INTERMEDIATE-STATE REORIENTATION OF NUCLEI ALIGNED IN CERIUM DOUBLE NITRATE

Radiation patterns and linear polarization of gamma rays from decay of Co/sup 57/ and Ce/sup 141/aligned at low temperatures by Bleaney's method in cerium double nitrate were studied for evidence of intermediate-state reorientation in this crystal. Influence of spin-spin interactions should be negligible on theoretical grounds. Experimental results, expressed in terms of the mixing ratio delta = plus or minus (E2/M1)/sup 1/2/ for the M1 plus or minus E2 gamma transitions and of an attenuation coefficient Q/sub k/ in the angular distribution W( theta ) = SIGMA Q/sub k/A/sub k/P/sub k/ (cos theta ), are as follows: 123-kev gamma from Co/sup 57/ in Ce-Zn nitrate Y sites, delta = plus or minus 0.148 plus or minus 0.010, Q/sub 2/ =0.81 plus or minus 0.10 at 1/T/sup * 157; 145-kev gamma from Ce/sup 141/ in Ce-Mg nitrate, delta == plus or minus 0.085 plus or minus 0.013, Q/sub 2/ = 1.08 plus or minus 0.08 at 1/T/sup */ = 150. Comparisons are made with Steenberg's theory of intermediatestate reorientation by static, isotropic hfs coupling in the hard- core limit, and with results of other nuclear alignment experiments involving the same isotopes. (auth)