VUV photochemistry of oriented molecules: methylchloride on highly oriented pyrolytic graphite

• Published in: Surface science 1997-11, Vol.390 (1), p.237-242
• Main Authors: Wilkes, J., Lamont, C.L.A., Sìller, L., Coquel, J.M., Palmer, R.E.
• Format: Article
• Language: English
• Subjects: Chemistry; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electron and ion emission by liquids and solids; impact phenomena; Exact sciences and technology; General and physical chemistry; Graphite; Halohydrocarbons; Impact phenomena (including electron spectra and sputtering); Methylchloride; Photochemistry; Photon stimulated desorption; Photon- and electron-stimulated desorption; Physical chemistry of induced reactions (with radiations, particles and ultrasonics); Physics; Surface phase transitions; Surface photochemistry
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/S0039-6028(97)00558-X

The photoionization of CH 3Cl adsorbed on highly oriented pyrolytic graphite has been investigated as a function of the photon energy in the range 13–35 eV. Two ions were detected — CH + 3 and H + — which show differences in their coverage and energy dependences. At very low coverages only H + ions are produced, while at higher coverages (still in the monolayer regime) CH + 3 ions are also observed, reflecting a change in the orientation of the molecule on the surface as a function of coverage. The cross-section curves as a function of the photon energy for both ions show a maximum at 22 eV, while the onsets are at 16 eV for CH + 3 and 19 eV for H +.