Vib--rotational energy distributions and relaxation processes in pulsed HF chemical lasers

Journal Article · Wed Sep 01 04:00:00 EDT 1976 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.433316· OSTI ID:7345267

Ben-Shaul, A; Kompa, K L; Schmailzl, U

The rate equations governing the temporal evolution of photon densities and level populations in pulsed F+H/sub 2/..-->..HF+H chemical lasers are solved for different initial conditions. The rate equations are solved simultaneously for all relevant vibrational--rotational levels and vibrational--rotational P-branch transitions. Rotational equilibrium is not assumed. Approximate expressions for the detailed state-to-state rate constants corresponding to the various energy transfer processes (V--V, V--R,T, R--R,T) coupling the vib--rotational levels are formulated on the basis of experimental data, approximate theories, and qualitative considerations. The main findings are as follows: At low pressures, R--T transfer cannot compete with the stimulated emission, and the laser output largely reflects the nonequilibrium energy distribution in the pumping reaction. The various transitions reach threshold and decay almost independently and simultaneous lasing on several lines takes place. When a buffer gas is added in excess to the reacting mixture, the enhanced rotational relaxation leads to nearly single-line operation and to the J shift in lasing. Laser efficiency is higher at high inert gas pressures owing to a better extraction of the internal energy from partially inverted populations. V--V exchange enhances lasing from upper vibrational levels but reduces the total pulse intensity. V--R,T processes reduce the efficiency but do not substantially modify the spectral output distribution. The photon yield ranges between 0.4 and 1.4 photons/HF molecule depending on the initial conditions. Comparison with experimental data, when available, is fair. (AIP)

• Research Organization: Department of Chemical Physics, The Weizmann Institute of Science, Rehovot, Israel
• OSTI ID: 7345267
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 65:5; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
430300* -- Particle Accelerators-- Auxiliaries & Components
CHEMICAL LASERS
CHEMICAL REACTION KINETICS
EFFICIENCY
ENERGY LEVELS
ENERGY TRANSFER
EXCITED STATES
HYDROFLUORIC ACID
HYDROGEN COMPOUNDS
INORGANIC ACIDS
KINETICS
LASERS
OPERATION
REACTION KINETICS
RELAXATION
ROTATIONAL STATES
VIBRATIONAL STATES