Resonance dispersion interaction of alkali metal atoms in Rydberg states

Abstract

With the use of second-order perturbation theory in the long-range interatomic interaction for the degenerate states of two Rydberg atoms we have obtained a general formula for the dependence of atomic interaction energy on the interatomic distance R in the presence of the Förster resonance. Inside of the ‘Förster sphere’ (R < RF) this dependence transforms to the formula for electric dipole interaction energy ΔEd − d = C3/R3 and for R > RF it transforms to the formula for the van der Waals interaction energy ΔEVdW = −C6/R6. The van der Waals constant C6 is represented as an expansion in terms of irreducible components which define the dependence on the interatomic axis orientation relative to the quantisation axis of projections M of the total angular momentum J. The numerical values of the irreducible components of tensor C6 were calculated for rubidium atoms in the same Rydberg states |nlJM〉 with large quantum numbers n. We present the calculated resonance interaction energy of two rubidium atoms in the states |43D5/2M〉, whose total energy exceeds by only 8 MHz the total energy of one of the atoms in the state |45P3/2M〉 and of the other in the state |41F7/2M〉.