Progress at the WITCH experiment

The WITCH-experiment will measure the energy spectrum of the recoiling daughter ions in $\beta$-decay to search for non-standard scalar and tensor type interaction. To facilitate this a Penning trap is used to store the radioactive ions. Thus the recoil ions can leave the source without any energy loss and their energy can be probed by the subsequent retardation spectrometer. The experiment is being set up at present at ISOLDE/CERN. The principle and the status of the WITCH-experiment will be presented. (12 refs)

Nuclear Magnetic Moment of 59Cu with On-line β\beta-NMR on Oriented Nuclei

The nuclear magnetic moment of the nucleus 59Cu with one proton and two neutrons outside the closed N = Z = 28 shells, was measured in an on-line experiment combining beta-NMR with low temperature nuclear orientation and with particle detectors operating at a temperature of about 10K. From the data the center frequency \nu(B_ext = 0) = 209.51(22) MHz was derived. Using the hyperfine field of Cu in host iron from literature the results for the moment is \mu[59Cu] = +1.891(9)\mu_N, wich reveals a large deviation from the proton p3/2 single-particle value. This provides strong experimental evidence for a massive shell breaking at 56Ni