Dissociation energy of the hydrogen molecule

Fluoresence-excitation spectroscopy near 84.5 nm has been used to measure the threshold for the dissociation limit of ${\mathrm{H}}_{2}$(B' $^{1}\mathrm{\ensuremath{\Sigma}}_{\mathit{u}}^{+}$)=H(1s)+H(2s) at 118 377.06\ifmmode\pm\else\textpm\fi{}0.04 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. This yields a value of ${\mathit{D}}_{0}$(${\mathrm{H}}_{2}$)=36 118.11\ifmmode\pm\else\textpm\fi{}0.08 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ for the dissociation energy of the ground electronic state X${(}^{1}$${\mathrm{\ensuremath{\Sigma}}}_{\mathit{g}}^{+}$) of ${\mathrm{H}}_{2}$, in agreement with the latest theoretical calculation which includes nonadiabatic, relativistic, and radiative corrections. When combined with recent determinations of the ionization energy of ${\mathrm{H}}_{2}$ the present ${\mathit{D}}_{0}$(${\mathrm{H}}_{2}$) leads to the value ${\mathit{D}}_{0}$${\mathrm{H}}_{2}^{+}$)=21 379.36\ifmmode\pm\else\textpm\fi{}0.08 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, also in good agreement with theoretical values.