A study of the high Rydberg state and ion–molecule reactions of carbon disulfide using the molecular beam photoionization method

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Abstract
The internal energy effects and the energetics of the ion/molecule reaction of carbon disulfide CS+2⋅⋅⋅CS2→CS+3+CS, S+2+2CS, C2S+3+S, and CS+4+C have been investigated in detail by photoionization of the neutral van der Waals carbon disulfide dimer. Using the relative Franck–Condon factors obtained by photoelectron spectroscopy, the relative reaction probabilities for the formation of various product channels of the above reactions with CS2+ in the ? 2Σu+ and ? 2Σg+ states were derived from the analysis of the photoionization efficiency (PIE) data for CS+3, S+2, C2S+3, and CS+4. From the measured threshold energies for CS+3, C2S+3, and CS+4, the heat of formation at 0 K for CS+3, C2S+3, and CS+4 are deduced to be 291.7±1.7, 318±3, and 246±6 kcal/mol, respectively. By comparing the peak heights of the autoionization resonances in the PIE curves for CS+3, S+2, and C2S+3, and normalizing these to the known absorption cross sections of the corresponding Rydberg levels for CS2, the relative reaction probabilities for the formation of various product channels of the chemi‐ionization processes CS*2(V,n)⋅⋅⋅CS2→CS+3+CS+e, C2S+3+S+e, S+2+2CS+e, and (CS2)+2+e as a function of Rydberg level (n) were determined. The branching ratios of these product channels for the reactions of CS*2(V, n=4 or 5) with CS2 were also measured. This experiment has demonstrated that molecular beam photoionization studies of van der Waals dimers is an excellent method for the quantitative study of the chemistry of excited molecules, especially for molecules in short‐lived radiative states.