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Lifetimes or lifetime limits of a small number of excited states of the sulfur isotopes with mass numbers A=35, 36, 37, and 38 have been measured using the differential recoil-distance method. The isotopes of sulfur were populated in binary grazing reactions initiated by a beam of 36S ions of energy 225 MeV incident on a thin 208Pb target which was mounted in the Cologne plunger apparatus. The combination of the PRISMA magnetic spectrometer and an early implementation of the AGATA γ-ray tracking array was used to detect γ rays in coincidence with projectile-like nuclear species. Lifetime measurements of populated states were measured within the range from about 1 to 100 ps. The number of states for which lifetime measurements or lifetime limits were possible was limited by statistics. For 35S, the lifetime was determined for the first 1/2+ state at 1572 keV ; the result is compared with a previous published lifetime value. The lifetime of the 3− state of 36S at 4193 keV was determined and compared with earlier measurements. No previous lifetime information exists for the (6+) state at 6690 keV ; a lifetime measurement with large associated error was made in the present work. For 37S, the states for which lifetime limits were established were those at 646 keV with Jπ=3/2− and at 2776 keV with Jπ=11/2− ; there are no previously published lifetime values for excited states of 37S. Finally, a lifetime limit was established for the Jπ=(6+) state of 38S at 3675 keV ; no lifetime information exists for this state in the literature. Measured lifetime values were compared with the results of state-of-the-art shell-model calculations based on the PSDPF, SDPF-U, and FSU effective interactions. In addition, nuclear magnetic-dipole and electric-quadrupole moments, branching ratios, mixing ratios, and electromagnetic transition rates, where available, have been compared with shell-model values. The current work suffers from poor statistics ; nevertheless, lifetime values and limits have been possible, allowing a useful discussion of the ability of state-of-the-art shell-model calculations to reproduce the experimental results.

Discovering unexplored high-spin states in neutron-rich nuclei can open up a new direction to study band structure and the associated shell structure in isospin-asymmetric many-body systems. However, experimental reach has so far been limited to neutron-deficient or stable nuclei which are preferentially produced in fusion reactions used in such studies. Here, we report the first γ-ray spectroscopy with fusion reactions using a reaccelerated rare-isotope beam of 45K performed at the ReA3 facility of the National Superconducting Cyclotron Laboratory. Using particle and γ-ray coincidence techniques, three new higher-lying states around 6 MeV and five new γ-ray transitions were identified for 46Ca, suggesting three independent band structures formed from different particle-hole configurations. The rotational-like band built on the 0+2 state is established up to the tentatively assigned 6+2 state. New results are compared to large-scale shell model calculations, confirming the validity of the effective interaction describing particle-hole excitations across the Z=20 and N=28 shell gaps in the vicinity of doubly magic 48Ca.

Background: The heaviest Tz=0 doubly-magic nucleus, 100Sn, and the neighboring nuclei offer unique opportunities to investigate the properties of nuclear interaction. For instance, the structure of light-Sn nuclei has been shown to be affected by the delicate balance between nuclear-interaction components, such as pairing and quadrupole correlations. From Cd to Te, many common features and phenomena have been observed experimentally along the isotopic chains, leading to theoretical studies devoted to a more general and comprehensive study of the region. In this context, having only two proton holes in the Z=50 shell, the Cd isotopes are expected to present properties similar to those found in the Sn isotopic chain. Purpose: The aim of this work was to measure lifetimes of excited states in neutron-deficient nuclei in the vicinity of 100Sn. Methods: The neutron-deficient nuclei in the N≈Z≈50 region were populated using a multinucleon transfer reaction with a 106Cd beam and a 92Mo target. The beamlike products were identified by the VAMOS++ spectrometer, while the γ rays were detected using the AGATA array. Lifetimes of excited states were determined using the recoil distance Doppler-shift method, employing the Cologne differential plunger. Results: Lifetimes of low-lying states were measured in the even-mass 102–108Cd isotopes. In particular, multiple states with excitation energy up to ≈3 MeV, belonging to various bands, were populated in 106Cd via inelastic scattering. The transition strengths corresponding to the measured lifetimes were compared with those resulting from state-of-the-art beyond-mean-field calculations using the symmetry-conserving configuration-mixing approach. Conclusions: Despite the similarities in the electromagnetic properties of the low-lying states, there is a fundamental structural difference between the ground-state bands in the Z=48 and Z=50 isotopes. The comparison between experimental and theoretical results revealed a rotational character of the Cd nuclei, which have prolate-deformed ground states with β2≈0.2. At this deformation Z=48 becomes a closed-shell configuration, which is favored with respect to the spherical one.

