Comparison of the Rubidium-87 and Proton Zeeman Transition Frequencies in the Earth's Magnetic Field

Abstract

Alternate measurements of the earth's magnetic field have been made at the same location with a dc rubidium-87 magnetometer and with a proton free-precession magnetometer. The accuracy of the measurements is believed to be 1 μG in terms of the rubidium-87 frequency and 3 μG in terms of the proton frequency. The ratio of the $g$ factors for rubidium electrons and for protons in a spherical water sample is found to be 658.234±0.004. The rubidium electron $g$ factor is thus 27±6 parts per million higher than the $g$ factor for electrons in the hydrogen ground state.