Light-induced rotational effects in atom guides

We show that atomic motion in a hollow cylindrical waveguide of circular cr oss section is subject to a quantised torque arising from the orbital angul ar momentum effects associated with any excited waveguide mode of order l > 0. In addition to its axial motion due to light pressure, an appropriately detuned atom immersed in such a mode may be trapped radially in vibrationa l states and be made to exhibit novel rotational effects associated with th e light torque, including the recently predicted rotational frequency shift . (C) 1999 Elsevier Science B.V. All rights reserved.