Knowledge of the electron mass has been improved by a factor of 13, thanks to a clever extension of previous Penning-trap experiments. A team from the Max-Planck-Institut für Kernphysik in Heidelberg, GSI and the ExtreMe Matter Institute in Darmstadt, and the Johannes Gutenberg-Universität in Mainz, used a Penning trap to measure the magnetic moment of an electron bound to a carbon nucleus in the hydrogen-like ion 12C5+. The cyclotron frequency of the combined system allowed precise determination of the magnetic field at the position of the electron, while the precession frequency allowed for measurement of the mass of the electron.
The result, in atomic-mass units, is 0.000548579909067(14)(9)(2) where the last error is theoretical. This new value for the electron’s mass value will allow comparison of the magnetic moment of the electron to theory – which is good to about 0.08 parts in 1012 – to better than one part in 1012.
Further reading
S Sturm et al. 2014 Nature 506 467.
