Associative Detachment of H^{- + H $\to$ H${}_2$ + e${}^{-}$

Using a merged beams apparatus we have measured the associative detachment (AD) reaction of ${\mathrm{H}}^{-}+\mathrm{H}\to {\mathrm{H}}_2+e^{-}$ for relative collision energies up to $\mathit{\text{E}}$${}_{\mathrm{r}}\le 4.83$ eV. These data extend above the 1 eV limit of our earlier results. We have also updated our previous theoretical work to account for AD via the repulsive ${}^2{\mathrm{\Sigma }}_{\mathrm{g}}^{+}$ H${}_2^{-}$ potential energy surface and for the effects at $E_{\mathrm{r}}\ge 0.76$ eV on the experimental results due to the formation of H${}_2$ resonances lying above the $\mathrm{H}+\mathrm{H}$ separated atoms limit. Merging both experimental data sets, our results are in good agreement with our new theoretical calculations and confirm the prediction that this reaction essentially turns off for $E_{\mathrm{r}}\gtrsim 2$ eV. Similar behavior has been predicted for the formation of protonium from collisions of antiprotons and hydrogen atoms.