Magnetic Moment of the Proton in Bohr Magnetons

The magnetic moment of the proton has been measured by observing simultaneously an electronic and a nuclear magnetic transition in atomic hydrogen. Observations were made with a hydrogen maser operating in a 3500-G field. A theory is presented for the transient response of a three-level system under conditions of double resonance including effects of cavity pulling, spin-exchange collisions, and frequency shifts due to motional field narrowing. The electron-proton g-factor ratio in hydrogen is found to be gⱼ(H)gₚ(H)=μⱼ(H)μₚ(H)=-658.210706(6). This leads to a value of the proton moment in Bohr magnetons of μₚμB=1.521032181(15)×10^-3.