Application of numerical and analytical methods for reduction of IR and MW spectra of diatomic molecules to radial functions for the X1Σ+ states of GeS, BrCl, GaH, and ArH+:: further evidence of the inadequacy of the Radiatom procedure

Using Coxon's numerical SSPOT and Molski's analytical DS-cP fitting procedures, the IR and MW spectra of GaH X(1)Sigma(+), GeS X0(+), BrCl X0(+), and ArH+ X(1)Sigma(+) are reduced to radial potential energy and Born-Oppenheimer (BO) breakdown functions. The compact sets of fitted radial parameters differ significantly from those given by Ogilvie's analytical approach, as implemented in the computer program Radiatom. The calculations demonstrate unequivocally that the Radiatom program generates functions that reproduce the rotational and vibration-rotational energy levels of GaH, GeS, BrCl, and ArH+ with much less accuracy than those from the SSPOT and DS-cP programs. Since the radial functions obtained by Ogilvie are of doubtful physical significance and are thus meaningful only within the Radiatom program, they cannot be exported to external procedures that require physically significant functions. The reliability of estimates from field-free data of the rotational g-factors and electric dipole moments for GaH, GeS, BrCl, and ArH+ are also discussed. (C) 2003 Elsevier Inc. All rights reserved.