Reduced potential energy curves for diatomic molecules and their respective cations

It is shown that the reduced potential energy curve for a diatomic molecule and its cation are nearly identical, particularly near the minimum, implyi ng that the force constant in reduced variables is nearly the same for the two species. An explanation is given in terms of scaling of the valence-ele ctron wavefunction with respect to the nuclear coordinates. (C) 1999 Elsevi er Science B.V. All rights reserved.