Trapping, cooling, and photodissociation analysis of state-selected H$\_2^+$ ions produced by (3+1) multiphoton ionization

TL;DR

This paper demonstrates the production and characterization of cold, state-selected H$_2^+$ ions via resonance-enhanced multi-photon ionization, with potential applications in high-resolution vibrational spectroscopy and fundamental metrology.

Contribution

It introduces a method to produce and verify high-purity, state-selected H$_2^+$ ions using REMPI and photodissociation techniques, advancing molecular ion control.

Findings

Successful production of cold, state-selected H$_2^+$ ions.

Verification of vibrational purity using UV photodissociation.

Differential photodissociation efficiencies enable vibrational transition detection.

Abstract

We report on the production of cold, state-selected H$_2^+$ molecular ions in a linear RF trap. The ions are produced by (3+1) resonance-enhanced multi-photon ionisation (REMPI) of H$_2$, and sympathetically cooled by laser-cooled Be$^+$ ions. After demonstrating and characterizing the REMPI process, we use photodissociation by a deep UV laser at 213~nm to verify the high vibrational purity of the produced H$_2^+$ ion samples. Moreover, the large difference between the photodissociation efficiencies of ions created in the $v=0$ and $v=1$ levels provides a way to detect a $v=0 \to 1$ transition. These results pave the way towards high-resolution vibrational spectroscopy of H$_2^+$ for fundamental metrology applications.