Fig. 3.

Correlation diagram and kinetic energy distribution for dissociation of ${\mathrm{H}}_2^{+}$ a Potential energy curves for the ground state of H₂ (lower curve) and the $1s{\sigma }_{\mathrm{g}}$, $2s{\sigma }_{\mathrm{g}}$, and $2p{\sigma }_{\mathrm{u}}$ ionization thresholds (upper curves). The latter correspond to electronic states of ${\mathrm{H}}_2^{+}$. The violet shaded area represents the Franck-Condon region associated to the ground vibrational state of H₂. Notice the break in the energy scale for a better visualization. The dashed violet line shows how the initial internuclear distance of the molecule is mapped onto the kinetic energy release (KER) of the reaction applying the”reflection approximation”⁹. b KER distribution obtained after single-photon ionization of H₂ employing photons of hν = 400 eV. Symbols: experiment, lines: theory. The calculation depicted by the black curve includes the twelve states with the highest photo ionization cross sections (up to n = 4). The main contributions (besides $1s{\sigma }_{\mathrm{g}}$ at low KER) are shown in blue ($2s{\sigma }_{\mathrm{g}}$) and red ($2p{\sigma }_{\mathrm{u}}$), others are not visible on that scale. The shaded areas indicate the regions of KER selected in Figs. 2d–f and 4a, c