Nuclear Alignment of Ce137m, Ce137, Ce139, Ce141, and Ce143

Abstract
Nuclei of Ce137m, Ce137, Ce139, Ce141, and Ce143 were aligned at low temperatures by the magnetic hyperfine-structure method. The angular distributions and the plane polarization of the emitted gamma radiation were measured as functions of temperature. For the spin sequence (Ce137m)112(M4,E5,255 keV)32(Ce137), the mixing ratio, |δ(E5M4)|, is less than 0.7. For the sequence (Ce137)32(iβ=0,1)32(M1,E2,445 keV)52, the magnetic moment of Ce137 is |μN|=0.90±0.15 nm and 2.6<δ(E2M1)<0.17. The spin of the 455-keV level of La137 is shown to be 32. For the sequence (Ce139)32(iβ=1)52(M1,E2,166 keV)72(La139), the magnetic moment of Ce139 is |μN|=0.95±0.20 nm and δ(E2M1)=+0.034±0.034. The 166-keV level of La139 has spin 52. For the sequence (Ce141)72(iβ=0)72(M1,E2,142 keV)52(Pr141), the magnetic moment of Ce141 is μN=1.30±0.20 nm and δ(E2M1)=+0.066±0.022. The spin of the 142-keV level of Pr141 is established as 72. The beta transition is predominantly iβ=0. For the sequence 72(Ce143)(iβ=0,1)52(72)(M1,E2,294 keV)52(72), the magnetic moment of Ce143 is |μN|=1.0±0.3 nm, and δ(E2M1)=0.80±0.20. The magnetic moments were found to be in agreement with configuration-mixing calculations. Evidence was found for two kinds of orientation attenuation in cerium magnesium nitrate.