Ground State D₂ Dissociation Energy from the Near-dissociation Behavior of Rotational Level Spacings

Abstract

A method of determining the dissociation energy of a diatomic molecule from the rotational term value(s)of a single vibrational level lying near dissociation is derived and tested. It is based on expressions relating the characteristic near-dissociation behavior of the rotational constants B v , D v , H v ,… etc., to the asymptotically dominant inverse power contribution to the long range intermolecular potential. Application of this procedure to data for ground state D 2 yields a dissociation energy of D 0 = 36 748.88(±0.3)cm −1 , in essentially exact agreement with the value Herzberg determined from the onset of continuum absorption in the vacuum u.v., 36 748.9(±0.4) cm −1 . This agreement between results obtained from completely different observables appears to confirm the existence of a small discrepancy between experiment and the most recent theoretical nonadiabatic dissociation energy of Kolos and Wolniewicz, 36 748.2 cm −1 .