Nuclear Spin Relaxation of Polycrystalline Xenon

Through spin exchange optical pumping it is possible to achieve upwards of nuclear spin polarization in Xe with an NMR signal enhancement of some orders of magnitude over typical thermal signals Hyperpolarized Xe has thus found application in several leading edge technologies At T and K the characteristic relaxation time of enriched polycrystalline Xe Xe Xe is well over hrs su cient for long term storage and transport Longitudinal nuclear spin relaxation of Xe at more convenient elds from to G is studied in detail Signi cant structure in relaxation times vs magnetic eld is seen the most prominent new nding being a sharp local long time T maximum of mins at G Such structure has not been observed in previous measurements of natural Xe Below temperatures of K relaxation can be attributed to cross relaxation with Xe mediated by spin di usion Measurements of Xe relaxation as a function of magnetic eld temperature and Xe isotopic content are reported and compared with expected theoretical behaviors It is seen that the characteristic nuclear spin relaxation of enriched Xe at K is nonexponential at these low elds For elds between G and G these nonexponential relaxation curves can be t well with a speci c spin di usion model Below G no such t is possible and thus quantum mechanical details of the coupling between Xe Xe and the bulk lattice are considered These ndings support the hypothesis that cross relaxation with Xe is indeed a dominant actor in the nuclear spin relaxation of polycrystalline Xe at such low elds and low temperatures To Iris my wife and friend and to my children Gary Jessica Daniel Anita and Nicolas who gave me the reason to carry on