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We have measured the absolute total cross sections for CH2SH⁺(CH3S⁺), CH2S⁺, HCS⁺, HS⁺, CH3⁺, and CH2⁺ produced by the collision-induced dissociation (CID) reaction of CH3SH⁺(1²A‘‘) + Ar in the center-of-mass collision energy range of 1−36 eV. While the onset for CH3⁺ is consistent with the thermochemical threshold for the formation of CH3⁺ + 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 CH2SH⁺ structure. The relative yields for CH2SH⁺, CH2S⁺, HCS⁺, HS⁺, CH3⁺, and CH2⁺ formed in the CID reaction, which strongly favor the C−S bond scission process leading to the formation of CH3⁺ + SH, are significantly different from those measured in previous photoionization and charge exchange studies. Since the CH3⁺ + SH channel is not among the most stable product channels, this observation suggests that the collision-activated dissociation of CH3SH⁺ is nonstatistical. The high yield for CH3⁺ + 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 CH3SH⁺, and to weak couplings between the low-frequency C−S and the high-frequency C−H stretching vibrational modes of CH3SH⁺. The differences in excitation mechanisms for CH3SH⁺ via collision activation, photoionization, and charge exchange are responsible for the different fragment ion distributions from CH3SH⁺ observed in these experiments.

We present here the assignment and simulation of rotational transitions for the H2+(X 2Σg+, v+=0, 2, 9 and 11) vibronic bands using the Buckingham–Orr–Sichel (BOS) model. The simulation shows that perturbation of PFI-PE rotational line intensities due to near-resonance autoionization decreases as v+increases. Experimental rotational constants for H2+(X 2Σg+, v+=0, 2, 9 and 11) are determined with higher accuracy than those obtained in previous HeI and NeI photoelectron studies. In agreement with previous experimental and theoretical investigations, only the ΔN=0 and ±2 rotational branches are observed in the PFI-PE spectrum for H2.