Abstract

Nowadays, the determination of the fine structure constant relies on several measurements none of which lies within the traditional domain of atomic spectroscopy. The most accurate value for α is inferred from the electron’s magnetic anomaly, with an accuray of 4 ppb, by means of highly sophisticated QED calculations. The other determinations, all QED-independent, are obtained through the Josephson effect, the quantum Hall effect and the ratio h/M_o i.e. the Planck constant over the neutron’s mass: the accuracy of these measurements is a few parts in 10⁸. However, discrepancies in excess of 1 part in 10⁷ justify the need for clarifying measurements.

© 1998 IEEE