Vibrational excitation of deuterium fluoride and hydrogen fluoride by atomic and diatomic species

Abstract

The vibrational excitation of H F and DF and the energy transfer efficiencies for various collision partners were investigated over the temperature and pressure ranges of 1400°K to 4100°K and 0.1 to 0.3 atm, respectively. The extent of excitation was determined as a function of time by continuously monitoring the infrared emission intensity at the center of the 1-0 vibration-rotation band of the molecule. Collisional efficiencies of HF, NB, 02, F, C1, and DF in relaxing H F and of DF, HF, and Nf in relaxing DF are reported. A comparison with relaxation data for pure H F taken at lower temperature suggests that long-range attractive forces are mechanistically of major importance in the relaxation process. The relatively high efficiency of atomic chlorine in relaxing HF, i.e., (TP)HF-HF/ ( T P ) H F -c~ 2 5 at 3000°K is discussed in terms of our previous result for atomic fluorine, i.e., (TP)HF-HF/(TP)HF-F = 18.

IR-laser-induced collisional pumping of small molecules. I. General discussion and experimental results for hydrogen fluoride

“…At maximum intensity the pulse contains 2.5 x 1020 photons cm-2, which means that, for example, a high excitation of a volume of 1 cm3 at a pressure of several tens of Torrs is not limited by the energy content of the laser pulse. The collisional cross-section UHF-HF is 5 11 k ' (Blauer et al 1972) leading to a gas kinetic collision time of ~~~l l = 3 5 ns at P H F = 50 Torr and T= 293 K. As even for the lower vibrational levels the crosssection for V-V exchange is of the order of the gas kinetic cross-section (Osgood et a1 1974), the requirement that V-V relaxation should be fast compared to the pulse duration is fulfilled in this pressure range. V-Trelaxation of the lower levels is lower by two orders of magnitude (Cohen and Bote 1976) so that the redistribution of vibrational energy is fast compared to V-T losses.…”

Quantum Dynamics of Rotational Energy Transfer Processes for N2–HF and N2–DF Systems

“…The rate coefficients for vibration–vibration (V–V) energy transfer processes N 2 (ν 1 = 0) + HF (ν 2 ) → N 2 (ν 1 ′ = 1) + HF (ν 2 ′ = ν 2 – 1) were measured by several research groups, where ν 1 and ν 2 are the vibrational quantum numbers of N 2 and HF/DF, respectively. ν 2 ranges from 1 to 7 for HF − and from 1 to 5 for DF. ,,− In particular, Yang et al showed the importance of near energy resonant vibration–rotation (V–R) channels in the relaxation processes of vibrationally excited HF by N 2 . These experimental data indicated that the vibrational energy transfer rate coefficients (∼10 –15 cm 3 s –1 mol –1 ) are much smaller than those of other systems in which the HF molecule participates, such as H 2 –HF (∼10 –12 cm 3 s –1 mol –1 ), H 2 O–HF (∼10 –10 cm 3 s –1 mol –1 ), ,, and HF–HF (∼10 –11 cm 3 s –1 mol –1 ) .…”

Monte Carlo calculations of reaction rates and energy distributions among reaction products. Reactions of HF and DF with H and D-atoms

“…Also, no theoretical rate data are available on the exchange reactions of HF+ D, DF+ H, and DF + D. Moreover, there are no theoretical rate coefficients for the deactivation of HF or DF by H and D-atoms, including contributions from both reactive and nonreactive collisions, except for the recent theoretical results reported by Wilkins [2] for the reactions of H-atoms with vibrationally excited HF molecules. Studies have been made of the (V->T, R) relaxation of HF by F [4][5][6][7][8][9][10], DF by F [4,[11][12][13], HF by HF [6,10,[14][15][16][17][18] and DF by DF [11,18,19].…”