Analysis of exchange energy at long range for states of alkali diatomic molecules correlating to two ground state atoms

Recently experimentally-based asymptotic exchange energies ΔVE between ground state atoms in Li2, Na2, K2, and NaK have been determined from spectroscopically-determined potential energy curves. These empirical results are shown to be well fit by the expression −CRαe−βR of Smirnov and Chibisov, where C is a positive constant and α and β can be readily calculated from the atomic ionization energies. The expression should be useful for estimating the exchange energy in other alkali dimers.