Dissociation energies of the hydrogen and deuterium molecules

Fluorescence-excitation spectroscopy near [similar to]84 nm has been used to measure the threshold for the dissociation of H[sub 2]([ital B][prime] [sup 1][Sigma][sub [ital u]][sup +])=H(1[ital s])+H(2[ital s]) at 118 377.06[plus minus]0.04 cm[sup [minus]1] and the corresponding limit for D[sub 2] at 119 029.72[plus minus]0.04 cm[sup [minus]1]. The onset of dissociation was observed clearly, free from overlapping molecular lines, by the use of delayed quenching of 2[ital s] atoms produced by the photoexcitation pulse. These measurements have yielded the values [ital D][sub 0](H[sub 2])=36 118.11[plus minus]0.08 cm[sup [minus]1] and [ital D][sub 0](D[sub 2])=36 748.38[plus minus]0.07 cm[sup [minus]1] for the dissociation energies of the ground electronic states [ital X] [sup 1][Sigma][sub g][sup +], in agreement with the latest [ital ab] [ital initio] calculations, which include nonadiabatic, relativistic, and radiative corrections. From the present values and recently determined ionization energies of H[sub 2] and D[sub 2], the dissociation energies of the respective ions were found to be [ital D][sub 0](H[sub 2][sup +])=21 379.37[plus minus]0.08 cm[sup [minus]1] and [ital D][sub 0](D[sub 2][sup +])=21 711.64[plus minus]0.07 cm[sup [minus]1], also in agreement with recent [ital ab] [ital initio] calculations.