Two nucleon transfer reactions at low bombarding energies are an ideal tool to investigate nucleon-nucleon correlations. With heavy ions one has the possibility to transfer several nucleon pairs, involving both neutrons and protons at the same time. In this work we will study how pair correlations can be probed in heavy ion collisions , and how the strong Coulomb field influences the reaction dynamic.

The shape and collectivity of 106Cd was investigated via a sub-barrier-energy Coulomb excitation experiment performed at the National Superconducting Cyclotron Laboratory Re-accelerator facility using the JANUS setup. Transition matrix elements between low-lying states were found to agree with adopted values, and information on the shape and collectivity of higher-lying states was extracted for the first time. Locally optimized large-scale shell-model calculations were found to describe well the B(E2) transition strengths but failed to reproduce the spectroscopic quadrupole moments Qs. An analysis of the E2 rotational invariants and the normalized quadrupole moment qs indicates that this may be due to a significant degree of triaxiality in 106Cd which is not captured by the present shell-model calculations. Analogous calculations for the Fe isotopes (two protons below the Z=28 magic number) reveal the critical role of high-j neutron configurations for the description of quadrupole moments in the heavy Fe and Cd isotopes (two protons below magic Z=50), but this effect is insufficient to explain the shape of 106Cd, posing a puzzle for the understanding of nuclear structure towards N=50.

The high-spin structures of Ba-136 and Ba-137 are investigated after multinucleon-transfer (MNT) and fusion-evaporation reactions. Ba-136 is populated in a Xe-136 + U-238 MNT reaction employing the high-resolution Advanced GAmma Tracking Array (AGATA) coupled to the magnetic spectrometer PRISMA at the Laboratori Nazionali di Legnaro, Italy, and in two Be-9 + Te-130 fusion-evaporation reactions using the High-efficiency Observatory for gamma-Ray Unique Spectroscopy (HORUS) at the FN tandem accelerator of the University of Cologne, Germany. Furthermore, both isotopes are populated in an elusive reaction channel in the B-11 + Te-130 fusion-evaporation reaction utilizing the HORUS gamma-ray array. The level scheme above the J(pi) = 10(+) isomer in Ba-136 is revised and extended up to an excitation energy of approximately 5.5 MeV. From the results of angular-correlation measurements, the E-x = 3707- and E-x = 4920-keV states are identified as the bandheads of positive- and negative-parity cascades. While the high-spin regimes of both Te-132 and Xe-134 are characterized by high-energy 12(+) -> 10(+) transitions, the Ba-136 E2 ground-state band is interrupted by negative-parity states only a few hundred keV above the J(pi) = 10(+) isomer. Furthermore, spins are established for several hitherto unassigned high-spin states in Ba-137. The new results close a gap along the high-spin structure of N < 82 Ba isotopes. Experimental results are compared to large-scale shell-model calculations employing the GCN50:82, Realistic SM, PQM130, and SN100PN interactions. The calculations suggest that the bandheads of the positive-parity bands in both isotopes are predominantly of proton character.

