The mass ratios of charged particles, such as atomic and molecular ions, can be measured incredibly accurately in Penning traps. Some of the most accurate compa

The mass ratios of charged particles, such as atomic and molecular ions, can be measured incredibly accurately in Penning traps. Some of the most accurate comparisons are between the mass-3 ions ³He⁺, HD⁺, T⁺, and H₃⁺. Of these, only H₃⁺ has long-lived excited states, and the different excitation energies are clearly resolved in the mass comparisons [1]. The binding energies are much larger and have to be taken into account in the comparisons. [1] https://doi.org/10.1103/PhysRevLett.120.143002 https://doi.org/10.1103/PhysRevLett.120.143002