NMR CALIBRATION OF OPTICAL MEASUREMENT OF NUCLEAR-POLARIZATION IN HE-3

We have performed precise NMR measurements in order to calibrate a standard optical technique for measuring the polarization of He-3 nuclei. This optical technique requires knowledge of the pressure-dependent relationship between the nuclear polarization and the degree of circular polarization of the 668-nm light emitted from a He-3 discharge. We determined the nuclear polarization by comparing the adiabatic fast-passage NMR signal from samples of polarized He-3 at pressures between 0.1 and 5 torr to an identical sample of water. For water, the polarization is known from statistical mechanics. The He-3 is polarized using the metastability exchange technique for optical pumping of He-3. The accuracy of the calibration is +/-2%, which is required for applications in nuclear physics.