# The Roentgen interaction and forces on dipoles in time-modulated optical fields

## TL;DR

This paper investigates the often overlooked Roentgen interaction in atom-field dynamics, revealing its role in generating unexpected radiation forces and atomic accelerations in time-modulated optical fields.

## Contribution

It demonstrates how the Roentgen term causes differences between kinetic and canonical momentum, leading to novel radiation forces not previously characterized.

## Key findings

- Roentgen term causes forces against expected dipole forces
- Identifies accelerations perpendicular to beam propagation
- Highlights importance of the interaction in atomic dynamics

## Abstract

The Roentgen term is an often neglected contribution to the interaction between an atom and an electromagnetic field in the electric dipole approximation. In this work we discuss how this interaction term leads to a difference between the kinetic and canonical momentum of an atom which, in turn, leads to surprising radiation forces acting on the atom. We use a number of examples to explore the main features of this interaction, namely forces acting against the expected dipole force or accelerations perpendicular to the beam propagation axis.