Reaction and deactivation of HCl(v=1,2) by Cl, Br, and H atoms

Journal Article · Fri Aug 15 04:00:00 EDT 1980 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.440350· OSTI ID:5167208

Macdonald, R G; Moore, C B

Total decay rates for HCl(v=2, 1) were measured in the range 294--439 K for Cl, 295--390 K for Br, and at 296 K for H. HCl(v=2) was produced directly by pulsed laser excitation of the overtone. The fraction of HCl(v=2) relaxed to HCl(v=1) was determined. For HCl(v=2) + Cl, relaxation gave entirely HCl(v=1) within an experimental uncertainty of +- 10%, the total relaxation rate was large, k/v-barapprox. =5 A/sup 2/, and rates varied only slightly with temperature. For Br+HCl(v=2) reaction to HBr(v=0) + Cl is exoergic by about kT. Relaxation to HCl(v=1) is the dominant process. Reaction contributes roughly 17% and 34% to the loss of HCl(v=2) at 295 and 390 K, respectively. In contrast to the result for Br and for O(reported previously), H+HCl(v=2) gives 65% H/sub 2/+Cl and only 35% HCl(v=1)+H. For HCl(v=1)+H, Cl, O the vibrational excitation energy is greater than the activation energy for reaction. The relaxation rates are between 1/2 and 1/3 of the A values for the measured thermal exchange rates A exp(-..delta..E/sub act//RT). For HCl(v=1)+Br, well below threshold, the rate is some 20 times less than for HCl(v=1)+Cl. The rate for HCl(v=2)+Br, just above reaction threshold is not dramatically larger. The ratios of vibrational relaxation rates for HCl(v=2) vs HCl(v=1) are 5.0 +- 1.3, 4.2 +- 0.4, and 5.0 +- 1.3 for O, Cl, and Br, respectively. Any first order linear perturbation treatment gives rates proportional to v; the data scale more closely as v/sup 2/.

• Research Organization: Department of Chemistry, University of California and Materials and Molecular Research Division of the Lawrence Berkeley Laboratory, Berkeley, California 94720
• OSTI ID: 5167208
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 73:4; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ATOM COLLISIONS
ATOM-MOLECULE COLLISIONS
BROMINE
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHLORINE
COLLISIONS
CRYOGENIC FLUIDS
DE-EXCITATION
ELEMENTS
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
EXCITED STATES
FLUIDS
HALOGENS
HYDROCHLORIC ACID
HYDROGEN
HYDROGEN COMPOUNDS
INORGANIC ACIDS
KINETICS
MEDIUM TEMPERATURE
MOLECULE COLLISIONS
NONMETALS
REACTION KINETICS
RELAXATION
VIBRATIONAL STATES