Addressing and manipulation of individual hyperfine states in cold trapped molecular ions and application to HD^{+} frequency metrology

TL;DR

This paper demonstrates for the first time precise manipulation of individual hyperfine states in a molecular ion, using advanced laser spectroscopy, enabling high-resolution measurements and testing molecular theory.

Contribution

It introduces a novel method for addressing and controlling hyperfine states in molecular ions, achieving unprecedented spectral resolution and enabling precise molecular tests.

Findings

First demonstration of hyperfine state manipulation in molecular ions

Achieved highest optical spectral resolution for a molecular ion

Performed the most precise test of ab-initio molecular theory

Abstract

Advanced techniques for manipulation of internal states, standard in atomic physics, are demonstrated for a charged molecular species for the first time. We address individual hyperfine states of ro-vibrational levels of a diatomic ion by optical excitation of individual hyperfine transitions, and achieve controlled transfer of population into a selected hyperfine state. We use molecular hydrogen ions (HD^{+}) as a model system and employ a novel frequency-comb-based, continuous-wave 5 \mum laser spectrometer. The achieved spectral resolution is the highest obtained so far in the optical domain on a molecular ion species. As a consequence, we are also able to perform the most precise test yet of the ab-initio theory of a molecule.