Description
The Florida State University cryogenic Penning ion trap has previously produced the most precise values of the masses of heavier atoms required for several important atomic physics applications [1]. These include Rb and Cs for atom-interferometric measurement of h/m for the fine structure constant, and isotopes of Sr and Yb for King plot analyses. More recently we have focused on mass ratios between isotopes of hydrogen and helium. The relative masses of the proton, deuteron, triton and helion are fundamental constants impacting several areas of physics. In particular, a high-precision value for the mass difference between tritium and helium-3 is important for testing systematics in the ongoing KATRIN neutrino mass experiment, while the deuteron/proton mass ratio is important for interpreting the results of recent high-precision laser and terahertz spectroscopy of the HD+ molecular ion, leading to an improved value of the electron/proton mass ratio or, alternatively, limits on beyond-standard-model nucleon-nucleon interactions [2]. We achieve high precision by measuring the cyclotron frequency ratio of a pair of ions simultaneously trapped in a single Penning trap. For most of our measurements we alternate each ion between the center of the trap, where its cyclotron frequency is measured, and a large cyclotron “parking” orbit. Our previous measurements on mass-3 ions, besides providing the important Q-value for KATRIN, revealed significant errors in previously accepted values for the masses of p, d and h. In the case of measurements of H2+ against D+, we achieved sufficient resolution to distinguish different vibrational levels of H2+ by their difference in mass, and also to observe vibrational Stark quenching [3]. We then placed an H2+ and D+ in a coupled magnetron orbit and measured their cyclotron frequencies simultaneously [4]. This suppressed the effect of variation in the magnetic field by several orders of magnitude. It also reduced uncertainty related to measurement of the ions’ axial frequencies. Using this technique we partly resolved H2+ rotational energy through the change in mass. This resulted in a value for the deuteron/proton mass ratio at 5 ppt and the first proton atomic mass at 10 ppt.
[1] E.G. Myers, Int. J. Mass Spectrometry 349-350, 107 (2013).
[2] S. Patra, et al., Science, 369 (6508), 1238 (2020).
[3] D. J. Fink and E. G. Myers, Phys. Rev. Lett. 124, 013001 (2020)
[4] D. J. Fink and E. G. Myers, Phys. Rev. Lett. 127, 243001 (2021)
| Presenter name | Edmund Myers |
|---|---|
| How will you attend ICAP-27? | I am planning on in-person attendance |
