The interaction of O(1D2) with HCl: The initial vibrational distributions in the OH(2Π) produced by chemical reaction, and the HCl(1Σ+) produced by E–V energy transfer

Abstract

Enhancement of chargetransfer reaction rate constants by vibrational excitation at kinetic energies below 1 eV J. Chem. Phys. 79, 265 (1983); 10.1063/1.445566Rotational and vibrational energy distributions of 16OH(X 2Π) and 18OH(X 2Π) produced in the reaction of O(1 D) with H2O and H2 18OThe initial vibrational distributions in both energetically accessible channels of the reaction between O( ID) atoms and HCl molecules are reported. The measurements were made using very fast time-resolved Fourier transform spectroscopy to observe the emission spectra of the products before their vibrational populations could be altered by collisional relaxation. Both the OH from the reaction and the HCl created in the E-V energy transfer process have strongly inverted vibrational distributions. The cross section of the former is found to be about 20 times larger than that of the latter. Although spin forbidden, the E-V process is fast, due to the fact that the IA " and 3 A " surfaces of the HOCI intermediate are nearly energetically degenerate over a large region of configuration space. The results suggest that the dynamics of the interaction are dominated by the relatively slow O-Cl collision. The rapid motion of the H atom, in response to changes in the potential created by the motion of the heavier atoms, permits the system to sample the singlet-triplet intersection many times during the collision. OH rotational deactivation is very fast in this system; the average probability for rotational energy transfer in the v' = 3 level is more than four times larger than the gas kinetic collision probability. The time evolution of both vibrational distributions is also reported, and fast v-v energy transfer from vibrationally excited OH to ground state HCI is observed.

The dynamics of the reaction of O(1D) with HBr studied by crossed molecular beams and time-resolved Fourier transform spectroscopy

“…We believe, however, that these are not the true initial rotational distributions, because rapid rotational energy transfer had probably modified the rotational populations substantially, even at the time of the first spectrum (which corresponds to five gas kinetic collisions). Based on the behaviour we have observed (14,45,46) in other experiments involving vibrationally excited OH in collisions with molecules like O3 and HCl, we estimate that the OH rotational degree of freedom would be partially thermalized after five gas kinetic collisions, and completely thermalized at the second observation, which corresponds to about fifteen collisions.…”

“…HCl have been reported (12)(13)(14)(15). The reactions O( P, 'D) + HCl have also received significant theoretical attention (16a-c).…”

Quantum dynamical study of the O(D1)+HCl reaction employing three electronic state potential energy surfaces

“…The reaction of electronically excited oxygen with hydrochloric acid has been a focus of several experimental [1][2][3][4][5][6][7][8][9] and theoretical studies. The reaction plays an important role in the modeling of atmospheric chemistry and presents an interesting system for the study of fundamental dynamics.…”

Time-dependent wavepacket study for O(1D)+HCl (v0=0, j0=0) reaction

“…Based on these facts, we think the BLRS PES is probably reasonable for the part of an incoming channel of reaction (1). The fact that there is good agreement for the OH vibrational distribution between approximate quantal results17,18 and experiments1,10 also indicates that the BLRS PES is probably reasonable for the part of an outgoing channel of reaction (1a).…”

“…All these rate constant results are in close agreement with each other. Several experiments also determined qualitatively4,6 and quantitatively2,5,7,8 that reaction (1a) is predominant among the three competing pathways of reaction (1). In addition to kinetic studies, Luntz9 made the Ðrst attempt to investigate the dynamics of the title reaction.…”