Determination of the helium-4 mass in a Penning trap

Abstract:

We have measured the cyclotron frequencies of He⁺, H⁺ ₂ and D⁺ ₂ ions in a room temperature Penning trap. The resonances were detected destructively by a time-of-flight technique. The statistical uncertainty of the resonance frequencies was generally below 1 ppb. A detailed account of measures to minimize systematic frequency shift is presented. Using the accepted values for the proton and deuteron mass we obtain a value for the ⁴He mass: M(⁴ He) = 4.0026032489(22) (0.5 ppb). It is in agreement with the accepted value.