S-wave scattering lengths and effective ranges for collisions of ground state Be atoms

The scattering lengths and effective ranges for collisions of ground state Be atoms interacting via the X1Σ+g molecular state of the Be2 dimer are calculated for two published X1Σ+g potentials. A new ab initio X1Σ+g potential is presented with its vibrational energies and rotational constants. The scattering parameters calculated with it and with the existing potentials are compared. Simple formulae showing how the scattering parameters are influenced by adiabatic coupling to electronic motion are derived within the semi-classical formulation and evaluated for the potentials considered. The formulae imply that a semi-classical account of adiabatic coupling can be made by increasing each atomic mass by one electron mass