High-Multipole Excitations of Hydrogen-Like Atoms by Twisted Photons near Phase Singularity

TL;DR

This paper investigates how twisted photons with high angular momentum can excite hydrogen-like atoms near phase singularities, revealing significant transition rates into high orbital angular momentum states and singular cross sections at vortex centers.

Contribution

It provides the first detailed calculation of transition amplitudes and cross sections for high-multipole excitations of atoms by twisted photons near phase singularities.

Findings

High transition rates into states with orbital angular momentum l_f>1 near vortex center

Cross sections become singular at the optical vortex center

Transition rates normalized to local photon flux are comparable to electric dipole transitions

Abstract

We calculate transition amplitudes and cross sections for excitation of hydrogen-like atoms by the twisted photon states, or photon states with angular momentum projection on the direction of propagation exceeding $\hbar$. If the target atom is located at distances of the order of atomic size near the phase singularity in the vortex center, the transitions rates into the states with orbital angular momentum $l_f>1$ become comparable with the rates for electric dipole transitions. It is shown that when the transition rates are normalized to the local photon flux, the resulting cross sections for $l_f>1$ are singular near the optical vortex center. Relation to the "quantum core" concept introduced by Berry and Dennis is discussed.