Relaxation of the sodium atom in the 4D level by collisions with noble gases. II. Theoretical aspects

2014 In previous papers [1-3] we have reported experimental measurements of the relaxation rates of the k-multipole moments in the 4D level of sodium and the 3S-4D optical coherence. In the present paper we compare the experimental values with those obtained theoretically for different types of potentials. We show that the Van der Waals C6R -6 interaction is not sufficiently anisotropic to describe the relaxation of the k multipole moments. For Ar, Kr and Xe, much better results are obtained by taking into account the next term C8R-8 in the expansion of the long-range interaction. The potentials of Pascale and Vandeplanque [4] give very good results for helium. The results are also satisfactory for Ar, Kr and Xe, but the agreement could still be improved. LE JOURNAL DE PHYSIQUE TOME 40, JUIN 1979,