Specular reflection of cold caesium atoms from a magnetostatic mirror

We have observed specular reflection and multiple bounces of a beam of laser-cooled caesium atoms from a magnetostatic mirror consisting of an array of rare-earth permanent magnets. Using a time-of-flight absorption technique, the reflection coefficient of the mirror for caesium 6(2)S(1/2), F = 4 atoms pumped toward the m = +4 state is determined to be (100 +/- 2)%. For a beam of unpolarized atoms the reflectivity is found to be unexpectedly high, (90 +/- 5)%, which is attributed to contributions from atoms in m = 0, -1, -2 states which are reflected at high magnetic fields close to the surface of the mirror as a result of the quadratic Zeeman effect.