No abstract

Monoisotopic samples of exotic, neutron-rich 117 Rh nuclei, produced in the proton-induced fission of 238 U and separated using the IGISOL mass separator coupled to the JYFLTRAP Penning trap, were used to perform β and γ coincidence spectroscopy of 117 Pd. The spin parity of the ground state of 117 Pd was determined to be 1/2 + and the 19.1 ms isomer at 203.2 keV was assigned a spin-parity 7/2 − . The 117 Rh β − -decay scheme was considerably extended, and various sequences of the levels were interpreted as resulting from the prolate, oblate, and triaxial nuclear shapes. Some of the β − decays were considered as the allowed Gamow-Teller transitions. The experimental distribution of Gamow-Teller strength is discussed.

In the EXILL campaign a highly efficient array of high purity germanium (HPGe) detectors was operated at the cold neutron beam facility PF1B of the Institut Laue-Langevin (ILL) to carry out nuclear structure studies, via measurements of γ-rays following neutron-induced capture and fission reactions. The setup consisted of a collimation system producing a pencil beam with a thermal capture equivalent flux of about 108 n s−1cm−2 at the target position and negligible neutron halo. The target was surrounded by an array of eight to ten anti-Compton shielded EXOGAM Clover detectors, four to six anti-Compton shielded large coaxial GASP detectors and two standard Clover detectors. For a part of the campaign the array was combined with 16 LaBr3:(Ce) detectors from the FATIMA collaboration. The detectors were arranged in an array of rhombicuboctahedron geometry, providing the possibility to carry out very precise angular correlation and directional-polarization correlation measurements. The triggerless acquisition system allowed a signal collection rate of up to 6 × 105 Hz. The data allowed to set multi-fold coincidences to obtain decay schemes and in combination with the FATIMA array of LaBr3:(Ce) detectors to analyze half-lives of excited levels in the pico- to microsecond range. Precise energy and efficiency calibrations of EXILL were performed using standard calibration sources of 133Ba, 60Co and 152Eu as well as data from the reactions 27Al(n,γ)28Al and 35Cl(n,γ)36Cl in the energy range from 30 keV up to 10 MeV.