Vibrational relaxation in H/sub 2/ molecules by wall collisions: applications to negative ion source processes. Revision 1

Conference · Fri Jan 18 04:00:00 EST 1985

OSTI ID:6106924

Karo, A M; Hiskes, J R; Hardy, R J

In the volume of a hydrogen discharge, H/sub 2/ molecules, excited to high vibrational levels (v'' > 6), are formed either by fast-electron collisions or form H/sup +//sub 2/ ions that are accelerated across the discharge-wall potential that undergo Auger neutralization prior to impact with the discharge chamber wall. We have used computer molecular dynamics to study the de-excitation and re-excitation of vibrationally-excited H/sub 2/ molecules undergoing repeated wall collisions. The translational energies range from thermal to 100 eV and the initial vibrational states range from v'' = 2 to v'' = 12. The average loss or gain of vibrational, rotational, translational, and total molecular energies and the survival rates of the molecules have been evaluated. At thermal energies vibrational de-excitation is the predominant process, and a consistent picture emerges of rapid energy redistribution into all the molecular degrees of freedom and a slower rate of loss of total molecular energy to the wall. At higher translational energies (1 to 100 eV) a substantial fraction of the molecules survive with large (v'' > 6) vibrational energy. This vibrational population provides a contribution to the total excited vibrational population comparable to that from the fast-electron collision process. Implications of these results for negative ion generation are discussed.

• Research Organization: Lawrence Livermore National Lab., CA (USA)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 6106924
• Report Number(s): UCRL-90943-Rev.1; CONF-841218-23; ON: DE85007229
• Country of Publication: United States
• Language: English

Related Subjects

640304* -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
ELEMENTS
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
EXCITATION
EXCITED STATES
HYDROGEN
NONMETALS
VIBRATIONAL STATES