Accession Number:

ADA256342

Title:

Experimental and Theoretical Investigation of Surface Chemistry Induced by Direct and Indirect Electronic Excitation

Descriptive Note:

Final rept. Aug 1988-Jan 1992

Corporate Author:

NORTHWESTERN UNIV EVANSTON IL DEPT OF CHEMISTRY

Report Date:

1992-08-01

Pagination or Media Count:

66.0

Abstract:

A combined theoretical and experimental investigation of the photochemistry of methyl iodide on rutile at 100-110 K has been attempted in order to assess the importance of each of the possible direct or indirect photon absorption processes. We have used x-ray photoelectron spectroscopy XPS, temperature programmed desorption TPD and a UHV chamber designed for 257-351 nm laser irradiation of the adlayer followed by time-of-flight mass spectrometry TOF-MS. We have observed that following irradiation, methyl photofragments are ejected into the vacuum. These photofragments possess a characteristic translational energy distribution extending up to 1.9 eV in the case of 257 nm radiation, which varies somewhat with photodissociation wavelength and methyl iodide coverage. Two broad peaks are visible in the translational energy distribution corresponding to methyl fragments with energies of 1.1 and 0.03 eV. The higher energy fragments are produced with a relatively narrow angular distribution and some vibrational excitation in the vl and v2 umbrella modes of the methyl radical, whilst those of low translational energy are produced with a much broader angular distribution and almost no population in either of the v vibrational mode v1 and v2.

Subject Categories:

  • Organic Chemistry
  • Radiation and Nuclear Chemistry
  • Crystallography
  • Atomic and Molecular Physics and Spectroscopy

Distribution Statement:

APPROVED FOR PUBLIC RELEASE