Determination of the ionization and dissociation energies of the deuterium molecule (D2)

Abstract

The transition wave numbers from selected rovibrational levels of the EF (1)Sigma(g) (+)(v=0) state to selected np Rydberg states of ortho- and para-D(2) located below the adiabatic ionization threshold have been measured at a precision better than 10(-3) cm(-1). Adding these wave numbers to the previously determined transition wave numbers from the X (1)Sigma(g) (+)(v=0, N=0,1) states to the EF (1)Sigma(g) (+)(v=0, N=0,1) states of D(2) and to the binding energies of the Rydberg states calculated by multichannel quantum defect theory, the ionization energies of ortho- and para-D(2) are determined to be 124 745.394 07(58) cm(-1) and 124 715.003 77(75) cm(-1), respectively. After re-evaluation of the dissociation energy of D(2) (+) and using the known ionization energy of D, the dissociation energy of D(2) is determined to be 36 748.362 86(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 36 748.3633(9) cm(-1) [K. Piszczatowski, G. Łach, M. Przybytek et al., J. Chem. Theory Comput. 5, 3039 (2009)]. The ortho-para separation of D(2), i.e., the energy difference between the N=0 and N=1 rotational levels of the X (1)Sigma(g) (+)(v=0) ground state, has been determined to be 59.781 30(95) cm(-1).