Reactive scattering of O(1D)+HD: Product speed and angle distributions

Abstract

The reaction dynamics of O(1D)+HD → OH+D and OD+H was investigated at a collision energy of 4.55 kcal/mole in a crossed-beam apparatus. The speed and angle distributions of H(D) products were interrogated using Doppler-shift measurements in a (1+1) REMPI (resonantly enhanced multiphoton ionization) detection scheme. Both product channels exhibited marked forward–backward asymmetry in the angular distributions and the translational energy release to the OD+H channel was substantially larger, about 1.4 on the average, than that to the OH+D product.

Quantum mechanical calculation of product state distributions for the O(1D)+H2→OH+H reaction on the ground electronic state surface

“…23 Interest in the excited state effects in this reaction has arisen in the last few years as a result of several experiments. 10,12,14 At low collision energies all these experimental results point to the dominance of the insertion mechanism, proceeding over the ground PES, 1AЈ, and involving a very short lived collision complex. Experimental results at higher collision energies have been interpreted as pointing to the participation of a direct abstraction mechanism involving the excited 1AЉ and perhaps the 2AЈ PES.…”

“…Recent experiments 10,12,14 and theoretical calculations 17,22,23,25 give evidence that excited surface effects play some role ͑see however Ref. 18 for evidence that there may be aspects of the product state distributions which may be well explained by reaction only on the lowest potential energy surface͒.…”

“…There have been a large number of experimental studies of thermal rate coefficients, 2,3 product vibrational [4][5][6] and rotational [7][8][9] distributions, integral cross sections, 10 and angular and translational distributions. [11][12][13][14][15][16][17][18] Theoretical studies include both classical trajectory [19][20][21][22][23][24][25] as well as quantum mechanical calculations. [26][27][28][29][30][31][32] The interaction of electronically excited oxygen with hydrogen molecules…”

Dynamical studies and product analysis of O(1D) + H2/D2reactions

“…Using the potential energy surfaces of Murrell et al [26] (MC PES), Schinke and Lester [28] (SL PES) and Ho et al [17] (K or RKHS PES), Schatz et al [40] report that the average scattering angle is close to 1.57 rad (90 ). This is verified when several rotational periods occur before dissociation of the complex into products, but this symmetric angular distribution can also arise from collisions proceeding via insertion [41]. On the other hand, this reaction is believed to occur through an abstraction mechanism on the first excited surface [7,8].…”

Is there a barrier for the C2v insertion reaction in O(1D)+H2? A test dynamics study based on two-valued energy-switching potential energy surfaces

“…However, at higher energies, recent cross-molecular beam experiments by Che and Liu [35] and trajectory studies [1,23,26] suggest that it is likely that more than one reaction pathway is involved. We further observe that existence of a barrier for reaction is incompatible (at least at the classical level of dynamics) with a capture-type mechanism at low energies.…”