Measurement of the refraction index for atom waves

Abstract

We have developed a Mach-Zehnder atom interferometer which uses elastic diffraction of lithium atom on laser standing waves for the coherent manipulation of the atom wave. The interference signal is of sufficient quality to achieve a phase sensitivity near 10 milliradians/√Hz. With this apparatus, we have recently measured the index of refraction of several gases for lithium waves. The interference signals give access to the real and imaginary parts of (n - 1) and we have tested the linear dependence of these two quantities with gas density. The measured values of (n-1) are in good agreement with calculations and they exhibit glory oscillations, as predicted by theory.