Optical angular momentum in atomic transitions: a paradox

• URL: http://arxiv.org/abs/2203.03742v1
• Date: Mon, 7 Mar 2022 22:06:18 GMT
• Title: Optical angular momentum in atomic transitions: a paradox
• Authors: Stephen M. Barnett, Fiona C. Speirits and Mohamed Babiker
• Abstract summary: 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$hbar$ to an absorbing atom?
• Score: 0.0
• License: http://creativecommons.org/licenses/by-nc-nd/4.0/
• 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$\hbar$ to an absorbing atom?

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