Metastable neon collisions : anisotropy and scattering length

In this paper we investigate the effective scattering length a of spin-polarized Ne*. Due to its anisotropic electrostatic interaction, its scattering length is determined by five interaction potentials instead of one, even in the spin-polarized case, a unique property among the Bose condensed species and candidates. Because the interaction potentials of Ne* are not known accurately enough to predict the value of the scattering length, we investigate the behavior of a as a function of the five phase integrals corresponding to the five interaction potentials. We find that the scattering length has five resonances instead of only one and cannot be described by a simple gas-kinetic approach or the degenerate internal state (DIS) approximation. However, the probability for finding a positive or large value of the scattering length is not enhanced compared to the single-potential case. We find that the induced dipole-dipole interaction enables strong coupling between the different |JPMP states, resulting in an inhomogeneous shift of the resonance positions and widths in the quantum-mechanical calculation as compared to the DIS approach. The dependence of the resonance positions and widths on the input potentials turns out to be rather straightforward. The existence of two bosonic isotopes of Ne* enables us to choose the isotope with the most favorable scattering length for efficient evaporative cooling towards the Bose-Einstein condensation transition, greatly enhancing the feasibility to reach this transition