3I+ X? Electronic State Induced by Intense Few-Cycle Laser Fields]]>

摘要

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 (CH_(3)I~(+)) in the X? electronic state. Irradiation of CH_(3)I by 6 fs laser pulses with peak intensities of 1.9 × 10~(14) W/cm~(2) followed by femtosecond extreme ultraviolet probing of the iodine 4 d core-level transitions reveals dissociation of the CH_(3)I~(+) X? ~(2) E _(1/2) state with a time constant of 0.76 ± 0.16 ps. By contrast, the X? ~(2) E _(3/2) spin–orbit ground state does not exhibit any appreciable dissociation on the picosecond time scale. The observed spin–orbit state-selective dissociation of the X? state is rationalized in terms of the laser-induced coupling to the ? state. Our results suggest that the intense-laser control of photodissociation channels can be potentially extended to spin–orbit split states.