Tracking the ro-vibrational decay of single H₂⁺ ions using precision measurements of the H₂⁺/D⁺ cyclotron frequency ratio.

By re-developing the technique of simultaneous cyclotron frequency measurement of two ions in a Penning trap [1] with H₂⁺ and D⁺ we have achieved enough mass resolution to differentiate (using the mass-energy relation) between vibrational states of the H₂⁺ ion in a few hours of data taking. By repeated measurements over several weeks we have tracked the ro-vibrational decays of single H₂⁺ ions to the vibrational ground state and, in some cases, identified specific rotational levels. We hence aim to precisely correct the measured H₂⁺/D⁺ mass ratios for H₂⁺ rotational energy, which was a limitation in our previous measurement of the deuteron to proton mass ratio [2]. Details of the measurement and analysis will be presented.

[1] S. Rainville, J. K. Thompson and D. E. Pritchard, Science 303, 334 (2004).

[2] D. J. Fink and E.G. Myers, PRL 124, 013001 (2020).