THE $\tilde{A}^{2}\Pi_{u} -\tilde{X}^{2}\Pi_{g}$ TRANSITION OF ${CS_{2}}^{+}$ IN SOLID Ne: NEW ASSIGNMENT OF SOME VIBRONIC LINES

1. V. E. Bondybey, J. H. English, and T. A. Miller, J. Chem. Phys. 70, 1621 (1979). 2. V. E. Bondybey and J. H. English, J. Chem. Phys. 73, 3098 (1980). 3. M. Brommer and P. Rosumus, Chem. Phys. Lett. 206, 540 (1993).Author Institution: National Tsing Hua University, Hsinchu, Taiwan 30043.The $\tilde{A}^{2}\Pi_{u} -\tilde{X}^{2}\Pi_{g}$ system of ${CS_{2}}^{+}$ isolated in solid Ne was investigated by laser-induced fluorescence. Dispersed fluorescence spectrum in the range 475-570 nm and fluorescence excitation spectrum in the range 410-480 nm showed distinct vibrational progressions. Previous $studies^{1,2}$ reported irregular vibrational spacings for the $\tilde{A}$ and $\tilde{X}$ states due to Fermi resonance. We have carefully determined the line positions of the $\tilde{A} -\tilde{X}$ system of $^{12}C^{32}S_{2}{^{+}}, ^{13}C^{32}S_{2}^{+}$, and $^{12}C^{34}{S_{2}}^{+}$. By comparison of $^{13}C$-isotopic shifts relative to $^{34}S$-isotopic shifts for the corresponding lines, we were able to assign each component of the Fermi polyad. Our new assignments for the $\tilde{X}$ state are different from previous ones, for example: the (1,2,0) and (2,0,0) are interchanged, and the (1,4,0) and (3,0,0) are also interchanged; these new assignments agree with recent theoretical $calculations^{3}$. Similarly, we also propose new assignments for the vibronic lines of the $\tilde{A}$ state