Accession Number:

ADA250205

Title:

Gas-Surface Interactions Near Dissociation Threshold

Descriptive Note:

Final rept. Nov 1988-Oct 1991

Corporate Author:

UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES DEPT OF CHEMISTRY

Personal Author(s):

Report Date:

1992-03-26

Pagination or Media Count:

12.0

Abstract:

The main thrust of our program was directed towards the study collision-induced dissociation CID of hyperthermal molecules on insulators MgO, semiconductors GaAs and metals Ag. Supersonic beams of nitroso compounds entered the UHV chamber with kinetic energies variable between 0.5 and 7 eV. NO products were detected state-selectively using two-frequency laser ionization. CTD yields were measured as a function of surface temperature and incident kinetic energy, and complete energy deposition in the NO product was determined in each case. CID yields rise sharply with incident kinetic energy, with non-vanishing values even slightly below dissociation threshold at high surface temperature. The yield depends on the stiffness of the surface. The NO distributions are similar to those obtained in the gas-phase unimolecular decomposition of these molecules and indicate a broad distribution of internal energies. In the newest phase of this program, the photodissociation of C1NO adsorbed on a rough MgO surface is studied at 365 nm. The NO state distributions differ greatly from those obtained in gas-phase photodissociation and suggest that C1NO aggregates as islands on the surface and the NO and Cl undergo multiple collisions before desorption. Surface, Collision-Induced Dissociation, Photodissociation.

Subject Categories:

  • Physical Chemistry

Distribution Statement:

APPROVED FOR PUBLIC RELEASE