Optical angular momentum in atomic transitions: a paradox

Abstract

Stated simply the paradox is as follows: it is clear that the orbital angular momentum of a light beam in its direction of propagation is an intrinsic quantity, and therefore has the same value everywhere in the beam. How then can a Gaussian beam, with precisely zero orbital angular momentum, drive a (single-photon) quadrupole transition which requires the transfer of angular momentum 2$\hslash$ to an absorbing atom?

Submitted to J.Phys.A. Special Issue "Claritons and the Asymptotics of Ideas: the Physics of Michael Berry"

References in corpus (3)

• Angular Momenta and Spin-Orbit Interaction of Nonparaxial Light in Free Space
• Conservation of the spin and orbital angular momenta in electromagnetism
• Enhancement of the quadrupole interaction of an atom with guided light of an ultrathin optical fiber