New analytical potential energy function for diatomic cations

A new analytical potential function for doubly charged diatomic ions is proposed as [GRAPHICS] where a(n), a(k+1) and C are parameters, and R is the nuclear distance. This function can be used to describe the potential curves for doubly charged diatomic ions with both potential minimum and maximum, or without any stationary point. As examples, potential functions of this form for ground states of Be-2(2+), He-2(2+) and HF2+ have been derived for the first time. The calculations using the theoretical method QCISD with basis set 6-311+ + G* have showed the potential minimum of Be-2(2+) is at R-min= 0.214 nm, the maximum at R-max = 0.350 nm, and DeltaE = E-max - E-min = 1.07 eV; for He-2(2+), R-min= 0.0736 nm, R-max = 0. 105 nm, and DeltaE = E-max - E-min = 0.71 eV. It is found that the potential curve for HF2+ is one with singly repulsive branch. The force constants and spectroscopic data for Be-2(2+) and He-2(2+) have also been work out. (C) 2004 Elsevier B.V. All rights reserved.