Mass dependence of scattering lengths for hydrogen atoms

We demonstrate that changing the reduced mass in scattering calculations is equivalent to changing the potential. We explore how small changes in the mass alter the scattering length of hydrogen atoms when they interact via the X¹Σg⁺ and b³Σᵤ⁺ molecular states. We show how the variation of scattering length with mass depends on the asymptotic potential.