 <unk> of two of the stable isotopes of xenon , 129Xe and <unk> , have non @-@ zero intrinsic angular <unk> ( nuclear spins , suitable for nuclear magnetic resonance ) . The nuclear spins can be aligned beyond ordinary polarization levels by means of <unk> polarized light and <unk> vapor . The resulting spin polarization of xenon nuclei can surpass 50 % of its maximum possible value , greatly exceeding the thermal equilibrium value dictated by <unk> statistics ( typically 0 @.@ 001 % of the maximum value at room temperature , even in the strongest magnets ) . Such non @-@ equilibrium alignment of spins is a temporary condition , and is called <unk> . The process of <unk> the xenon is called optical pumping ( although the process is different from pumping a laser ) . 
