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 atoms pumped toward the m=+4 state is determined to be . For a beam of unpolarized atoms the reflectivity is found to be unexpectedly high, , 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.