A low field determination of the proton gyromagnetic ratio in water

The proton gyromagnetic ratio in H/sub 2/O is measured by the low-field method. gamma '/sub p/(low)=2.67513376*10/sup 8/ s/sup -1/ T/sup -1/ (0.11 p.p.m.), leads to a value of the fine structure constant of alpha /sup -1/=137.0359840 (0.037 ppm) and a value for the quantized Hall resistance in SI units of R/sub H/=25812.80460 Omega (0.037 p.p.m.). To achieve this result, the dimensions of a 2.1-m solenoid were measured with an accuracy of 0.04 mu m, and the NMR (nuclear magnetic resonance) frequency of a water sample was measured in the field of the solenoid.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>