Lifetimes of excited states of the phosphorus isotopes 33 , 34 , 35 , 36 15 P have been measured by using the differential recoil-distance method. The isotopes of phosphorus were populated in binary grazing reactions initiated by a beam of 36 S ions of energy 225 MeV incident on a thin 208 Pb target mounted in the Cologne plunger apparatus. The combination of the PRISMA magnetic spectrometer and an early implementation of the AGATA γ -ray tracking array was used to detect γ rays in coincidence with projectile-like nuclear species. Lifetime measurements of populated states were made within the range from about 1 to 100 ps. The number of states for which lifetime measurements were possible was limited by statistics. For 33 P , lifetime limits were determined for the first 3/2+ and 5/2+ states at 1431 and 1848 keV, respectively; the results are compared with previous published lifetime values. The lifetime of the first 2+ state of 34 P at 429 keV was determined and compared with earlier measurements. For 35 P , the states for which lifetimes, or lifetime limits, were determined were those at 2386, 3860, 4101, and 4493 keV, with Jπ values of 3/2+, 5/2+, 7/2− 1 , and 7/2− 2 , respectively. There have been no previous published lifetimes for states in this nucleus. A lifetime was measured for the stretched π ( 1 f 7 / 2 ) ⊗ ν ( 1 f 7 / 2 ) J π = ( 7 + ) state of 36 P at 5212 keV and a lifetime limit was established for the stretched π ( 1 d 3 / 2 ) ⊗ ν ( 1 f 7 / 2 ) J π = ( 5 − ) state at 2030 keV. There are no previously published lifetimes for states of 36 P . Measured lifetime values were compared with the results of state-of-the-art shell-model calculations based on the PSDPF effective interaction. In addition, measured branching ratios, published mixing ratios, and electromagnetic transition rates, where available, have been compared with shell-model values. In general, there is good agreement between experiment and the shell model; however there is evidence that the shell-model values of the M1 transition rates for the 3/2+1→ 1 / 2 + (ground state) and 5/2+1→ 3 / 2 + 1 transitions in 33 P underestimate the experimental values by a factor between 5 and 10. In 35 P there are some disagreements between experimental and shell-model values of branching ratios for the first and second excited 7/2− states. In particular, there is a serious disagreement for the decay characteristics of the second 7/2− state at 4493 keV, for which the shell-model counterpart lies at 4754 keV. In this case, the shell-model competing electromagnetic decay branches are dominated by E1 and M1 transitions.

Detailed information on isomeric states in A approximate to 135 nuclei is exploited to shell-model calculations in the region northwest of doubly magic nucleus Sn-132. The N = 79 isotones Xe-133 and Ba-135 are studied after multinucleon transfer in the Xe-136 + Pb- 208 reaction employing the high-resolution Advanced GAmma Array (AGATA) coupled to the magnetic spectrometer PRISMA at the Laboratori Nazionali di Legnaro, Italy and in a pulsed- beam experiment at the FN tandem accelerator of the University of Cologne Germany utilizing a Be-9 + Te-130 fusion-evaporation reaction at a beam energy of 40 MeV. Isomeric states are identified via delayed gamma-ray spectroscopy. Hitherto tentative excitation energy spin and parity assignments of the 2017-keV J(pi) = 23/2(+) isomer in Xe-133 are confirmed and a half-life of T-1/2 = 8.64(13) ms is measured. The 2388-keV state in Ba-135. is identified as a J(pi) = 23/2(+) isomer with a half-life of 1.06(4) ms. The new results show a smooth onset of isomeric J(pi) = 23/2(+) states along the N = 79 isotones and close a gap in the high-spin systematics towards the recently investigated J(pi) = 23/2(+) isomer in Nd-139. The resulting systematics of M2 reduced transition probabilities is discussed within the of the nuclear shell model. Latest large-scale shell- model calculations employing the SN100PN, GCN50:82, SN100-KTH and a realistic effective interaction reproduce the experimental findings generally well and give insight into the structure of the isomers.

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.

Pair correlations have been investigated in heavy-ion collisions via studies of the transfers of different nucleon pairs. In particular, excitation functions of one- and two-neutron transfer channels have been measured for the closed shell 40Ca + 96Zr and superfluid 60Ni + 116Sn systems from the Coulomb barrier energy to energies far below. By using the unique performance of the magnetic spectrometer PRISMA, in terms of resolution and efficiency, measurements at very low bombarding energies have been performed. The experimental transfer probabilities have been compared with semiclassical microscopic calculations that incorporate nucleonnucleon correlations, together with known structure information of entrance and exit channels nuclei and reaction dynamics. These calculations well reproduce, in the whole energy range, one- and two-neutron transfer channels in shape and magnitude.

