Scattering of hydrogen atoms at low temperature

A non-adiabatic model is employed to investigate the H-H scattering at low temperatures. Unlike molecular-orbital calculation technique, no separate calculations are required to obtain the potential energies of electrons in the field of hadrons. This model generates the non-adiabatic effective potential automatically. The coeffcients of van der Waals and higher-order potentials are estimated in the present model and are found to be in very good agreement with the corresponding standard values. The s-wave singlet and triplet scattering lengths and thermal-average total triplet cross-section at 2K are reported and compared with the existing theoretical and experimental predictions.