New Measurement of the Electron Magnetic Moment and the Fine Structure Constant

Abstract

A measurement using a one-electron quantum cyclotron gives the electron magnetic moment in Bohr magnetons, $g/2=1.00115965218073(28)$ [0.28 ppt], with an uncertainty 2.7 and 15 times smaller than for previous measurements in 2006 and 1987. The electron is used as a magnetometer to allow line shape statistics to accumulate, and its spontaneous emission rate determines the correction for its interaction with a cylindrical trap cavity. The new measurement and QED theory determine the fine structure constant, with ${\alpha }^{-1}=137.035999084(51)$ [0.37 ppb], and an uncertainty 20 times smaller than for any independent determination of $\alpha$.