Scattering lengths for collisions between sodium and potassium atoms

The scattering lengths that characterize the low-energy elastic scattering of ²³Na atoms by ³⁹K, ⁴⁰K and ⁴¹K atoms, when they interact via the X ¹Σ⁺ and a ³Σ⁺ states of the NaK dimer, are calculated. The systematic variation of the short- and long-range parts of the interaction potentials reveals that the calculated scattering lengths are sensitive to uncertainties in the potentials. It is concluded that precise spectroscopic measurements of the least-bound ro-vibrational levels supported by the ground electronic state, which would reduce the uncertainties in both the molecular potentials, are needed for an accurate determination of the scattering lengths.