Moment theory of electron thermalization in gases

Journal Article · Thu Jul 15 04:00:00 EDT 1982 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.443870· OSTI ID:5198111

Knierim, K D; Waldman, M; Mason, E A

A time-dependent moment method for solving the Boltzmann equation, not restricted to elastic collisions, is applied to the description of the thermalization of a beam of electrons in a gas. An exact solution is also obtained for diffusion and velocity relaxation by elastic collisions at very short times, before appreciable energy is lost. These results are compared with a recent approximate theory of Mozumder for electron thermalization, using two model systems: the Maxwell model (constant collisions frequency), and the rigid-sphere interaction (constant collision cross section). All results are exact for the Maxwell model, but for rigid-sphere interactions the errors in the velocity and energy relaxation times from Mozumder's method are approximately 25%. Many real systems are therefore probably described satisfactorily by the approximate theory, unless perhaps the cross sections have a peculiar energy dependence or inelastic collisions are important. If more accurate results are needed, the present moment method gives a systematic procedure for the calculation of higher-order approximations. Although the specific examples treated here consider only elastic collisions, the moment method applies to the case of inelastic collisions as well.

• Research Organization: Brown University, Providence, Rhode Island 02912
• OSTI ID: 5198111
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 77:2; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

640304* -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
ATOM COLLISIONS
BEAMS
CHARGED-PARTICLE TRANSPORT
COLLISIONS
CROSS SECTIONS
ELASTIC SCATTERING
ELECTRON BEAMS
ELECTRON COLLISIONS
ELECTRON-ATOM COLLISIONS
ELECTRON-MOLECULE COLLISIONS
ENERGY LOSSES
FLUIDS
GASES
LEPTON BEAMS
LOSSES
MOLECULE COLLISIONS
MOMENTS METHOD
PARTICLE BEAMS
RADIATION TRANSPORT
SCATTERING
SLOWING-DOWN
THERMALIZATION