The X(1)(2)Pi(3/2) and X(2)(2)Pi(1/2) Potential Energy Surfaces of FO

The X(1)(2)Pi(3/2) and X(2)(2)Pi(1/2) potential energy curves of the FO free radical have been determined from a fit to the available high-resolution spectroscopic data. The data set spans the vibrational states v = 0-7 and includes X(2)(2)Pi(1/2) <-- X(1)(2)Pi(3/2) fine-structure transitions. The determinable spectroscopic constants provide an excellent description of the equilibrium properties of both the X(1) and X(2) states in addition to the vibrational dependence of the spin-orbit coupling constant. The experimental properties of FO are used to evaluate the performance of different ab initio methods for describing the F-O bond. Copyright 2001 Academic Press.