Spin-Orbit State-Selective C-I Dissociation Dynamics of the CHI X̃ Electronic State Induced by Intense Few-Cycle Laser Fields.

Studies of ultrafast molecular dynamics induced by intense laser fields can reveal new approaches to manipulating chemical reactions in the strong-field regime. Here, we show that intense few-cycle laser pulses can induce the spin-orbit state-selective C-I dissociation of the iodomethane cation (CHI) in the X̃ electronic state. Irradiation of CHI by 6 fs laser pulses with peak intensities of 1.9 × 10 W/cm followed by femtosecond extreme ultraviolet probing of the iodine 4d core-level transitions reveals dissociation of the CHI X̃ E state with a time constant of 0.76 ± 0.16 ps. By contrast, the X̃ E spin-orbit ground state does not exhibit any appreciable dissociation on the picosecond time scale. The observed spin-orbit state-selective dissociation of the X̃ state is rationalized in terms of the laser-induced coupling to the à state. Our results suggest that the intense-laser control of photodissociation channels can be potentially extended to spin-orbit split states.