Oscillating nuclear electric dipole moments inside atoms

TL;DR

This paper explores how oscillating nuclear electric dipole moments induced by axion dark matter can cause detectable electronic transitions in atoms, proposing methods to observe these rare events and search for axions across various frequencies.

Contribution

It provides a detailed calculation of transition rates caused by axion-induced EDMs and discusses strategies to enhance signals for experimental detection.

Findings

Transition rate for 1 eV transition is about 10^(-22) per year per atom.

Detection requires macroscopic atomic samples due to low event rates.

Proposes methods to distinguish axion signals from background noise.

Abstract

Interaction with the axion dark matter (DM) field generates an oscillating nuclear electric dipole moment (EDM) with a frequency corresponding to the axion's Compton frequency. Within an atom, an oscillating EDM can drive electric dipole transitions in the electronic shell. In the absence of radiation, and if the axion frequency matches a dipole transition, it can promote the electron into the excited state. The excitation events can be detected, for example, via subsequent uorescence or photoionization. Here we calculate the rates of such transitions. For a single light atom and an axion Compton frequency resonant with a transition energy corresponding to 1 eV, the rate is on the order of 10^(-22) per year, so a macroscopic atomic sample would be needed. A fundamental challenge is discriminating against background processes that may lead to the excitation of the same electric dipole transition. The ways to enhance the signals to potentially observable levels exceeding backgrounds and to search for axions in an extended frequency range are discussed.