Light-Ion Trap (LIONTRAP), a high-precision Penning-trap mass spectrometer, was used to determine the atomic mass of 4He. Here, we report a 12 parts-per-trillion measurement of the mass of a 4He2+ ion, m(4He2+) = 4.001506179651(48) u. From this, the atomic mass of the neutral atom can be determined without loss of precision: m(4He) = 4.002603254653(48) u. This result is slightly more precise than the current CODATA18 literature value but deviates by 6.6 standard deviations. This is a post-peer-review, pre-copy edit version of an article published in PRL. The final version is available online at https://doi.org/10.1103/PhysRevLett.131.093201.
@article{arxiv.2311.04048,
title = {Penning-Trap Mass Measurement of Helium-4},
author = {Sangeetha Sasidharan and Olesia Bezrodnova and Sascha Rau and Wolfgang Quint and Sven Sturm and Klaus Blaum},
journal= {arXiv preprint arXiv:2311.04048},
year = {2023}
}