Ultrafast Extreme Ultraviolet Photoelectron Spectroscopy of Nonadiabatic Photodissociation of CS from B (Σ) State: Product Formation via an Intermediate Electronic State.

We studied nonadiabatic dissociation of CS from the B (Σ) state using ultrafast extreme ultraviolet photoelectron spectroscopy. A deep UV (200 nm) laser using the filamentation four-wave mixing method and an extreme UV (21.7 eV) laser using the high-order harmonic generation method were employed to achieve the pump-probe laser cross-correlation time of 48 fs. Spectra measured with a high signal-to-noise ratio revealed clear dynamical features of vibrational wave packet motion in the B state; its electronic decay to lower electronic state(s) within 630 fs; and dissociation into S(D), S(P), and CS fragments within 300 fs. The results suggest that both singlet and triplet dissociation occur via intermediate electronic state(s) produced by electronic relaxation from the B (Σ) state.