Scattering lengths for collisions of hydrogen and deuterium atoms

The scattering lengths for hydrogen and deuterium atoms interacting via the potentials of the X ¹ σ_g⁺, b ³ σ_u⁺ and e ³ σ _u⁺ molecular states are calculated. An estimate of the uncertainty in the X ¹ σ_g⁺ scattering length arising from the coupling to the ¹ σ_u ⁺ states is made. The recommended scattering lengths are -0.67 and 148 bohr for the b ³ σ_u⁺ and e ³σ_u⁺ interaction potentials, respectively, and 11.1 bohr for the X ¹ σ_g ⁺ interaction potential. It is suggested that deuterium atoms would be cooled efficiently by collisions with metastable hydrogen atoms.