Strong-field photoionization of vibrational ground-state H2+ and D2+ molecules

We report on the observation of a high-energy "shoulder'' in the kinetic-energy distribution of H+ and D+ ions formed in the interaction of H-2 and D-2 with ultrashort light pulses of an intensity higher than approximately 10(15) W/cm(2). it extends up to a kinetic energy of approximate to 8 eV. The "shoulder" ions are formed by Coulomb explosion after photoionization bf the respective molecular ion. The shape of the ''shoulder'' indicates that photoionization of H-2(+) in the vibrational ground state v = 0 and of D-2(+) in v = 0,1 is the mechanism for atomic ion formation near the "shoulder" cutoff. [S1050-2947(99)06111-9].