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Self-conjugate nuclei in the A ��� 70���80 region have attracted a great deal of attention due to phenomena such as shape coexistence and increasing collectivity along the N=Zline. We investigate the structure of nuclei in this region through lifetime measurements using the GRETINA array. The first implementation of the Differential Recoil Distance Doppler Shift technique with fast radioactive beams is demonstrated and verified through a measurement of the well-known B(E2; 2��������� 0������)transition strength in ������Kr. The method is then applied to determine the B(E2; 2��������� 0������) transition strength in ������Rb, the heaviest odd���odd N=Z nucleus for which this quantity has been determined. This result and extended systematics along N=Z suggest the dominance of the isoscalar part of the quadrupole transition strengths in self-conjugate nuclei, as well as the possible presence of shape coexistence in ������Rb.

Master Thesis report; The experimental arrangement of the n2EDM project, which aims at the measurement of the neutron electric dipole moment (dn), is inits construction phase. Currently, it is being evaluated for possible improvements that would lead to a greater ultra-cold neutron (UCN)counting efficiency and a larger sensitivity on the determination of dn.This work introduces a novel gaseous detector, which functioning is based on the absorption reaction n + 3He → 1H + 3H followed by theCF4 scintillation process. The counting capabilities for this detector are studied at two facilities that produce UCN from different mechanisms,one from spallation processes at the Paul Scherrer Institute (PSI), and the other from uranium fission at the TRIGA nuclear reactor in Mainz.Determination of parameters that optimize the UCN detection was also achieved, in particular, the gas pressure: 25 mbar for 3He and400 mbar for CF4. Pulse shape discrimination techniques allowed the background events identification, estimated in a 2% of the total countsat PSI. The absolute comparison against a cascade detector shows that the new prototype is doubly more efficient, that converts it in one ofthe most suitable alternatives for the UCN counting in the upcoming n2EDM experiment.

Transition probabilities of intermediate-spin yrast and non-yrast excitations in 80,82Se were investigated in a recoil distance Doppler-shift (RDDS) experiment performed at the Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro. The Cologne Plunger device for deep inelastic scattering was used for the RDDS technique and was combined with the AGATA Demonstrator array for the γ -ray detection and coupled to the PRISMA magnetic spectrometer for an event-by-event particle identification. In 80Se, the level lifetimes of the yrast (6+ 1 ) and (8+ 1 ) states and of a non-yrast band feeding the yrast 4+ 1 state are determined. A spin and parity assignment of the head of this sideband is discussed based on the experimental results and supported by large-scale shell-model calculations. In 82Se, the level lifetimes of the yrast 6+ 1 state and the yrare 4+ 2 state and lifetime limits of the yrast (10+ 1 ) state and of the 5− 1 state are determined. Although the experimental results contain large uncertainties, they are interpreted with care in terms of large-scale shell-model calculations using the effective interactions JUN45 and jj44b. The excited states’ wave functions are investigated and discussed with respect to the role of the neutron g9/2 orbital.

The lifetimes of the first excited 2+, 4+, and 6+ states in Zr98 were measured with the recoil-distance Doppler shift method in an experiment performed at GANIL. Excited states in Zr98 were populated using the fission reaction between a 6.2 MeV/u U238 beam and a Be9 target. The γ rays were detected with the EXOGAM array in correlation with the fission fragments identified by mass and atomic number in the VAMOS++ spectrometer. Our result shows a very small B(E2;21+→01+) value in Zr98, thereby confirming the very sudden onset of collectivity at N=60. The experimental results are compared to large-scale Monte Carlo shell model and beyond-mean-field calculations. The present results indicate the coexistence of two additional deformed shapes in this nucleus along with the spherical ground state. © 2018 American Physical Society.

WOS: 000439286800004, PubMed: 30085775, Energy differences between analogue states in the T = 1/2 Mg-23-Na-23 mirror nuclei have been measured along the rotational yrast bands. This allows us to search for effects arising from isospin-symmetrybreaking interactions (ISB) and/or shape changes. Data are interpreted in the shell model framework following the method successfully applied to nuclei in the f(7/2) shell. It is shown that the introduction of a schematic ISB interaction of the same type of that used in the f(7/2) shell is needed to reproduce the data. An alternative novel description, applied here for the first time, relies on the use of an effective interaction deduced from a realistic charge-dependent chiral nucleon-nucleon potential. This analysis provides two important results: (i) The mirror energy differences give direct insight into the nuclear skin; (ii) the skin changes along the rotational bands are strongly correlated with the difference between the neutron and proton occupations of the s(1/2) "halo" orbit., European Union [262010 ENSAR, FP7/2007-2013], The authors are grateful to the GANIL accelerator team. This work has been financed by the European Union Seventh Framework Program No. FP7/2007-2013 under Grant Agreement No. 262010 ENSAR.

