QUANTUM-MECHANICAL AND SEMICLASSICAL STUDIES OF N-2 COLLISIONS AND THEIR APPLICATION TO THERMALIZATION OF FAST N ATOMS(N)

Energy loss of fast N(S-4) atoms in a bath gas of N-2 molecules is inv estigated taking into account elastic and inelastic collisions. Quantu m mechanical calculations using a vibrationally close-coupled rotation ally sudden approach are performed to obtain the elastic scattering cr oss sections. Inelastic cross sections involving re-vibrational transi tions of the molecules are determined from a quantum-classical approac h in which the vibrational motion of the molecule is treated by the ti me-dependent quantum mechanical method and the remaining degrees of fr eedom described by classical mechanics. The computed angular and energ y resolved cross sections are used to construct the Boltzmann kernel f or energy relaxation of fast N(4S) atoms from which the parameters gov erning the thermalization are readily extracted. (C) 1998 American Ins titute of Physics. [S0021-9606(98)01903-5].