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

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Abstract
The initial vibrational distributions in both energetically accessible channels of the reaction between O(1D) 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 1A″ and 3A″ surfaces of the HOCl 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 HCl is observed.