DISSOCIATION OF H-2(-2(+) IN AN INTENSE LASER FIELD() AND D)

We report experimental investigations on dissociation of H-2 and D-2 i n 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 p hotoions H+ and D+, which change dramatically with the light pulse pea k intensity, give a detailed insight into the dissociation mechanisms. At 526.5 nm and low light intensity, ions from bond-softening dissoci ation and probably seven-photon resonant dissociative multiphoton ioni zation dominate the spectra. The resonant intermediate states are Rydb erg states of the neutral molecules. At 1053 nm, above-threshold disso ciation 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 t his process, proceeds in the quasistatic limit by preferred tunnel or above-barrier ionization in a limited range of internuclear separation s around 7.5 a.u. The ion kinetic-energy distributions seem to indicat e that at 526.5 nm ionization starts from molecular ions light stabili zed in a certain range of internuclear distances. In contrast, at 1053 nm, ionization seems to start from dissociating molecular ions.