Background: The fusion reaction 12C+30Si is a link between heavier cases studied in recent years, and the light heavy-ion systems, e.g., 12C+12C, 16O+16O that have a prominent role in the dynamics of stellar evolution. 12C+30Si fusion itself is not a relevant process for astrophysics, but it is important to establish its behavior below the barrier, where couplings to low-lying collective modes and the hindrance phenomenon may determine the cross sections. The excitation function is presently completely unknown below the barrier for the 12C+30Si reaction, thus no reliable extrapolation into the astrophysical regime for the C+C and O+O cases can be performed. Purpose: Our aim was to carry out a complete measurement of the fusion excitation function of 12C+30Si from well below to above the Coulomb barrier, so as to clear up the consequence of couplings to low-lying states of 30Si, and whether the hindrance effect appears in this relatively light system which has a positive Q value for fusion. This would have consequences for the extrapolated behavior to even lighter systems. Methods: The inverse kinematics was used by sending 30Si beams delivered from the XTU Tandem accelerator of INFN-Laboratori Nazionali di Legnaro onto thin 12C (50μg/cm2) targets enriched to 99.9% in mass 12. The fusion evaporation residues (ER) were detected at very forward angles, following beam separation by means of an electrostatic deflector. Angular distributions of ER were measured at Ebeam=45, 59, and 80 MeV, and they were angle integrated to derive total fusion cross sections. Results: The fusion excitation function of 12C+30Si was measured with high statistical accuracy, covering more than five orders of magnitude down to a lowest cross section ≃3μb. The logarithmic slope and the S factor have been extracted and we have convincing phenomenological evidence of the hindrance effect. These results have been compared with the calculations performed within the model that considers a damping of the coupling strength well inside the Coulomb barrier. Conclusions: The experimental data are consistent with the coupled-channels calculations. A better fit is obtained by using the Yukawa-plus-exponential potential and a damping of the coupling strengths inside the barrier. The degree of hindrance is much smaller than the one in heavier systems. Also a phenomenological estimate reproduces quite closely the hindrance threshold for 12C+30Si, so that an extrapolation to the C+C and O+O cases can be reliably performed.

International audience; We studied multinucleon transfer reactions in the Au197+Te130 system at Elab=1.07 GeV by employing the PRISMA magnetic spectrometer coupled to a coincident detector. For each light fragment we constructed, in coincidence, the distribution in mass of the heavy partner of the reaction. With a Monte Carlo method, starting from the binary character of the reaction, we simulated the de-excitation process of the produced heavy fragments to be able to understand their final mass distribution. The total cross sections for pure neutron transfer channels have also been extracted and compared with calculations performed with the grazing code.

The transitional nucleus 131Xe is investigated after multinucleon transfer in the 136Xe + 208Pb and 136Xe + 238U reactions employing the high-resolution Advanced γ -Tracking Array (AGATA) coupled to the magnetic spectrometer PRISMA at the Laboratori Nazionali di Legnaro, Italy, and as an elusive reaction product in the fusion-evaporation reaction 124Sn(11B,p3n) 131Xe employing the High-efficiency Observatory for γ -Ray Unique Spectroscopy (HORUS) γ -ray array coupled to a double-sided silicon strip detector at the University of Cologne, Germany. The level scheme of 131Xe is extended to 5 MeV. A pronounced backbending is observed at hω¯ ≈ 0.4 MeV along the negative-parity one-quasiparticle νh11/2(α = −1/2) band. The results are compared to the high-spin systematics of the Z = 54 isotopes and the N = 77 isotones. Large-scale shell-model calculations employing the PQM130, SN100PN, GCN50:82, SN100-KTH, and a realistic effective interaction reproduce the experimental findings and provide guidance to elucidate the structure of the high-spin states. Further calculations in 129−132Xe provide insight into the changing nuclear structure along the Xe chain towards the N = 82 shell closure. Proton occupancy in the π 0h11/2 orbital is found to be decisive for the description of the observed backbending phenomenon.

