Eine PrÄzisionsmessung des VerhÄltnisses der Spinresonanzfrequenz von Protonen zur Zyklotronfrequenz freier Elektronen im gleichen Magnetfeld

Abstract

A new precision measurement of the ratio of the proton NMR frequency to the cyclotron frequency of free electrons in the same magnetic field, Ω _p /Ω_e=γ _p mc/e, has been performed. A cyclotron resonance linewidth of 5 ppm only and a reduction of the large space charge shifts, amounting up to the order of 50 ppm in earlier published measurements, enabled a high accuracy. The final result is Ω _p /Ω _e =1.5209945×10⁻³±0.5 ppm, where the NMR is referred to a long cylindrical sample of H₂O, 0.2 m CuSO₄. Corrected to the free proton, we get Ω _p /Ω _e =1.5210329×10⁻³±0.6 ppm. Combination of our result with an EPR-measurement ofLambe yields a free electrong-factor ofg=2(1+(α/2π)−(0.30±0.09) (α/π)²) in good agreement with the theoretical valueg=2(1+(α/2π)−0.328(α/π)²±...).