Potential scattering and spin-exchange cross sections in atomic hydrogen at very low energies

Potential scattering and spin-exchange scattering cross sections in the energy range from 10-3 cm-1 to 100 cm-1 have been calculated numerically for hydrogen atoms in collision based on the most accurate Kolos-Woniewicz adiabatic potentials available at present. The scattering lengths for the singlet and triplet states are calculated to be a0s = 0.595 a.u. and a0t = 1.34 a.u., respectively. The quasi-bound state with v = 14 and l = 4 is found to be at E = 1.675 cm-1 above the dissociation limit. The thermally averaged spin-exchange cross section has the low temperature limit σ-barex(0 K) = 0.982 A2 with a minimum σ-barex(2.5 K) = 0.329 A2. (author)