Dissociation energy of the hydrogen molecule at 10${}^{-9}$ accuracy

Abstract

The ionization energy of ortho-H${}_2$ has been determined to be $E_{\mathrm{I}}^{\mathrm{o}}({\mathrm{H}}_2)/(hc)=124357.238062(25)$ cm${}^{-1}$ from measurements of the GK(1,1)--X(0,1) interval by Doppler-free two-photon spectroscopy using a narrow band 179-nm laser source and the ionization energy of the GK(1,1) state by continuous-wave near-infrared laser spectroscopy. $E_{\mathrm{I}}^{\mathrm{o}}$(H${}_2$) was used to derive the dissociation energy of H${}_2$, $D_0^{N=1}$(H${}_2$), at $35999.582894(25)$ cm${}^{-1}$ with a precision that is more than one order of magnitude better than all previous results. The new result challenges calculations of this quantity and represents a benchmark value for future relativistic and QED calculations of molecular energies.

6 pages, 5 figures