BETA-DECAY-INDUCED LATTICE SITE CHANGE IN THE DECAY NB-90 ]ZR-90 IN FE

We report the observation of a beta-decay-induced lattice site change after the decay of Nb-90 (T1/2=14.6 h) to Zr-90 in Fe. Samples of (NbF e)-Nb-90 were prepared by recoil implantation and cooled to temperatur es of approximately 10 mK. The lattice location before and after the b eta decay was monitored via nuclear magnetic resonance on oriented nuc lei (NMR-ON) on Nb-90 and Zr-90m (T1/2=0.8 s), respectively. With doub le-resonance NMR-ON measurements it could be shown that for a fraction of approximately 0.14(3) of Zr-90m a beta-decay-induced lattice site change must have occurred.