Can a linearly polarized light beam polarize atomic spin?

Lax et al. [Phys. Rev. 11 (1975) 1365] discovered that a light beam in vacu um is not a transverse wave but does have a longitudinal field component. W e investigate atomic and molecular electric dipole transitions induced by s uch a light beam, in particular, linearly polarized in a transverse plane. We derive the selection rules and the transition rates for various quantiza tion axes using the paraxial approximation up to the first order of 1/kw. w here k is the wave number and w is the transverse size of the light beam. T he light beam is able to yield atomic spin polarization in the direction pe rpendicular to both the optical axis and the transverse electric field, and its magnitude is approximately 1/kw times that generated by a circularly p olarized light wave with the similar intensity. (C) 2001 Elsevier Science B .V. All rights reserved.