W. Zheng et al. [Phys. Rev. A 83, 061401(R) (2011)] measure under certain conditions a linear pressure dependence of the wall-induced nuclear relaxation rate of 3He in glass cells typically used to generate and/or store hyperpolarized 3He. Their interpretation is that this linear dependence is a general characteristic of paramagnetic wall relaxation, regardless of the relationship between the diffusion time tau_d across the cell and the longitudinal nuclear relaxation time T1. The authors'proposed modi¯cation of the polarization diffusion equation to account for this dependence cannot be valid for T1 >> tau_d, which holds for all of their measurements. Numerous previous studies support a broadly valid pressure-independent model for wall relaxation. The likely explanation for the linear dependence observed by the authors is diffusion through a capillary to a re¯lling valve that has a much higher probability per collision to relax 3He.
Citation: Physical Review A
Pub Type: Journals
3He, linear pressure dependence, nuclear relaxation