Kinetic-energy–angle differential distribution of photofragments in multiphoton above-threshold dissociation ofD2+by linearly polarized400−nmintense laser fields: Effects of highly excited electronic states

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We have performed a detailed calculation of the double-differential angular\char21{}kinetic-energy distribution of photofragments in above threshold dissociation (ATD) of $\mathrm{D}_{2}{}^{+}$ from initial vibrational-rotational levels ${v}_{i}=4,5$ and ${J}_{i}=0,1$ in an intense linearly polarized laser field of wavelength $400\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ and intensity $3\ifmmode\times\else\texttimes\fi{}{10}^{13}\phantom{\rule{0.3em}{0ex}}\mathrm{W}∕{\mathrm{cm}}^{2}$. The calculation used a time-independent close-coupling (CC) formalism with eight (ten) electronic states included in the basis-set expansion of the molecular wave function. The molecular electronic states included, apart from the two lowest $1s{\ensuremath{\sigma}}_{g}$ and $2p{\ensuremath{\sigma}}_{u}$ states, were $2p\ensuremath{\pi}_{u}{}^{\ifmmode\pm\else\textpm\fi{}}$, $2s{\ensuremath{\sigma}}_{g}$, $3p{\ensuremath{\sigma}}_{u}$, $3d{\ensuremath{\sigma}}_{g}$, $3d\ensuremath{\pi}_{g}{}^{\ifmmode\pm\else\textpm\fi{}}$, and $4f{\ensuremath{\sigma}}_{u}$. All the higher electronic states dissociate to the atomic state $\mathrm{D}(2\ensuremath{\ell})$. A sufficient number of photon absorption channels, $n=0\char21{}7$, and molecular rotational quantum numbers $J=0\char21{}11$ were taken into account to ensure the convergence of the multiphoton ATD probability. Altogether 198 coupled channels had to be considered in the calculation. The calculations reveal signatures of significant ejection of the photodissociation fragments away from the laser polarization direction due to the inclusion of the higher excited electronic states. The ratio of the photofragments perpendicular to and along the polarization axis shows good quantitative agreement with the experimental result. The angular distributions show considerable structures depending on the relative kinetic energies of the photofragments, and the fragments with different kinetic energies show peaks at different dissociation angles.