Direct measurement of rotational energy transfer rate constants for H/sup 35/Cl (v = 1)

Journal Article · Sun Nov 01 04:00:00 EST 1987 · J. Chem. Phys.; (United States)

OSTI ID:6117391

Rohlfing, E A; Chandler, D W; Parker, D H

We investigate the rotational energy transfer of H/sup 35/Cl (v = 1) in collisions with thermal HCl at 298 K. Rotationally state-selective excitation of v = 1 over J = 1--6 is achieved by stimulated Raman pumping, and the rotational relaxation from the initially pumped level is monitored via 2+1 resonantly enhanced multiphoton ionization (REMPI) through the E /sup 1/..sigma../sup +/--X /sup 1/..sigma../sup +/0--1 band. The ions are detected in a time-of-flight mass spectrometer in order to ensure that only relaxation of H/sup 35/Cl is observed. We present empirical correction factors for determining relative rotational populations from the REMPI spectral line intensities and extract the rate constants for rotational energy transfer from the time-dependent populations using numerical techniques. The excellent sensitivity of the REMPI technique makes it possible to monitor the relaxation on very short collisional time scales (<0.1 hard sphere collision) and thereby enables us to determine the rate constants for both single quantum and multiquanta rotational transitions directly, without the use of a simplifying model for the matrix of rate constants. The measured rate constants illustrate the importance of multiquanta transitions for HCl; such transitions account for --30% of the total population loss from a given rotational level. We compare our rate constants to those obtained in previous measurements on HCl (v = 1) and HF (v = 2). We find that the rate constants are not adequately described by models based solely on the rotational energy defect of the vibrationally excited molecule.

• Research Organization: Combustion Research Facility, Sandia National Laboratories, Livermore, California 94550
• OSTI ID: 6117391
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 87:9; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

640304* -- Atomic
Molecular &amp; Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
COLLISIONS
ENERGY LEVELS
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
EXCITATION
EXCITED STATES
HYDROCHLORIC ACID
HYDROGEN COMPOUNDS
INORGANIC ACIDS
IONIZATION
KINETICS
MOLECULE COLLISIONS
MOLECULE-MOLECULE COLLISIONS
MONITORING
MULTI-PHOTON PROCESSES
PHOTOIONIZATION
ROTATIONAL STATES