# Accurate optical measurement of nuclear polarization in optically pumped 3He gas

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Abstract : Large nuclear polarizations M over 80 % can now be achieved in gaseous 3He by optical pumping. The gas is excited by an RF discharge and is oriented using a high power LNA laser which is lamp pumped and tuned to the 2 3S-2 3P transition at 1.08 μm. In this paper we describe an experiment in which we measure M with high absolute precision. Our method is based on a change as a function of M in the ratio of σ or π polarized light absorbed from a weak probe beam by the 2 3S metastable atoms. The probe was delivered by a diode pumped LNA laser and propagated perpendicular to the direction of the magnetization. Simultaneous measurement of M was made by monitoring the degree of circular polarization $\cal{P}$ of the optical line at 668 nm emitted by the discharge. Our measurements show a linear relationship between M and $\cal{P}$ for all accessible M values and for a wide range of experimental conditions sample pressure, magnetic field, RF discharge level, etc

This provides a second method of measurement of the 3He nuclear polarization which is simple to operate and is calibrated and is calibrated over a pressure range of 0.15 to 6.5 torr.

Autor: N. Bigelow P. Nacher M. Leduc

Fuente: https://hal.archives-ouvertes.fr/

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