[1 + 1] photodissociation of ${\rm CS}_{\rm 2}^ + (\tilde X{}^{\rm 2}\Pi _g)$ CS 2 + ( X ̃ 2 Π g ) via the vibrationally mediated $\tilde B^{\rm 2} \Sigma _u^ +$ B ̃ 2 Σ u + state: Multichannels exhibiting and mode specific dynamics

• Published in: The Journal of chemical physics 2011-03, Vol.134 (11), p.114309-114309-7
• Main Authors: Li, Jialin, Zhang, Cuimei, Zhang, Qun, Chen, Yang, Huang, Cunshun, Yang, Xueming
• Format: Article
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.3567071

Dissociation dynamics of ${\rm CS}_{\rm 2}^ +$ CS 2 + vibrationally mediated via its $\tilde B{}^2\Sigma _u^ +$ B ̃ 2 Σ u + state, was studied using the time-sliced velocity map imaging technique. The parent ${\rm CS}_{\rm 2}^ +$ CS 2 + cation was prepared in its $\tilde X{}^2\Pi _g$ X ̃ 2 Π g ground state through a [3 + 1] resonance enhanced multiphoton ionization process, via the 4 p σ 3 Π u intermediate Rydberg state of neutral CS 2 molecule at 483.14 nm. ${\rm CS}_{\rm 2}^ +$ CS 2 + ( $\tilde X{}^2\Pi _g$ X ̃ 2 Π g ) was dissociated by a [1+1] photoexcitation mediated via the vibrationally selected $\tilde B$ B ̃ state over a wavelength range of 267-283 nm. At these wavelengths the $\tilde C{}^2\Sigma _g^ +$ C ̃ 2 Σ g + and $\tilde D{}^2\Sigma _u^ +$ D ̃ 2 Σ u + states are excited, followed by numerous S + and CS + dissociation channels. The S + channels specified as three distinct regions were shown with vibrationally resolved structures, in contrast to the less-resolved structures being presented in the CS + channels. The average translational energy releases were obtained, and the S + /CS + branching ratios with mode specificity were measured. Two types of dissociation mechanisms are proposed. One mechanism is the direct coupling of the $\tilde C$ C ̃ and $\tilde D$ D ̃ states with the repulsive satellite states leading to the fast photofragmentation. The other mechanism is the internal conversion of the $\tilde C$ C ̃ and $\tilde D$ D ̃ states to the $\tilde B$ B ̃ state, followed by the slow fragmentation occurred via the coupling with the repulsive satellite states.