Trapping ions with lasers

TL;DR

This paper provides a theoretical analysis of ion trapping using lasers, focusing on the effects of net charge and including detailed electromagnetic interactions, with findings indicating these effects are minimal compared to dominant dipolar terms.

Contribution

It introduces a comprehensive theoretical model for laser trapping of ions, incorporating charge monopole effects and center of mass motion within a multipolar interaction framework.

Findings

Charge monopole correction is of order m_e/M.

Additional laser coupling effects are very small.

Dipolar trapping remains the dominant interaction.

Abstract

This work theoretically addresses the trapping an ionized atom with a single valence electron by means of lasers, analyzing qualitatively and quantitatively the consequences of the net charge of the particle. In our model, the coupling between the ion and the electromagnetic field includes the charge monopole and the internal dipole, within a multipolar expansion of the interaction Hamiltonian. Specifically, we perform a Power-Zienau-Woolley transformation, taking into account the motion of the center of mass. The net charge produces a correction in the atomic dipole which is of order $m_e/M$ with $m_e$ the electron mass and $M$ the total mass of the ion. With respect to neutral atoms, there is also an extra coupling to the laser field which can be approximated by that of the monopole located at the position of the center of mass. These additional effects, however, are shown to be very small compared to the dominant dipolar trapping term.