Dissociation of H-2(+) and D-2(+) in an intense laser field

We report experimental investigations on dissociation of H-2 and D-2 in intense subpicosecond laser pulses at 1053 and 526.5 nm. Intensities in the range from approximate to 5 X 10(13) up to approximate to 5 x 10(14) W/cm(2) were applied. The kinetic-energy distributions of the photoions H+ and D+, which change dramatically with the light pulse peak intensity, give a detailed insight into the dissociation mechanisms. At 526.5 nm and low light intensity, ions from bond-softening dissociation and probably seven-photon resonant dissociative multiphoton ionization dominate the spectra. The resonant intermediate states are Rydberg states of the neutral molecules. At 1053 nm, above-threshold dissociation makes the main contribution to the spectra. Independent of the excitation wavelength, Coulomb explosion dissociation is found in the high-intensity limit. H-2(+) and D-2(+) photoionization, triggering this process, proceeds in the quasistatic limit by preferred tunnel or above-barrier ionization in a limited range of internuclear separations around 7.5 a.u. The ion kinetic-energy distributions seem to indicate that at 526.5 nm ionization starts from molecular ions light stabilized in a certain range of internuclear distances. In contrast, at 1053 nm, ionization seems to start from dissociating molecular ions.