Associative detachment of H−+ H→H2+e−

Abstract

Using a merged-beams apparatus, we have measured the associative detachment (AD) reaction of ${\mathrm{H}}^{\ensuremath{-}}+\mathrm{H}\ensuremath{\rightarrow}{\mathrm{H}}_{2}+{e}^{\ensuremath{-}}$ for relative collision energies up to $E$${}_{\mathrm{r}}\ensuremath{\le}4.83$ eV. These data extend above the 1-eV limit of our earlier results. We have also updated our previous theoretical work to account for AD via the repulsive ${}^{2}{\ensuremath{\Sigma}}_{\mathrm{g}}^{+}$ H${}_{2}$${}^{\ensuremath{-}}$ potential energy surface and for the effects at ${E}_{\mathrm{r}}\ensuremath{\ge}0.76$ eV on the experimental results due to the formation of long-lived 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 ${E}_{\mathrm{r}}\ensuremath{\gtrsim}2$ eV. Similar behavior has been predicted for the formation of protonium from collisions of antiprotons and hydrogen atoms.