Vibrational relaxation in H/sub 2/ molecules by wall collisions: Applications to negative ion source processes

Journal Article · Wed May 01 04:00:00 EDT 1985 · J. Vac. Sci. Technol., A; (United States)

DOI:https://doi.org/10.1116/1.573068· OSTI ID:5738760

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 from 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 deexcitation and reexcitation of vibrationally excited H/sub 2/ molecules undergoing repeated wall collisions. The initial 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 deexcitation 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--100 eV) a substantial fraction of the molecules survives 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 will be discussed.

• Research Organization: Lawrence Livermore National Laboratory, Livermore, California 94550
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5738760
• Journal Information: J. Vac. Sci. Technol., A; (United States), Journal Name: J. Vac. Sci. Technol., A; (United States) Vol. 3:3; ISSN JVTAD
• Country of Publication: United States
• Language: English

Related Subjects

640301* -- Atomic
Molecular & Chemical Physics-- Beams & their Reactions
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATOM COLLISIONS
COLLISIONS
COMPUTERIZED SIMULATION
ELECTRIC DISCHARGES
ELEMENTS
ENERGY LEVELS
ENERGY-LEVEL DENSITY
ENERGY-LEVEL TRANSITIONS
EXCITATION
EXCITED STATES
HYDROGEN
ION COLLISIONS
ION SOURCES
MOLECULE COLLISIONS
NONMETALS
RELAXATION
SIMULATION
VIBRATIONAL STATES
WALLS