IONIZATION RATES AND HARMONIC-GENERATION FOR H INTERACTING WITH LASER-PULSES OF LAMBDA=1064 NM AND PEAK INTENSITIES IN THE RANGE 2X10(13)-2X10(14)W CM(-2)

We applied the state-specific expansion approach (SSEA) to the solutio n of the time-dependent Schrodinger equation describing the interactio n of H with laser pulses of lambda = 1064 nm and peak intensities I-0 = 2 x 10(13), 6 x 10(13), 1 x 10(14) and 2 x 10(14) W cm(-2), and comp uted ionization rates and high-order harmonic spectra. For the first t hree cases, our results are compared with those of Krause and co-worke rs (Krause J L, Schafer K J and Kulander K C 1992 Phys. Rev. A 45 4998 ) who employed the grid method. Whereas for I-0 = 1 x 10(14) W cm(-2) convergence difficulties were reported for the grid method, no such di fficulties were found for the SSEA. Given this fact, we tackled the pr oblem of computing the harmonic spectrum for I-0 = 2 x 10(14) W cm(-2) , the most difficult case treated thus far. This spectrum shows a cut- off at the 65th harmonic (3.17 U-p + I-p) and an extended plateau cont aining low-intensity harmonics up to the 181st. The ionization rate is 1.7 x 10(13) s(-1) while at the end of the pulse 19.5% of the system is in the 1s ground state and 2.6% in the bound states up to n = 20, l = 19.