Pathway of H+ in fragmentation of H2 in 810 nm intense femtosecond laser fields

We experimentally measured the kinetic energy and angular distributions of fragment ion H+ of H-2 as a function of 810 nm femtosecond laser intensity by using velocity map imaging technique. The reaction pathways of dissociation channels H-2(+) -> H+ + H and H-2(2+) -> H+ + H+ are proposed. The analysis of the angular distribution indicates the net two-photon pathway via the 3 omega crossing dominates over the direct one-photon pathway in channel H-2(+) -> H+ + H. The ionization of H-2(+) to H-2(2+) may be initiated by bond softening and above-threshold dissociation. The relative yield of fragment peaks indicates that dissociation and ionization of H-2(+) are competitive. The lower laser intensities emphasize the dissociation probability of H-2(+), and the higher laser intensities favor higher ionization stages.