The lifetimes of the first excited 2þ, 4þ, and 6þ states in 98Zr were measured with the recoil-distance Doppler shift method in an experiment performed at GANIL. Excited states in 98Zr were populated using the fission reaction between a 6.2 MeV=u 238U beam and a 9 Be target. The γ rays were detected with the EXOGAM array in correlation with the fission fragments identified by mass and atomic number in the VAMOS++ spectrometer. Our result shows a very small BðE2; 2þ 1 → 0þ 1 Þ value in 98Zr, thereby confirming the very sudden onset of collectivity at N ¼ 60. The experimental results are compared to large-scale Monte Carlo shell model and beyond-mean-field calculations. The present results indicate the coexistence of two additional deformed shapes in this nucleus along with the spherical ground state.

The high-spin structures and isomers of the N=81 isotones Xe135 and Ba137 are investigated after multinucleon-transfer (MNT) and fusion-evaporation reactions. Both nuclei are populated (i) in Xe136+U238 and (ii) Xe136+Pb208 MNT reactions employing the high-resolution Advanced Gamma Tracking Array (AGATA) coupled to the magnetic spectrometer PRISMA, (iii) in the Xe136+Pt198 MNT reaction employing the γ-ray array GAMMASPHERE in combination with the gas-detector array CHICO, and (iv) via a B11+Te130 fusion-evaporation reaction with the HORUS γ-ray array at the University of Cologne. The high-spin level schemesof Xe135 and Ba137 are considerably extended to higher energies. The 2058-keV (19/2-) state in Xe135 is identified as an isomer, closing a gap in the systematics along the N=81 isotones. Its half-life is measured to be 9.0(9) ns, corresponding to a reduced transition probability of B(E2,19/2-→15/2-)=0.52(6) W.u. The experimentally deduced reduced transition probabilities of the isomeric states are compared to shell-model predictions. Latest shell-model calculations reproduce the experimental findings generally well and provide guidance to the interpretation of the new levels.

The highly selective, intermediate-energy heavy-ion-induced neutron-pickup reaction, in combination with γ-ray spectroscopy using the γ-ray energy-tracking in-beam nuclear array (GRETINA), is shown to provide reliable relative spectroscopic strengths for high-ℓ orbitals in nuclei more neutron rich than the projectile. The reaction mechanism gives a significant final-state-spin alignment that is validated through γ-ray angular-distribution measurements enabled by the position sensitivity of GRETINA. This is the first time that γ-ray angular distributions could be extracted from a high-luminosity, fast-beam reaction other than inelastic scattering. This holds great promise for the restriction and assignment of Jπ quantum numbers in exotic nuclei. We advance this approach to study the crucial N=28 shell closure and extract the ratio g9/2:f5/2 of bound neutron single-particle strengths in Ca49, a benchmark for emerging multi-shell ab initio and configuration-interaction theories that are applicable along the Ca isotopic chain.

20th International School on Nuclear Physics, Neutron Physics and Applications -- SEP 16-22, 2013 -- Varna, BULGARIA, WOS: 000346180900050, An angular correlation experiment was carried out for S-33 at Laboratori Nazionali di Legnaro with the gamma-ray detector array GASP. The reaction used was Mg-24(N-14,alpha p)S-33 at a beam energy of 40MeV. An analysis of DCO ratios and triple gamma coincidences was performed. So far, a new level depopulated by 3 gamma -ray transitions has been found and its spin was determined. The work for further extension of the level scheme is in progress., Bulgarian Acad Sci, Inst Nucl Res & Nucl Energy, Bulgarian Nucl Regulatory Agcy, Joint Inst Nucl Res, Bogoliubov Lab Theoret Phys, Bulgarian Minist Educ Youth & Sci, Bulgarian Science Fund [DFNI-E01/2]; Bulgarian Ministry of Education and Science, This research has been supported by Bulgarian Science Fund under contract DFNI-E01/2 and by a NUPNET - NEDENSAA project funded by the Bulgarian Ministry of Education and Science.