Adsorption and photon-stimulated desorption of CCl 4 on an Al(111) surface investigated with synchrotron radiation

Jin Ming Chen*, Ru Gun Liu, Yao Jane Hsu, Su Chien Yang, Yuen Chung Liu, Yuan-Pern Lee, Ching Rong Wen, T. J. Chuang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

Adsorption and desorption of CCl 4 molecules on an Al(111) surface at 90 K are characterized with photoemission spectroscopy (PES) and photon-stimulated ion desorption (PSID) techniques following valence-level and core-level excitations. Results of valence-level and Cl(2p) core-level PES spectra indicate that CCl 4 dissociates partially upon adsorption on an Al(111) surface at submonolayer coverage and that molecular CCl 4 adsorbs to form multilayers at large exposures. The dissociation upon adsorption of CCl 4 on an Al surface at 90 K is likely mediated by the charge-transfer process. The Cl + desorption threshold at ∼18.5 eV in valence-level PSID spectra may originate from the 5t 2 →7a 1 * (C-Cl antibonding orbital) transition consistent with the Menzel-Gomer-Redhead (MGR) mechanism. The total-electron yield (TEY) spectrum and the Cl + PSID spectrum of solid CCl 4 following the Cl L-edge excitation are clearly dissimilar. The enhanced desorption yield of Cl + ions is detected at the Cl2p→7a 1 * excitation, compared to the Cl2p→8t 2 * and Cl2p→Rydberg state excitations. Cl(2p) core-level excitations yield much greater desorption of ions compared with direct valence-band excitation. Based on resonant photoemission spectra, core resonant excitations decay predominantly via spectator Auger transitions, whereas shape resonance excitation is followed by normal Auger decay. Enhanced Cl + ion desorption from solid CCl 4 following Cl2p→7a 1 * excitation is interpreted in terms of the rapid desorption via a repulsive surface which is directly related to spectator electrons localized in antibonding orbitals.

Original languageEnglish
Pages (from-to)8027-8035
Number of pages9
JournalJournal of Chemical Physics
Volume109
Issue number18
DOIs
StatePublished - 8 Nov 1998

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