Channel-resolved multiorbital double ionization of molecular Cl2 in an intense femtosecond laser field

Abstract

We measure the sequential double ionization and the subsequent Coulomb explosion of molecular ${\mathrm{Cl}}_{2}$ in an intense femtosecond laser field by using the dc-sliced ion imaging technique. The results indicate that not only the highest occupied molecular orbital (HOMO) but also the next two lower-lying molecular orbitals are involved in three distinguished reaction pathways. Pathways ${(1,\phantom{\rule{0.28em}{0ex}}1)}^{2}$ and ${(1,\phantom{\rule{0.28em}{0ex}}1)}^{3}$ are both dissociated from ${\mathrm{Cl}}_{2}{\phantom{\rule{0.16em}{0ex}}}^{2+}\ensuremath{\rightarrow}{\mathrm{Cl}}^{+}+{\mathrm{Cl}}^{+}$, but with the two electrons removed from HOMO and HOMO-2 in reverse sequence, and populated on the ionic excited states $^{3}\mathrm{\ensuremath{\Pi}}_{g}$ and $^{1}\mathrm{\ensuremath{\Pi}}_{g}$, respectively. The kinetic energy release differences observed in these two channels are ascribed to the nuclear motion during the ionization process. For pathway ${(1,\phantom{\rule{0.28em}{0ex}}1)}^{1}$ (also dissociated from ${\mathrm{Cl}}_{2}{\phantom{\rule{0.16em}{0ex}}}^{2+}\ensuremath{\rightarrow}{\mathrm{Cl}}^{+}+{\mathrm{Cl}}^{+}$) populated on the ionic excited states $^{1}\mathrm{\ensuremath{\Pi}}_{g}$, the isotropic angular distribution of the fragment ions is attributed to the combination of the electron density distribution of HOMO-1, the vibrational electronic wave-packet evolution, and the field excitation. Our results propose a feasible method to manipulate the electronic dynamics which takes place in the attosecond time domain via accurately tuned laser parameters of a femtosecond laser field.