Multiparameter model functions in problems of approximating ab initio potentials and spectroscopic data of diatomic molecules

A new multiparameter function of the generalized Morse long-range potential is presented. All earlier similar constructions turn out to be particular cases of this new function. The operation technique for this function is described. Using realistic test examples (ab initio potentials of the K 2 molecule and “experimental” spectroscopic data calculated by them), the possibilities of this function are compared with those of the most developed form of the piecewise continuous model potential in problems of direct optimization modeling of potential functions and in problems of optimization modeling of experimental data aiming at determining potentials. A conclusion is drawn that, although the two classes of functions lead, in general, to comparable results in quality, the piecewise continuous approximant permits one to achieve a better reproduction of the modeled data in some cases. Using the available collection of experimental data, parameters of the piecewise continuous approximant were determined for the potentials of the 1 g (3 3 Π g ) and a 3 Σ u + states of the Cs 2 molecule, for which we previously constructed potentials in the form of a generalized Morse function (J. Chem. Phys. 135 , 024303 (2011)).