Nonequilibrium electron velocity distribution and temperature in thermalization of low-energy electrons in molecular hydrogen
The thermalization of low-energy electrons (epsilon< or approx. =0.1 eV) due to the rotational and elastic collisions in normal H/sub 2/ at the gas temperature T = 300 or 77 K is studied by the Monte Carlo simulation, where electrons are so diluted in molecules that the electron--electron collision is neglected as compared with the electron--molecule collision. The accuracy of the approximate theory based on the assumption of the local Maxwell velocity distribution (MD) is examined using, for simplicity, the rotational cross section of the Gerjuoy--Stein formula and the elastic cross section of the hard-sphere model, which are a little larger than the experimental cross sections at low electron energy (epsilon< or approx. =0.1 eV); the initial electron velocity distribution is taken to be the MD. The electron velocity distribution significantly deviates from the MD especially at low gas temperature (T = 77 K); consequently the degradation of the electron temperature T/sub e/ is slower than that for the MD and the thermalization time tau/sub th/ when T/sub e//T = 1.1 is larger than that for the MD to the extent of 20% at T = 300 K, where tau/sub th/ is dominated by the rotational collision, and 140% at T = 77 K, where tau/sub th/ is dominated by the elastic collision. tau/sub th/papprox. =1.9 ..mu..s Torr at T = 300 K, where p is the gas pressure, is about 27% larger than the experimental value of 1.5 ..mu..s Torr at T = 296 K for the higher initial electron energy (epsilonapprox.1 eV).
- Research Organization:
- National Aerospace Laboratory, Jindaiji-Machi, Chofu, Tokyo, Japan
- OSTI ID:
- 5693110
- Journal Information:
- J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 79:7; ISSN JCPSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
COLLISIONS
DISTRIBUTION
ELASTIC SCATTERING
ELECTRON COLLISIONS
ELECTRON-MOLECULE COLLISIONS
ELEMENTS
ENERGY LEVELS
ENERGY TRANSFER
EXCITED STATES
HYDROGEN
LOW TEMPERATURE
MEDIUM TEMPERATURE
MOLECULE COLLISIONS
MONTE CARLO METHOD
NONMETALS
ROTATIONAL STATES
SCATTERING
SLOWING-DOWN
THERMALIZATION
VELOCITY