à 2 Π u state-intermediated two-photon dissociation of CS2+ via the first channel

The [1+1] à 2Πu-state resonance enhanced two-photon dissociation process of CS2+ molecular ions has been investigated by measuring the photofragment S+ excitation (PHOFEX) spectrum in the wavelength range of 424–482 nm, where the CS2+ molecular ions were prepared purely by [3+1] multiphoton ionization of the neutral CS2 molecules at 483.2 nm. The PHOFEX spectrum was assigned essentially to the CS2+(à 2Πu)←CS2+(X̃ 2Πg) transition, and the dissociation mechanism of CS2+ was preliminarily attributed to (i) CS2+(X̃ 2Πg)→CS2+(à 2Πu) through one-photon excitation, (ii) CS2+(à 2Πu)→CS2+(X̃†) via internal conversion process due to the vibronic coupling between the à and X̃ states, (iii) CS2+(X̃†)→CS2+(B̃ 2Σu+) through the second photon excitation, and (iv) CS2+(B̃ 2Σu+)→S++CS owing to the potential curve crossing with the repulsive Σ−4 state correlated with the first dissociation limit.