State-to-state dynamics of H+HX collisions. I. The H+HX. -->. H/sub 2/+X (X = Cl,Br,I) abstraction reactions at 1. 6 eV collision energy

Journal Article · Mon May 01 04:00:00 EDT 1989 · J. Chem. Phys.; (United States)

OSTI ID:6315187

Aker, P M; Germann, G J; Valentini, J J

The rotational and vibrational state distributions of the H/sub 2/ product from the reactions of translationally excited H atoms with HCl, HBr, and HI at 1.6 eV are probed by coherent anti-Stokes Raman scattering spectroscopy after only one collision of the fast H atom. Despite the high collision energy, only the very exoergic (..delta..H = -1.4 eV) hydrogen atom abstraction involving HI leads to appreciable H/sub 2/ product vibrational excitation. For this reaction the H/sub 2/ vibrational distribution is strongly inverted and peaks in v' = 1, with 25% of the total available energy partitioned to vibration. For the mildy exoergic (..delta..H = -0.72 eV) reaction with HBr and the nearly thermoneutral (..delta..H = -0.05 eV) reaction with HCl, very little energy appears in H/sub 2/ vibration, 9% and 2%, respectively, and the vibrational state distributions peak at v' = 0. However, in all three reactions a significant fraction, 18% to 21%, of the total energy available appears as H/sub 2/ rotation. All three reactions show a strong propensity to conserve the translational energy, that is the translational energy of the H/sub 2/+X products is very nearly the same as that of the H+HX reactants. For the reactions with HCl, HBr, and HI the average translational energy of the products is 1.3, 1.7, and 1.7 eV, respectively, and the width of the translational energy distribution is only about 0.5 eV full width at half maximum. The energy disposal in all three reactions is quite specific, despite the fact that this high collision energy is well above the barrier to reaction in all three systems and a large number of product quantum states are energetically accessible. Only a few of these energetically allowed final states are appreciably populated.

• Research Organization: Department of Chemistry, University of California, Irvine, California 92717
• OSTI ID: 6315187
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 90:9; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
640304* -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
ATOM COLLISIONS
ATOM-MOLECULE COLLISIONS
CHEMICAL REACTIONS
COLLISIONS
DISTRIBUTION
ELEMENTS
ENERGY LEVELS
ENERGY RANGE
ENERGY TRANSFER
ENERGY-LEVEL DENSITY
EV RANGE
EV RANGE 01-10
EXCITED STATES
HALOGEN COMPOUNDS
HYDRIODIC ACID
HYDROBROMIC ACID
HYDROCHLORIC ACID
HYDROGEN
HYDROGEN COMPOUNDS
INORGANIC ACIDS
IODINE COMPOUNDS
LASER SPECTROSCOPY
MOLECULE COLLISIONS
NONLINEAR OPTICS
NONMETALS
OPTICS
RAMAN SPECTROSCOPY
ROTATIONAL STATES
SPECTROSCOPY
VIBRATIONAL STATES