Charge state distributions of the Ra recoil ions produced in the 12C+Pb fusion-evaporation reactions have been obtained by measuring their yields as a function of the high voltage applied to an electrostatic deflector. Well-defined two-humped yield curves for evaporation residues (ERs) were observed. Such observations can be explained by the different sets of charge states inherent in Ra recoil ions. These charge sets correspond to the equilibrated and nonequilibrated components, as earlier observed for evaporation residues produced in different reactions. The main parameters of the distributions (mean charge values, widths, and relative intensities) for both components have been estimated using Monte Carlo simulations of the transmission of the Ra recoil ions through the deflector. For the equilibrated component the values of the mean charge and width are close to those given by different empirical systematics. For the nonequilibrated component these parameters have been obtained for the first time. The additional nonequilibrated ionization is presumably due to the formation of inner shell vacancies produced by the internal conversion of nuclear isomeric transitions of ERs. Nonequilibrated charge parameters obtained for Ra recoil ions are compared to similar available experimental data and some theoretical predictions.

Angular distributions of γ-rays for selected transitions in 40, 41, 42Ar isotopes have been studied with the PRISMA magnetic spectrometer coupled to the CLARA γ array. These transitions were populated in Ar isotopes reached via neutron transfer in the 40Ar + 208Pb reaction. By comparison with the shape of the experimental angular distribution of the known E2 transitions we established more firmly the spin and parity of excited states. In particular, in 41Ar for the (11/2-) state through the (11/2-) -> 7/2- transition whose structure was discussed in terms of a phonon-fermion coupled state. The comparison with the expected fully aligned spin indicated that a high level of spin alignment has been reached.

Learning how 19F is produced and destructed in AGB-stars is crucial. Fluorine abundance is in fact important, given that it is strongly tied to standard and extra-mixing processes taking place in AGB-stars. This kind of objects are considered to be the main sources of fluorine in galactic environment, in which experimental abundances are far overestimated. For this reason the reaction 19F(α, p)22Ne, that represents the main destruction channel in He-rich environment, was studied at energies corresponding to T~2·10^8 K.

The high-spin structures and isomers of the N = 81 isotones 135Xe and 137Ba are investigated after multinucleon-transfer (MNT) and fusion-evaporation reactions. Both nuclei are populated (i) in 136Xe+238U and (ii) 136Xe+208Pb MNT reactions employing the high-resolution Advanced Gamma Tracking Array (AGATA) coupled to the magnetic spectrometer PRISMA, (iii) in the 136Xe+198Pt MNT reaction employing the γ -ray array GAMMASPHERE in combination with the gas-detector array CHICO, and (iv) via a 11B+130Te fusion-evaporation reaction with the HORUS γ -ray array at the University of Cologne. The high-spin level schemes of 135Xe and 137Ba are considerably extended to higher energies. The 2058-keV (19/2−) state in 135Xe 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.

