# Charge-state distribution of Li ions from the $\beta$ decay of laser-trapped $^{6}$He atoms

## TL;DR

This study measures the charge state distribution of lithium ions produced from the beta decay of laser-trapped helium-6 atoms, providing experimental benchmarks to test and improve theoretical models of atomic final states post-decay.

## Contribution

The paper presents experimental measurements of Li ion charge states following helium-6 beta decay, highlighting discrepancies with existing theoretical calculations and previous experimental data.

## Key findings

- Significant differences between measured and theoretical charge state fractions.
- Discrepancies in energy dependence of charge distribution compared to prior measurements.
- Identification of potential reasons for the observed discrepancies.

## Abstract

Background: The accurate determination of atomic final states following nuclear $\beta$ decay plays an important role in many experiments. In particular, the charge state distributions of ions following nuclear $\beta$ decay are important for determinations of the $\beta-\nu$ angular correlation with improved precision. Purpose: Our measurement aims at providing benchmarks to test theoretical calculations. Method: The kinematics of Li$^{n+}$ ions produced following the $\beta$ decay of $^6{\rm He}$ within an electric field were measured using $^6{\rm He}$ atoms in the metastable $(1s2s,~{^3S_1})$ and in the $(1s2p,~{^3P_2})$ states confined by a magneto-optical trap. The electron shake-off probabilities were deduced including their dependence on ion energy. Results: We find significant discrepancies on the fractions of Li ions in the different charge states with respect to a recent calculation and discuss a plausible explanation. We also point out that there is no explanation for a large discrepancy between the same calculation and a previous measurement of the Li-ion energy dependence of the charge distribution from decays of the electronic ground state.