Experimental and Theoretical Investigation of Surface Chemistry Induced by Direct and Indirect Electronic Excitation
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 v'=l and v'=2 '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 v'=1 and v'=2.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1992
- Accession Number
- ADA256342
Entities
People
- Eric Weitz
- Peter C. Stair
- S. J. Garrett
Organizations
- Northwestern University