Background: While the N = 50 shell-gap evolution towards 78Ni is presently in the focus of nuclear structure research, experimental information on the neutron effective single-particle energy sequence above the 78Ni core remain scarce. Direct nucleon-exchange reactions are indeed difficult with presently available post-accelerated radioactive-ion beams (especially for high orbital-momentum orbitals) in this exotic region. Purpose: In this study we probe the evolution of the ν(g7/2) effective single-particle energy which is a key to understanding the possible evolution of the spin-orbit splitting due to the proton-neutron interaction in the 78Ni region. To achieve this goal, a method based on lifetime measurements is used for the first time. The obtained lifetimes of the 7/2+ states in 87Kr and 85Se are used to investigate the ν(g7/2) evolution. Method: Yrast and near-yrast states in the light N = 51 isotones 85Se and 87Kr were populated via multinucleon transfer reactions, using a 82Se beam and a 238U target at the LNL tandem-ALPI facility. The prompt γ rays were detected by the AGATA Demonstrator and particle identification was performed using the PRISMA spectrometer. Lifetime measurements were performed by using the Cologne plunger device for deep inelastic reactions and the Recoil Distance Doppler Shift technique. Results: We obtain τ(7/2+)= 0.4(+1.6, −0.4) ps for 87Kr. In the case of 85Se an upper limit of 3(2) ps is obtained for the τ(7/2+) value. Conclusion: For 87Kr, the measured (7/2+) lifetime is consistent with a core-coupled 2+ ⊗ ν(d5/2) configuration for this state. This result is consistent with that obtained by direct reaction, which validates our method. For 85Se, the measured 7/2+ lifetime limit indicates a very small contribution of the ν(g7/2) configuration to the wave function of this state.

We measured multinucleon transfer reactions in the 40Ar+208Pb system at an energy close to the Coulomb barrier, by employing the PRISMA magnetic spectrometer. We extracted differential and total cross sections of the different transfer channels, with a careful investigation of the total kinetic energy loss distributions. A comparison between different systems having the same 208Pb target and with projectiles going from neutron-poor to neutron-rich nuclei, i.e., 40Ca, 58Ni, and 40Ar, as well as between the data and GRAZING calculations have been carried out. The neutron-rich (stable) 40Ar beam allowed us to get access to the channels involving proton pick-up, whose behaviour in connection with the production of neutron-rich heavy partner has been outlined.

We performed a gamma-particle coincidence experiment for the 60Ni+116Sn system in order to investigate whether the population of the two-neutron pick-up channel leading to 62Ni is mainly concentrated in the ground state transition, as has been found in a previous work. The experiment has been performed by employing the PRISMA magnetic spectrometer coupled to the Advanced Gamma Tracking Array (AGATA) demonstrator. The strength distribution of excited states corresponding to the inelastic, one- and two-neutron transfer channels has been extracted. We found that in the two-neutron transfer channel the strength to excited states corresponds to a fraction (less than 24%) of the total, consistent with the previously obtained results that the 2n channel is dominated by the ground to ground state transition.

Background: Multinucleon transfer reactions (MNT) are a competitive tool to populate exotic neutron-rich nuclei in a wide region of nuclei, where other production methods have severe limitations or cannot be used at all. Purpose: Experimental information on the yields of MNT reactions in comparison with theoretical calculations are necessary to make predictions for the production of neutron-rich heavy nuclei. It is crucial to determine the fraction of MNT reaction products which are surviving neutron emission or fission at the high excitation energy after the nucleon exchange. Method: Multinucleon transfer reactions in 136Xe+238U have been measured in a high-resolution γ-ray/particle coincidence experiment. The large solid-angle magnetic spectrometer PRISMA coupled to the high-resolution Advanced Gamma Tracking Array (AGATA) has been employed. Beamlike reaction products after multinucleon transfer in the Xe region were identified and selected with the PRISMA spectrometer. Coincident particles were tagged by multichannel plate detectors placed at the grazing angle of the targetlike recoils inside the scattering chamber. Results: Mass yields have been extracted and compared with calculations based on the grazing model for MNT reactions. Kinematic coincidences between the binary reaction products, i.e., beamlike and targetlike nuclei, were exploited to obtain population yields for nuclei in the actinide region and compared to x-ray yields measured by AGATA. Conclusions: No sizable yield of actinide nuclei beyond Z=93 is found to perform nuclear structure investigations. In-beam γ-ray spectroscopy is feasible for few-neutron transfer channels in U and the −2p channel populating Th isotopes. Background: Multinucleon transfer reactions (MNT) are a competitive tool to populate exotic neutron-rich nuclei in a wide region of nuclei, where other production methods have severe limitations or cannot be used at all. Purpose: Experimental information on the yields of MNT reactions in comparison with theoretical calculations are necessary to make predictions for the production of neutron-rich heavy nuclei. It is crucial to determine the fraction of MNT reaction products which are surviving neutron emission or fission at the high excitation energy after the nucleon exchange. Method: Multinucleon transfer reactions in 136Xe+238U have been measured in a high-resolution γ-ray/particle coincidence experiment. The large solid-angle magnetic spectrometer PRISMA coupled to the high-resolution Advanced Gamma Tracking Array (AGATA) has been employed. Beamlike reaction products after multinucleon transfer in the Xe region were identified and selected with the PRISMA spectrometer. Coincident particles were tagged by multichannel plate detectors placed at the grazing angle of the targetlike recoils inside the scattering chamber. Results: Mass yields have been extracted and compared with calculations based on the grazing model for MNT reactions. Kinematic coincidences between the binary reaction products, i.e., beamlike and targetlike nuclei, were exploited to obtain population yields for nuclei in the actinide region and compared to x-ray yields measured by AGATA. Conclusions: No sizable yield of actinide nuclei beyond Z=93 is found to perform nuclear structure investigations. In-beam γ-ray spectroscopy is feasible for few-neutron transfer channels in U and the −2p channel populating Th isotopes.

