Detailed instantaneous ionization rate of H2+ in an intense laser field

Abstract

Component instantaneous ionization rate (IIR) is introduced and the approach of its calculation is formulated. The component IIR's and the overall (time-averaged) component ionization rates are calculated for H2+ at different values of internuclear distance in a linearly polarized laser field with I=1.0× 1014 W/cm2 intensity and λ=1064 nm wavelength by direct numerical solution of the fixed-nuclei full dimensional time-dependent Schrödinger equation. The exact overall component ionization rates calculated by time-averaging of the component IIR are compared with those calculated approximately via the virtual detector (VD) method. Details of the time-dependent behavior of the outgoing and incoming electron wave packets of the H2+ system in intense laser field at subfemtosecond time scale are studied based on the calculated component IIR. It is shown clearly that the positive (outgoing electron wave packet) signals of the IIR and its z component are strong and sharp but the negative (returning electron wave packet) signals of the IIR are smooth and weak. The structure of the ρ component of the IIR has smooth structure. Relation between the R -dependent ionization rate and duration of the ramp of the laser pulse is studied and it is explicitly shown that for internuclear distance R<5.6, when the laser pulse is turned on without a ramp, the first peak of R -dependent ionization rates moves towards the peak of the lower time-dependent Floquet quasienergy state (QES). © 2006 The American Physical Society.