Excitation of an Atom by Twisted Photons

TL;DR

This paper investigates how twisted photons with high angular momentum can excite atomic states, revealing new quantum state distributions when the photon beam is not aligned with the atom's center, supported by numerical calculations on hydrogen.

Contribution

It demonstrates how off-center twisted photon interactions relax traditional selection rules, leading to unique atomic excitation distributions not seen with plane-wave photons.

Findings

Twisted photons can excite a broader range of atomic states.

Off-center beam interactions produce distinct quantum number distributions.

Numerical results confirm the theoretical predictions.

Abstract

Twisted photon states, or photon states with large ($> \hbar$) angular momentum projection in the direction of motion, can photoexcite atomic final states of differing quantum numbers. If the photon symmetry axis coincides with the center of an atom, there are known selection rules that require exact matching between the quantum numbers of the photon and the photoexcited states. The more general case of arbitrarily positioned beams relaxes the selection rules but produces a distribution of quantum numbers of the final atomic states that is novel and distinct from final states produced by plane-wave photons. Numerical calculations are presented using a hydrogen atom as an example.