Refractive index for matter waves in ultracold gases - art. no. 023615

An analytical expression for the refractive index of atomic and molecular m atter waves in ultracold,oases is obtained. Asymptotic formulas for the ref ractive index are derived for high and low projectile velocities, and inter mediate velocities are investigated with the eikonal approximation. The rea l and imaginary parts of the matter wave refractive index are expressed via the complex scattering length of elastic and superelastic collisions. It i s shown that superelastic collisions dramatically influence the low-energy behavior of the refractive index. A discussion is given of proposed measure ments of the real and imaginary parts of the scattering length using the in terferometry of slow de Broglie waves.