High-precision evaluation of the magnetic moment of the helion

Abstract

NMR spectra of samples containing a mixture of hydrogen deuteride HD with pressure of about 80 atm and helium-3 with partial pressure of about 1 atm are analyzed. The ratio of the resonance frequencies of the nuclei, F(³He)/F(H₂), is determined to be 0.761786594(2), which is equal to the magnetic moment of the helion (bound in a helium atom) in the units of the magnetic moment of a proton (bound in molecular hydrogen). The uncertainty of two digits in the last place corresponds to a relative error of δ[F(³He)/F(H₂)] = 2.6 × 10⁻⁹. The use of the known calculated data on the shielding of nuclei in the helium-3 atom (σ(³He) = 59924(2) × 10⁻⁹) and on the shielding of protons in hydrogen (σ(H₂) = 26288(2) × 10⁻⁹) yields a value of μ(³He)/μ _p = −0.761812217(3) for the free magnetic moment of the helion in the units of the proton magnetic moment.