標題: Infrared absorption of methanethiol clusters (CH3SH)(n), n=2-5, recorded with a time-of-flight mass spectrometer using IR depletion and VUV ionization
作者: Fu, Lung
Han, Hui-Ling
Lee, Yuan-Pern
應用化學系
應用化學系分子科學碩博班
Department of Applied Chemistry
Institute of Molecular science
關鍵字: hydrogen bonds;infrared spectra;molecular clusters;molecular configurations;molecule-photon collisions;organic compounds;photoionisation;red shift;time of flight mass spectra
公開日期: 21-十二月-2012
摘要: We investigated IR spectra in the CH- and SH-stretching regions of size-selected methanethiol clusters, (CH3SH)(n) with n = 2-5, in a pulsed supersonic jet using infrared (IR)-vacuum ultraviolet (VUV) ionization. VUV emission at 132.50 nm served as the source of ionization in a time-of-flight mass spectrometer. Clusters were dissociated with light from a tunable IR laser before ionization. The variations in intensity of methanethiol cluster ions (CH3SH)(n)(+) were monitored as the IR laser light was tuned across the range 2470-3100 cm(-1). In the SH-stretching region, the spectrum of (CH3SH)(2) shows a weak band near 2601 cm(-1), red-shifted only 7 cm(-1) from that of the monomer. In contrast, all spectra of (CH3SH)(n), n = 3-5, show a broad band near 2567 cm(-1) with much greater intensity. In the CH-stretching region, absorption bands of (CH3SH)(2) are located near 2865, 2890, 2944, and 3010 cm(-1), red-shifted by 3-5 cm(-1) from those of CH3SH. These red shifts increase slightly for larger clusters and bands near 2856, 2884, 2938, and 3005 cm(-1) were observed for (CH3SH)(5). These spectral results indicate that the S-H center dot center dot center dot S hydrogen bond plays an important role in clusters with n = 3-5, but not in (CH3SH)(2), in agreement with theoretical predictions. The absence of a band near 2608 cm(-1) that corresponds to absorption of the non-hydrogen-bonded SH moiety and the large width of observed feature near 2567 cm(-1) indicate that the dominant stable structures of (CH3SH)(n), n = 3-5, have a cyclic hydrogen-bonded framework. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4770227]
URI: http://dx.doi.org/10.1063/1.4770227
http://hdl.handle.net/11536/21297
ISSN: 0021-9606
DOI: 10.1063/1.4770227
期刊: JOURNAL OF CHEMICAL PHYSICS
Volume: 137
Issue: 23
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