Fluorescence Imaging of Individual Ions and Molecules in Pressurized Noble Gases for Barium Tagging in $^{136}$Xe

TL;DR

This paper demonstrates the selective imaging of individual Ba$^{2+}$ ions in high-pressure xenon gas, advancing barium tagging techniques for neutrinoless double beta decay detection and enabling studies of fluorescent molecules at solid-gas interfaces.

Contribution

It introduces a novel microscopy method for imaging single Ba$^{2+}$ ions in high-pressure xenon gas, crucial for background-free neutrino research and molecular photophysics.

Findings

Successful imaging of single Ba$^{2+}$ ions in 10 bar xenon gas.

Resolution achieved at the gas-solid interface using diffraction-limited system.

Potential for application in neutrinoless double beta decay searches.

Abstract

The imaging of individual Ba$^{2+}$ ions in high pressure xenon gas is one possible way to attain background-free sensitivity to neutrinoless double beta decay and hence establish the Majorana nature of the neutrino. In this paper we demonstrate selective single Ba$^{2+}$ ion imaging inside a high-pressure xenon gas environment. Ba$^{2+}$ ions chelated with molecular chemosensors are resolved at the gas-solid interface using a diffraction-limited imaging system with scan area of 1$\times$1~cm$^2$ located inside 10~bar of xenon gas. This new form of microscopy represents an important enabling step in the development of barium tagging for neutrinoless double beta decay searches in $^{136}$Xe, as well as a new tool for studying the photophysics of fluorescent molecules and chemosensors at the solid-gas interface.