H.H. Chen et al  claim that adding 4He to spin-exchange optical pumping (SEOP) cells confines 3He atoms to a diffusion-limited region, which effectively reduces the wall relaxation factor X. Here X is a phenomenological parameter used to characterize typical SEOP cells; it quantifies the observation that the measured linear slope of the relaxation rate with alkali density exceeds the spin-exchange rate. In addition they claim to demonstrate that magnetic field gradients cause a diffusive motion of 3He. We argue that these claims and other central conclusions drawn by the the authors of  are unjustified and/or unphysical. We also draw attention to several additional issues and shortcomings associated with the results, analysis, and presentation of data in  that confound clear interpretation."
Citation: Physical Review A
Pub Type: Journals
He3, He4, spin-exchange optical pumping