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Dissociation of CH<INF>3</INF>SH<SUP>+</SUP> by Collisional Activation: Evidence of Nonstatistical Behavior
- Source :
- The Journal of Physical Chemistry - Part A; September 4, 1997, Vol. 101 Issue: 36 p6513-6522, 10p
- Publication Year :
- 1997
-
Abstract
- We have measured the absolute total cross sections for CH<INF>2</INF>SH<SUP>+</SUP>(CH<INF>3</INF>S<SUP>+</SUP>), CH<INF>2</INF>S<SUP>+</SUP>, HCS<SUP>+</SUP>, HS<SUP>+</SUP>, CH<INF>3</INF><SUP>+</SUP>, and CH<INF>2</INF><SUP>+</SUP> produced by the collision-induced dissociation (CID) reaction of CH<INF>3</INF>SH<SUP>+</SUP>(1<SUP>2</SUP>A) + Ar in the center-of-mass collision energy range of 1−36 eV. While the onset for CH<INF>3</INF><SUP>+</SUP> is consistent with the thermochemical threshold for the formation of CH<INF>3</INF><SUP>+</SUP> + SH, the onsets for other product ions are higher than their corresponding thermochemical thresholds. Using a charge transfer probing technique, we conclude that the m/e = 47 amu ions observed in the CID reaction have mostly the CH<INF>2</INF>SH<SUP>+</SUP> structure. The relative yields for CH<INF>2</INF>SH<SUP>+</SUP>, CH<INF>2</INF>S<SUP>+</SUP>, HCS<SUP>+</SUP>, HS<SUP>+</SUP>, CH<INF>3</INF><SUP>+</SUP>, and CH<INF>2</INF><SUP>+</SUP> formed in the CID reaction, which strongly favor the C−S bond scission process leading to the formation of CH<INF>3</INF><SUP>+</SUP> + SH, are significantly different from those measured in previous photoionization and charge exchange studies. Since the CH<INF>3</INF><SUP>+</SUP> + SH channel is not among the most stable product channels, this observation suggests that the collision-activated dissociation of CH<INF>3</INF>SH<SUP>+</SUP> is nonstatistical. The high yield for CH<INF>3</INF><SUP>+</SUP> + SH observed in CID is attributed to the more efficient translational to vibrational energy transfer for the C−S stretch than for the C−H stretches of CH<INF>3</INF>SH<SUP>+</SUP>, and to weak couplings between the low-frequency C−S and the high-frequency C−H stretching vibrational modes of CH<INF>3</INF>SH<SUP>+</SUP>. The differences in excitation mechanisms for CH<INF>3</INF>SH<SUP>+</SUP> via collision activation, photoionization, and charge exchange are responsible for the different fragment ion distributions from CH<INF>3</INF>SH<SUP>+</SUP> observed in these experiments.
Details
- Language :
- English
- ISSN :
- 10895639 and 15205215
- Volume :
- 101
- Issue :
- 36
- Database :
- Supplemental Index
- Journal :
- The Journal of Physical Chemistry - Part A
- Publication Type :
- Periodical
- Accession number :
- ejs1122031