Determination of the ionization and dissociation energies of the deuterium molecule $(D2)$ Available to Purchase

The transition wave numbers from selected rovibrational levels of the $EFΣ1g+(v=0)$ state to selected $np$ Rydberg states of ortho- and para-$D2$ located below the adiabatic ionization threshold have been measured at a precision better than $10−3cm−1$⁠. Adding these wave numbers to the previously determined transition wave numbers from the $XΣ1g+(v=0,N=0,1)$ states to the $EFΣ1g+(v=0,N=0,1)$ states of $D2$ and to the binding energies of the Rydberg states calculated by multichannel quantum defect theory, the ionization energies of ortho- and para-$D2$ are determined to be $124745.39407(58)cm−1$ and $124715.00377(75)cm−1$⁠, respectively. After re-evaluation of the dissociation energy of $D2+$ and using the known ionization energy of D, the dissociation energy of $D2$ is determined to be $36748.36286(68)cm−1$⁠. This result is more precise than previous experimental results by more than one order of magnitude and is in excellent agreement with the most recent theoretical value $36748.3633(9)cm−1$ [K. Piszczatowski, G. Łach, M. Przybytek et al., J. Chem. Theory Comput. 5, 3039 (2009)]. The ortho-para separation of $D2$⁠, i.e., the energy difference between the $N=0$ and $N=1$ rotational levels of the $XΣ1g+(v=0)$ ground state, has been determined to be $59.78130(95)cm−1$⁠.