A Possible Nuclear Spin Dewar. Hyperfine Interactions of Short-Lived β Emitter 8Li and 12B in TiO2

It was confirmed by detecting the β-NMR of 12B (Iπ=1+, T1/2=20.2 ms) in a TiO2 (rutile) crystal that the nuclear spin polarization of 12B was totally maintained in the crystal as produced through a nuclear reaction before implantation. Two locations, site 1 and site 2, were found with the relative populations 9 and 1, respectively, and the electric field gradients (EFGs) at those sites were obtained to be q(site 1)=+(37.1±0.5)1015 V/cm2, η(site 1)<0.03, q(site 2)=+(185±5)1015 V/cm2 and η(site 2)=0.62±0.02. We also found that about 30% of the initial polarization of 8Li (Iπ=2+, T1/2=838 ms) was maintained in the crystal. Since the polarizations of other β emitting nuclei, 12,16N, 13,19O, and 41Sc were also totally maintained in the crystal, the crystal can be a 'Spin Dewar' in which many short-lived nuclides can be implanted with their polarizations totally maintained during their lifetimes for the studies not only on the electronic structure of impurities in it but also on the nuclear properties.