Electron Rest Mass - Determination

Determination

The electron rest mass in kilograms is calculated from the definition of the Rydberg constant R_∞:

where α is the fine structure constant and h is the Planck constant. The relative uncertainty, 5×10−8 in the 2006 CODATA recommended value, is due entirely to the uncertainty in the value of the Planck constant.

The electron relative atomic mass can be measured directly in a Penning trap. It can also be inferred from the spectra of antiprotonic helium atoms (helium atoms where one of the electrons has been replaced by an antiproton) or from measurements of the electron g-factor in the hydrogenic ions 12C5+ or 16O7+. The 2006 CODATA recommended value has a relative uncertainty of 4.2×10−10.

The electron relative atomic mass is an adjusted parameter in the CODATA set of fundamental physical constants, while the electron rest mass in kilograms is calculated from the values of the Planck constant, the fine structure constant and the Rydberg constant. The correlation between the two values is negligible (r = 0.0003).