Detection of Single Ion Spectra by Coulomb Crystal Heating

TL;DR

This paper introduces sympathetic heating spectroscopy, a method that detects single ion spectra by observing fluorescence changes in a control ion caused by laser-induced heating of a spectroscopy ion, enabling detection of very weak signals.

Contribution

The paper presents a novel spectroscopy technique that links ion heating to fluorescence changes, allowing detection of optical transitions with minimal photon scattering.

Findings

Demonstrated technique using calcium isotopes

Detected optical transitions with very few scattered photons

Potential applications to molecular ion spectroscopy

Abstract

The coupled motion of ions in a radiofrequency trap has been used to connect the frequency- dependent laser-induced heating of a sympathetically cooled spectroscopy ion with changes in the fluorescence of a laser-cooled control ion. This technique, sympathetic heating spectroscopy, is demonstrated using two isotopes of calcium. In the experiment, a few scattered photons from the spectroscopy ion are transformed into a large deviation from the steady-state fluorescence of the control ion. This allows us to detect an optical transition where the number of scattered photons is below our fluorescence detection limit. Possible applications of the technique to molecular ion spectroscopy are briefly discussed.