Extended Data Fig. 1: Spin-exchange optical pumping.
From: Strong coupling of alkali-metal spins to noble-gas spins with an hour-long coherence time
Typical measurement of the pumping process of helium-3 by optically pumped potassium vapor. Here the potassium density is na = 4.9 ⋅ 1014 cm−3, and the helium depolarization time is \({T}_{1,{{{\rm{act}}}}}^{{{{\rm{b}}}}}=3.9\) h.
