Towards Collinear Laser Spectroscopy of Radioactive Molecules Utilizing In-trap Produced Molecular Ion Beam

TL;DR

This paper presents a new integrated method combining ion beam formation and collinear laser spectroscopy to study short-lived radioactive molecules, demonstrated with BaF+ ions, paving the way for future research on radioactive molecules like Ra.

Contribution

It introduces a novel combined approach for producing and spectroscopically analyzing radioactive molecules using in-trap ion reactions and laser techniques.

Findings

Successful production of BaF+ ions via in-trap reactions.

High-resolution spectroscopy of ^138BaF confirming vibrational and rotational structures.

Feasibility of studying short-lived radioactive molecules at ion beam facilities.

Abstract

Molecules containing short-lived isotopes, namely radioactive molecules, are among the most promising candidates for probing new physics beyond the Standard Model, although their production and spectroscopic measurements remain technically challenging. Here, we demonstrate an integrated methodology that combines formation of molecular ion beams in a radiofrequency quadrupole cooler-buncher with collinear laser spectroscopy. As a proof-of-principle experiment, we successfully produce molecular ions such as $\rm BaF^+$ and $\rm YbF^+$ via in-trap ion-molecule reactions and perform high-resolution laser spectroscopy of the target molecule $\rm ^{138}BaF$. Vibrational and rotational structures of $\rm ^{138}BaF$ across different electronic states are obtained using resonance-enhanced multiphoton ionization schemes, confirming the feasibility of the proposed methodology. This work establishes a practical route for future formation and spectroscopic studies of short-lived radioactive molecules, such as those containing $\rm ^{225}Ra$, at radioactive ion beam facilities.