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/<0.002/<0.002 (the values for 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.