Study of the neutron-rich region in the vicinity of 208Pb via multinucleon transfer reactions

The multinucleon transfer reaction mechanism was employed to populate isotopes around the doubly- magic 208 Pb nucleus. We used an unstable 94 Rb beam on 208 Pb targets of different thickness. Transfer channels were studied via the fragment-γ and γ-γ coincidences, by using MINIBALL γ spectrometer coupled to a particle detector. Gamma transitions associated to the different Pb isotopes, populated by the neutron transfers, are discussed in terms of excitation energy and spin. Fragment angular distributions were extracted, andcompared with the reaction model

Search for 22^{22}Na in novae supported by a novel method for measuring femtosecond nuclear lifetimes

Classical novae are thermonuclear explosions in stellar binary systems, and important sources of $^{26}$Al and $^{22}$Na. While gamma rays from the decay of the former radioisotope have been observed throughout the Galaxy, $^{22}$Na remains untraceable. The half-life of $^{22}$Na (2.6 yr) would allow the observation of its 1.275 MeV gamma-ray line from a cosmic source. However, the prediction of such an observation requires good knowledge of the nuclear reactions involved in the production and destruction of this nucleus. The $^{22}$Na($p,\gamma$)$^{23}$Mg reaction remains the only source of large uncertainty about the amount of $^{22}$Na ejected. Its rate is dominated by a single resonance on the short-lived state at 7785.0(7) keV in $^{23}$Mg. In the present work, a combined analysis of particle-particle correlations and velocity-difference profiles is proposed to measure femtosecond nuclear lifetimes. The application of this novel method to the study of the $^{23}$Mg states, combining magnetic and highly-segmented tracking gamma-ray spectrometers, places strong limits on the amount of $^{22}$Na produced in novae, explains its non-observation to date in gamma rays (flux < 2.5x$10^{-4}$ ph/(cm$^2$s)), and constrains its detectability with future space-borne observatories.Comment: 18 pages, 3 figures, 1 tabl

Anomalies in the Charge Yields of Fission Fragments from the U(n,f)238 Reaction

Fast-neutron-induced fission of 238U at an energy just above the fission threshold is studied with a novel technique which involves the coupling of a high-efficiency γ-ray spectrometer (MINIBALL) to an inverse-kinematics neutron source (LICORNE) to extract charge yields of fission fragments via γ−γ coincidence spectroscopy. Experimental data and fission models are compared and found to be in reasonable agreement for many nuclei; however, significant discrepancies of up to 600% are observed, particularly for isotopes of Sn and Mo. This indicates that these models significantly overestimate the standard 1 fission mode and suggests that spherical shell effects in the nascent fission fragments are less important for low-energy fast-neutron-induced fission than for thermal neutron-induced fission. This has consequences for understanding and modeling the fission process, for experimental nuclear structure studies of the most neutron-rich nuclei, for future energy applications (e.g., Generation IV reactors which use fast-neutron spectra), and for the reactor antineutrino anomaly

Competition between Allowed and First-Forbidden beta Decay : The Case of Hg-208 -> Tl-2(0)8

The beta decay of Hg-208 into the one-proton hole, one neutron-particle Tl-208(81)127 nucleus was investigated at CERN-ISOLDE. Shell-model calculations describe well the level scheme deduced, validating the proton-neutron interactions used, with implications for the whole of the N > 126, Z 0(-)beta decay where the daughter state is core excited is unique, and can provide information on mesonic corrections of effective operators.Peer reviewe

Studies of exotic nuclei with advanced radiation detectors

Contemporary key nuclear physics questions are introduced. The role of radiation detection in the study of exotic nuclei is illustrated with examples related to NuSTAR at the FAIR facility. The discussed detection systems include: Si-tracker for light charged particle detection, the AGATA gamma-ray tracking detector, diamond detectors for heavy ion measurements, the AIDA implantation and decay detector, and the LaBr3(Ce) fast-timing array. Due to technology transfer, applications related to radiation physics are expected to benefit from these developments

Studies of exotic nuclei with advanced radiation detectors

Contemporary key nuclear physics questions are introduced. The role of radiation detection in the study of exotic nuclei is illustrated with examples related to NuSTAR at the FAIR facility. The discussed detection systems include: Si-tracker for light charged particle detection, the AGATA gamma-ray tracking detector, diamond detectors for heavy ion measurements, the AIDA implantation and decay detector, and the LaBr3(Ce) fast-timing array. Due to technology transfer, applications related to radiation physics are expected to benefit from these developments

100 years of nuclear isomers - then and now.

The suggestion that some atomic nuclei would be able to exist in more than one stable or metastable configuration was proposed by Soddy in 1917. Subsequently, the first experimental example of such an isomeric pair was reported by Hahn in 1921, in the form of two metastable states of 234Pa, then known as UZ and UX2. Nowadays, of the 3437 nuclides listed in the most recent NUBASE evaluation, 1318 have at least one metastable excited state with a half-life of 100 ns or longer. The present work reviews historical aspects of nuclear isomers, and the dfferent physical mechanisms that lead to their formation. Selected frontiers of contemporary isomer research are discussed, with an emphasis on remote regions of the nuclear landscape. Some possibilities for the electromagnetic manipulation of isomers are included

Fast Timing Measurement Using an LaBr3(Ce) Scintillator Detector Array Coupled with Gammasphere

A fast-timing experiment was performed at the Argonne National Laboratory in December 2015 and January 2016, measuring decay radiation of fission products from a 252Cf fission source. Details of the set-up, integration with Digital Gammasphere, and the data acquisition system are presented. The timing performance of the set-up, capable of measuring lifetimes from the nanosecond region down to tens of picoseconds, is discussed. First preliminary results from the fast-timing analysis of the fission fragment data are presente