Probing the effect of the H{sub 2} rotational state in O({sup 1}D) + H{sub 2} {yields} OH + H : theoretical dynamics including nonadiabatic effects and a crossed molecular beam study.
Theoretical estimates of reactive cross sections for O({sup 1}D) + H{sub 2}(X,{nu} = 0j){yields}OH(X) + H({sup 2}S), with H{sub 2} rotational quantum numbers j = 0 and 1, are obtained for a range of collision energies, E{sub col}. Crossed molecular beam measurements are also used to infer the ratio, r{sub 1,0}, of the j = 1 and 0 cross sections at E{sub col} = 0.056 eV. The theory indicates that the 1 {sup 1}A{prime} potential surface is the most important one. However, the 2 {sup 1}A{prime} and 1 {sup 1}A{prime} surfaces can also contribute. Adiabatic dynamics on the 1 {sup 1}A{prime} surface, particularly at E{sub col} above its 0.1 eV barrier to reaction plays a role. The 2 {sup 1}A{prime} surface, while not correlating with ground electronic state products, can still lead to products via nonadiabatic interactions with the 1 {sup 1}A{prime} surface. Many quantum dynamics and quasiclassical classical trajectory calculations are carried out. Accurate, ab initio based potential energy surfaces are employed. Quantum cross sections are based on helicity decoupled wave packet calculations for several values of total angular momentum. Nonadiabatic wave packet and trajectory surface hopping calculations, where appropriate, are carried out. An interesting, subtle picture emerges regarding the energy dependence of r{sub 1,0}. The theoretical results indicate, somewhat surprisingly, that, for E{sub col}<0.1 eV,r{sub 1,0} can be less than unity owing to the anisotropy of the ground state potential. Electronically excited states and nonadiabatic effects contribute to the overall cross sections for E{sub col}>0.1 eV, but the full r{sub 1,0} is only weakly sensitive to excited states. Our experimentally inferred r{sub 1,0} at E{sub col} = 0.056 eV, 0.95{+-}0.02, is in quantitative agreement with our best calculation, which suggests that the effect of potential anisotropy is correctly described by theory. The relation between these results and previous experimental findings is discussed.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 942945
- Report Number(s):
- ANL/CHM/JA-36135; JCPSA6; TRN: US201002%%413
- Journal Information:
- J. Chem. Phys., Vol. 113, Issue 17 ; Nov. 1, 2000; ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- ENGLISH
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