Dissociation Energy of the HD Molecule

Fluorescence excitation spectra of HD near the 84-nm region exhibit two dissociation limits which are interpreted as arising from production of the fragments H(2s) + D(1s) and H(1s) + D(2s). When the former products are associated with the lower energy limit, a value of D0(HD) = 36 405.83 ± 0.10 cm−1 is found for the dissociation energy of HD in the ground electronic state, in agreement with ab initio calculations. However, the higher energy limit indicates a discrepancy with this value, of almost 10 times the error of measurement, and requires theoretical treatment.