Anisotropic interactions in electric field polarized ultracold Rydberg gases

We calculate pair potential curves for interacting Rydberg atoms in a constant electric field and use them to determine the effective C3 dipole-dipole and C6 van der Waals coefficients. We compare the C3 and C6 with experiments where the angle of a polarizing electric field is varied with respect to the axis of a quasi-1-dimensional trap at ultracold temperatures. The dipoles produced via polarization of the atoms have an angular dependent dipole-dipole interaction. We focus on the interaction potential of two rubidium Rydberg atoms in 50 S 1 2 states in the blockade regime. For internuclear distances close to the blockade radius, Rbl 4-6 m, molecular calculations are in much better agreement with experimental results than those based on the properties of single atoms and independent calculations of C3 and C6 which were used to analyze the original experiment. We find that the calculated C6 coefficient is within 8% of the experimental value while the C3 coefficient is within 20% of the experimental value.