Beta-decay of 27/2− isomers inN=83 nuclei

In theN=83 nucleus¹⁵¹Er we observed the isomericE3 transition in conversion electron measurements following on-line mass separation and located its 0.6 s 27/2^- isomer at 2.586 MeV. Gamma-ray data establish a 4.7(3)% Gamow-Tellerß-decay branch proceeding to high-spin states above 2 MeV excitation in¹⁵¹Ho. A weakß-decay branch of 0.7(3)% was also observed for the 0.5 s 27/2^- isomer in the¹⁴⁹Dy isotone, and it was established that a similar 27/2^-E3-isomer does not occur in¹⁵³Yb. First results on the¹⁵¹Tm and¹⁵¹Er ground-stateß-decays are briefly discussed.