Ion core structure in(CS 2 ) n + and(CS 2 ) n − (n=3–10) studied by infrared photodissociation spectroscopy

Infrared photodissociation spectra of (CS2)n+ and(CS2)n− with n=3–10 are measured in the 1100–2000 cm−1 region. All the (CS2)n+ clusters exhibit three bands at ∼1410, ∼1490, and ∼1540 cm−1. The intensity of the1540 cm−1 band relative to those of the other bands increases with increasing the cluster size, indicating that the band at 1540 cm−1 is assignable to the antisymmetric CS stretching vibration of solvent CS2 molecules in the clusters. On the basis of density functional theory calculations, the 1410 and 1490 cm−1 bands of (CS2)n+ are assigned to CS stretching vibrations of the C 2S4+ cation core with a C2 form. The (CS2)n− clusters show two bands at around 1215 and 1530 cm−1. Similar to the case of cation clusters, the latter band is ascribed to the antisymmetric CS stretching vibration of solvent CS2 molecules. Vibrational frequency analysis of CS2− and C2S4− suggests that the 1215 cm−1 band is attributed to the antisymmetric CS stretching vibration of the CS2− anion core with a C2v structure.