Ionization and dissociation energies of HD and dipole-induced g/u -symmetry breaking

Abstract

The ionization energy of HD has been determined to be EI(HD)=124568.48466(7)cm-1 by two-photon Doppler-free vacuum-ultraviolet pulsed laser spectroscopy, near-infrared continuous-wave laser spectroscopy, and Rydberg-series extrapolation by multichannel quantum-defect theory (MQDT). From this value, the dissociation energy of HD is deduced to be D0(HD)=36405.78253(7)cm-1, representing a fivefold improvement over previous values and resolving a 3.2σ disagreement with ab initio calculations of the four-particle nonadiabatic relativistic energy and of quantum-electrodynamic corrections up to order mα6. Interactions between d, f, and g Rydberg series have been observed and had to be included in the MQDT extrapolation of the Rydberg series.