Approach to thermal equilibrium in atomic collisions

Journal Article

The energy relaxation of fast atoms moving in a thermal bath gas is explored experimentally and theoretically. Two time scales characterize the equilibration, one a short time, in which the isotropic energy distribution profile relaxes to a Maxwellian shape at some intermediate effective temperature, and the second, a longer time in which the relaxation preserves a Maxwellian distribution and its effective temperature decreases continuously to the bath gas temperature. The formation and preservation of a Maxwellian distribution does not depend on the projectile to bath gas atom mass ratio. This two-stage behavior arises due to the dominance of small angle scattering and small energy transfer in the collisions of neutral particles. Measurements of the evolving Doppler profiles of emission from excited initially energetic nitrogen atoms traversing bath gases of helium and argon confirm the theoretical predictions. © 2008 The American Physical Society.

Full Text

Duke Authors

Cited Authors

  • Zhang, P; Kharchenko, V; Dalgarno, A; Matsumi, Y; Nakayama, T; Takahashi, K

Published Date

  • March 11, 2008

Published In

Volume / Issue

  • 100 / 10

Electronic International Standard Serial Number (EISSN)

  • 1079-7114

International Standard Serial Number (ISSN)

  • 0031-9007

Digital Object Identifier (DOI)

  • 10.1103/PhysRevLett.100.103001

Citation Source

  • Scopus