Nascent Vibrational Energy Distribution of CS(X1Σ+) Generated in the S(1D) + CS2 Reaction

The internal energy distributions of reaction products are important information in clarifying the mechanism of chemical reactions. There are few reports of the nascent vibrational energy distribution of CS(X1Σ+) generated in the S(1D) + CS2 reaction. As long as S(1D) is produced by photodissociation of CS2, CS(X1Σ+), as a product of the chemical reaction and as a photoproduct of CS2 is indistinguishable. In this study, S(1D) was generated by the photolysis of OCS at 248 nm, where CS2 hardly dissociates, and CS(X1Σ+) was generated only by the S(1D) + CS2 reaction. The vibrational levels v″ = 0–6 of CS(X1Σ+) were detected with laser-induced fluorescence (LIF) via the A1Π–X1Σ+ transition. The identical time profiles of the LIF intensities showed that all the vibrational levels were produced by the S(1D) + CS2 reaction. The relative nascent vibrational populations of CS(X1Σ+) determined from the area intensities of the excitation spectra are 1.00 ± 0.11/0.58 ± 0.06/0.31 ± 0.03/0.078 ± 0.009/0.013 ± 0.001/v″ = 5 and 6 are the upper limits) for v″ = 0/1/2/3/4/5/6. The distribution agrees well with the statistical (prior) distribution.