Mapping electron dynamics in molecular H2using high-order-harmonic-generation time profiles

The mechanism of the formation of doorway quasistates (transient species) prior to the start of ionization of the two-electron molecular H${}_{2}$ system subjected to an eight-cycle ultrashort intense laser pulse is investigated by solving exactly the one-dimensional (1D) electronic time-dependent Schr\"odinger equation, including nuclear motion semiclassically. Space of the electron density of the two-electron 1D H${}_{2}$ system around the nuclei is partitioned into four physicochemically significant partitions, including homolytic $({e}_{1}{\mathrm{H}}_{\ensuremath{\alpha}}^{+}\ensuremath{-}{\mathrm{H}}_{\ensuremath{\beta}}^{+}{e}_{2})\ensuremath{\sim}({e}_{2}{\mathrm{H}}_{\ensuremath{\alpha}}^{+}\ensuremath{-}{\mathrm{H}}_{\ensuremath{\beta}}^{+}{e}_{1})$ and ionic $({\mathrm{H}}_{\ensuremath{\alpha}}^{+}\ensuremath{-}{\mathrm{H}}_{\ensuremath{\beta}}^{\ensuremath{-}})\ensuremath{\sim}({\mathrm{H}}_{\ensuremath{\alpha}}^{\ensuremath{-}}\ensuremath{-}{\mathrm{H}}_{\ensuremath{\beta}}^{+})$ transient species. The underlying mechanisms responsible for the formation and evolution of the homolytic and ionic transient species are explored based on probing variation of the two-electron norms of these states and their corresponding time-dependent high-order harmonic generation spectra.