Potential energy curves for the a 3Σu+ and c 3Σ+g states of He2 consistent with differential scattering, a b i n i t i o theory, and low-temperature exchange rates

Crossed beam scattering experiments on He*(2 3S)+He at energies of 0.94, 1.51, and 2.24 kcal/mol have been combined with ab initio theory and kinetic data on metastability exchange rates to produce new estimates of the title potential energy curves. The long-range potential barrier in the a state is found to be 1.43±0.05 kcal/mol at a separation of 2.717±0.04 A. Combining these results with those for the corresponding singlet states from an earlier paper [J. Chem. Phys. 80, 5027 (1984)], we discuss the long-range behavior of the curves, particularly with respect to curve crossing between a given pair of g and u states. These crossings, which conform to theoretical predictions, appear to be essential for a consistent description of all available data.