Dynamics of the O(3P) + CS2(XΣg+) → SO(X3Σ-) + CS(X1Σ+) Reaction

Abstract

The rovibrational state distributions of both the CS and the SO products following the reaction of O(3P) + CS2 have been investigated. The O(3P) atoms are generated by photolysis of NO2 using a frequency-tripled Nd:YAG laser at 355 nm. The SO(X3Σ-, v‘ ‘ = 0−6) and CS(X1Σ+, v‘ ‘ = 0−3) are observed directly using laser induced fluorescence (LIF) spectroscopy on the (B3Σ- − X3Σ-) and (A1Π − X1Σ+) transitions, respectively. The SO(X3Σ-) product is found to be highly excited with the vibrational state distribution inverted at v‘ ‘ = 1 and detectable population up to v‘ ‘ = 6, while the CS(X1Σ+) product vibrational state distribution is characterized as Boltzmann with a vibrational temperature of 1230 ± 155 K. The total vibrational excitation of both products accounts for 21% of the available energy to the products. The near nascent SO(X3Σ-, v‘ ‘ = 0−4) rotational state distributions are characterized by rotational temperatures in the range of 882−1312 K, and the near nascent CS(X3Σ+, v‘ ‘ = 0) is characterized by a temperature of 2986 ± 607 K. The total rotational energy of the products accounts for 34.8% of the available energy. Correlated ab initio calculations of the reaction pathway have been performed, resulting in accurate energies for the reactants, products, intermediates, and transition states. Optimized geometries for the intermediates and transition states have been obtained. The inverted vibrational state distribution of the SO(X3Σ-) product and the excited rotational state distribution of the CS(X1Σ+) product suggest a short-lived, nonlinear intermediate structure as the primary pathway for the reaction. The results from the ab initio calculations corroborate this model.