Angular Momentum in Non-Relativistic QED and Photon Contribution to Spin of Hydrogen Atom

TL;DR

This paper develops a framework for analyzing angular momentum in non-relativistic QED, calculates photon contributions to hydrogen atom spin, and suggests potential experimental measurability.

Contribution

It constructs an effective angular momentum operator in NRQED, performs one-loop matching calculations, and quantifies photon contributions to atomic spin.

Findings

Photon contribution to hydrogen spin: m m m

First calculation of photon angular momentum in hydrogen ground state

Potential measurability in future atomic experiments

Abstract

We study angular momentum in non-relativistic quantum electrodynamics (NRQED). We construct the effective total angular momentum operator by applying Noether's theorem to the NRQED lagrangian. We calculate the NRQED matching for the individual components of the QED angular momentum up to one loop. We illustrate an application of our results by the first calculation of the angular momentum of the ground state hydrogen atom carried in radiative photons, $\alpha_{\rm em}^3/18\pi$, which might be measurable in future atomic experiments.