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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.

Excited states of the neutron-rich nucleus 148 Ce have been populated by neutron-induced fission of 235 U and 241 Pu samples. Their electromagnetic decays were studied by means of γ-ray coincidence spectroscopy with fast-timing capabilities. Lifetimes of the 2 + 1 and 4 + 1 states of 148 Ce were obtained and their E2 decay rates deduced. The B 4/2 = B(E2; 4 + 1 → 2 + 1)/B(E2; 2 + 1 → 0 + 1) ratio indicates that 148 Ce is a transitional nucleus while the N = 88/90 shape phase transition evolves into a gradual change of nuclear deformation for proton numbers Z < 60.

High-spin states in [39Ce have been populated using the l30Te( l4C,5n) reaction. The level scheme has been extended to higher spins, including a new band of dipole transitions. The parity of several states has been changed from negative to positive, mainly based on the comparison with the level structure of the core nucleus l40Ce and the results of a realistic shell-model calculation. The dipole band is interpreted as a magnetic rotation band with tth]l/2

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