems into rotational motion of the hydrogen halide under the influence of a sizable attractive intermolecular potential well.

Long Range Collisional Energy Transfer from Highly Vibrationally Excited Pyrazine to CO Bath Molecules: Excitation of the v = 1 CO Vibrational Level

“…For example, scattering probabilities for energy transfer between CO 2 (00 0 1) and N 2 ( v = 1) are characterized by an inverse temperature dependence in which the excitation probability increases as the temperature decreases, a clear signature of long-range attractive-force energy-transfer processes. This behavior has been observed experimentally for a variety of systems in addition to CO 2 /N 2 , such as the deactivation of hydrogen halides with different bath molecules. − …”

“…This behavior has been observed experimentally for a variety of systems in addition to CO 2 /N 2 , such as the deactivation of hydrogen halides with different bath molecules. [20][21][22] The Sharma-Brau long-range, V-V energy-transfer model has also been applied successfully to the probability of scattering into the low rotational states (J ) 0-40) of the antisymmetric (00 0 1) stretch level of CO 2 after collisions with highly vibrationally excited pyrazine. 6 In contrast to this near-resonant energy-transfer process that characterizes the excitation of the low rotational states of CO 2 (00 0 1) by hot pyrazine, evidence for a slightly more repulsive-force energy-transfer mechanism was also observed for scattering into the higher rotational states (J > 41) of the CO 2 00 0 1 vibrational state.…”

Intermolecular V–V energy transfer in the photodissociation of CO2–HF(v=1)

“…Vibrational energy transfer between HF and CO 2 in full collisions has been studied in great detail [46][47][48][49][50][51][52][53][54] and it is instructive to compare these with the results of the present study. We begin by noting that numerous studies have shown that HF (vϭ1) relaxes collisionally with CO 2 via the V -V process discussed above, namely by coupling to the CO 2 (00 0 1) asymmetric stretching vibrational state.…”