# Enhanced sensitivity for electron affinity measurements of rare elements

## TL;DR

A new technique improves sensitivity for measuring electron affinities, enabling precise measurements of rare and heavy elements.

## Contribution

A novel ion-trap method increases sensitivity by three orders of magnitude for electron affinity measurements.

## Key findings

- The EA of 35Cl was measured as 3.612720(44) eV with high precision.
- The method uses lower-power lasers to reduce uncertainties from laser bandwidth effects.
- The technique enables EA measurements for superheavy elements and isotopic studies.

## Abstract

The electron affinity (EA), the energy released when a neutral atom binds an additional electron, is a fundamental property of atoms that is governed by electron-electron correlations and is strongly related to an element’s chemical reactivity. However, conventional techniques for EA determination lack the experimental sensitivity to probe very scarce samples. As a result, the EA for the heaviest elements of the periodic table is entirely uncharted. Here, we present a novel technique to determine EAs through Laser Photodetachment Threshold Spectroscopy, performed in an electrostatic ion beam trap to increase the samples’ exposure to laser photons and, thus, improve the experimental signal sensitivity by three orders of magnitude. Moreover, the additional exposure time allows the use of lower-power continuous-wave narrow-band lasers that reduce uncertainties associated with broadening effects induced by the laser bandwidth. By applying this technique, we measure the EA of 35Cl to be 3.612720(44) eV, achieving state-of-the-art precision while employing five orders of magnitude fewer anions. The demonstrated sensitivity paves the way for systematic EA measurements across isotopic chains - including isotope shifts and hyperfine splittings - and ultimately for the first direct determination of electron affinities in superheavy elements.

Measuring the electron affinity, a fundamental chemical property, has been challenging for rare elements due to sensitivity limitations. Here, the authors present a novel ion-trap technique capable of performing high-precision affinity measurements with orders of magnitude fewer samples.