High-accuracy laser spectroscopy of $${{\bf{H}}}_{{\bf{2}}}^{{\boldsymbol{+}}}$$ and the proton–electron mass ratio

Details of the experiment

We use the same apparatus that we used in our previous work²⁰ to perform laser spectroscopy of an E2 transition in \({{\rm{H}}}_{2}^{+}\) and HD⁺. We prepare a cluster of trapped and sympathetically cooled molecular ions,…