Trapping of cold atoms by the quadrupole force

TL;DR

This paper develops a theory beyond the dipole approximation showing that cold atoms can be trapped by quadrupole forces even without dipole transitions, expanding the understanding of atomic trapping mechanisms.

Contribution

It introduces a new theoretical framework considering quadrupole forces for trapping cold atoms, which was not previously explored in detail.

Findings

Quadrupole forces can trap atoms without dipole transitions.

Numerical examples for Ca and Na demonstrate trapping feasibility.

The theory extends trapping possibilities beyond conventional dipole-based methods.

Abstract

Cold atoms are traditionally trapped by the dipole force in periodically spaced potential wells induced by the standing laser field. We derive here a theory beyond the conventional dipole approximation which provides field/atom coupling potential terms that so far have not been taken into consideration in theoretical or experimental studies. We show that for some atoms for specific laser parameters despite the absence of dipole transition laser trapping is still possible due to the quadrupole force. Illustrative numerical calculations for Ca and Na trapped by the quadrupole force are given.