The spatial distribution in high-order harmonic generation of H2+ with different time delays of the two-color laser fields

We theoretically investigate the high-order harmonic generation (HHG) and the spatial distribution in HHG of the HI molecule by introducing a time-delayed two-color laser field which consists of the mid infrared and near-infrared later field. For the different time delays of the two-color laser fields, the pulse shapes are changed which result in the variation of the electron recombined with the nuclei along the positive- or negative-z direction. When the time delay is 0 fs (134 fs), a smooth harmonic plateau from the electron recombined with the nuclei along the negative (positive)-z direction can be achieved. An isolated attosecond pulse with a duration of about 99 as is generated when the time delay is 1.34 fs. We perform the classical analysis which is consistent with the numerical results from the one-dimensional non-Born-Oppenheimer time dependent Schrodinger equation (TDSE). We also investigate emission time of harmonics in terms of a time-frequency analysis to further understand the underlying physical mechanism. (C) 2016 Elsevier B.V. All rights reserved.