Remark on the ground state potentials and dissociation energies of the alkali hydrides

Abstract

The ground state Rydberg—Klein—Rees (RKR) potentials and the corresponding molecular constants of the alkali hydrides, recommended in a recent article by S twalley et al. ( J. Phys. Chem. Ref. Data, to be published [1]) are critically evaluated in the framework of the reduced potential curve (RPC) scheme. A comparison with the older RPC analysis of the ground states of the alkali hydrides is briefly discussed. The efficiency of the RPC method for the detection of errors in the RKR potential (spectroscopic constants) and for the estimation of the dissociation energy is emphasized. Although the RKR potentials of NaH and RbH are known only up to 54 and 57% of D e, respectively, the RPC method permitted here at least a substantial reduction of the uncertainty in the lower limit of D e(NaH) (by 70 cm −1) and in the lower and upper limits of D e(RbH) (by 250 and 500 cm −1, respectively) which are now estimated as 15 870, 14 230 and 14 680 cm −1, respectively. The RPC picture even suggests that the values 14 380 and 14 580 cm −1 may possibly be taken as reasonable limits for D e(RbH). Accurate extensions of the inner wings of the potentials of NaH, RbH and CsH were calculated using the generalized reduced potential curve (GRPC) method. The limit of error of these extensions should be smaller than 0.002 Å if the potentials are correct.