ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
High-sensitivity direct IR laser absorption methods are exploited to investigate quantum state-resolved reactive scattering dynamics of F+n-H2(j=0,1)→HF(v,J)+H in low-density crossed supersonic jets under single collision conditions. Nascent rotational state distributions and relative cross sections for reactive scattering into the energetically highest HF (v=3,J) vibrational manifold are obtained as a function of center-of-mass collision energies from Ecom=2.4 kcal/mole down to 0.3 kcal/mole. This energy range extends substantially below the theoretically predicted transition state barrier [Ebarrier(approximate)1.9 kcal/mole; K. Stark and H. Werner, J. Chem. Phys. 104, 6515 (1996)] for the lowest adiabatic F(2P3/2)+H2 potential energy surface, therefore preferentially enhancing nonadiabatic channels due to spin–orbit excited F*(2P1/2) (ΔEspin–orbit=1.15 kcal/mole) in the discharge source. The HF (v=3,J) cross sections decrease gradually from 2.4 kcal/mole down to the lowest energies investigated (Ecom(approximate)0.3 kcal/mole), in contrast with exact adiabatic quantum calculations that predict a rapid decrease below Ecom(approximate)1.9 kcal/mole and vanishing reaction probability by Ecom(approximate)0.7 kcal/mol. Further evidence for a nonadiabatic F*(2P1/2) reaction channel is provided by nascent rotational state distributions in HF (v=3,J), which are 〉2–3-fold hotter than predicted by purely adiabatic calculations. Most dramatically, the nascent product distributions reveal multiple HF (v=3,J) rovibrational states that would be energetically inaccessible from ground state F(2P3/2) atom reactions. These quantum state resolved reactive scattering studies provide the first evidence for finite nonadiabatic dynamics involving multiple potential energy surfaces in this well-studied "benchmark" F+H2 reaction system. © 1999 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.480182
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