LIGHT-INDUCED TORQUE ON MOVING ATOMS

We show that a two-level atom moving in a Laguerre-Gaussian beam is subject to a light-induced torque, T, about the beam axis which is directly proportional to l, the orbital angular momentum quantum number of the mode. The torque, which has a Lorentzian frequency response which includes an azimuthal l-dependent Doppler shift in the detuning term, reduces in the saturation limit to the simple form T almost-equal-to HBARlGAMMA, where 2GAMMA is the decay rate of the excited state.