International audience; The level structure of the neutron-rich 69Cu, 71Cu, and 73Cu isotopes has been investigated by means ofmultinucleon transfer reactions. The experiment was performed at Laboratori Nazionali di Legnaro using theAGATA Demonstrator array coupled to the PRISMA magnetic spectrometer. Lifetimes of excited states inCu nuclei were measured with the recoil-distance Doppler-shift method. The resulting electromagnetic matrixelements for transitions from excited states in 69,71,73Cu nuclei are used to assess the collective or single-particlecharacter of these states. The results are compared with predictions of large-scale shell-model calculations, givingfurther insight into the evolution of the proton pf shell as neutrons fill the 1g9/2 orbital.

Nucleon transfer reactions at energies close to the Coulomb barrier always played an important role in nuclear structure and reaction dynamics studies. It has been shown that heavy-ion reactions are an ideal tool for the study of the residual interaction in nuclei, in particular the components responsible for the couplings and correlations. The main subject of the present thesis is the study of the properties of the nuclear force which are not accounted for by the mean field description, especially the role played by neutron-proton correlations. This has been addressed by measurements of multinucleon transfer reactions performed with the new generation magnetic spectrometer PRISMA and its ancillary detectors. The experimental differential and total cross sections and total kinetic energy loss distributions for the final reaction products have been extracted and compared with the predictions of the GRAZING model for heavy-ion transfer reactions, based on semi-classical theory. The main objective was to search for an experimental signature of transfer of correlated neutron-proton pairs in the region near the Z =20 and N =20 shell closures. Through the simultaneous study of the absolute cross sections for all channels populated via transfer of nucleon pairs (±nn), (±pp) and (±np), and their comparison with the theoretical predictions, we explored the possible effect of (np) correlation. The findings have been also corroborated with results obtained at energies below the Coulomb barrier, where the excitation energies of the final reaction products are expected to be small. The comparison of the experimental results with the semi-classical calculations that include only the transfer of independent particles shows that the experimental cross section of (+1p+1n) channel is enhanced, indicating the possibility of a presence of a (np) pair degree of freedom. The analysis of these inclusive data was corroborated by a complementary analysis of γ-particle coincidences, where PRISMA has been used in coupled operation with the CLARA γ array. From the analysis of these coincidences, the population strength of excited states has been extracted for different transfer channels. In particular, for 42K, reached via the (+1p+1n) channel, a strong population of the 7+ state has been evidenced. Since this can happen when a neutron and a proton occupy the same f7/2 orbital, the finding may give a further support to the presence of a neutron-proton correlation. Reakcije prijenosa nukleona na energijama blizu kulonske barijere važne su i u proučvanju strukture jezgara i mehanizma reakcije. Pokazalo se da su teškoionske reakcije odličan način proučavanja rezidualne interakcije u jezgrama, naročito dijelova odgovornih za vezanje i korelacije. Glavna tema ovog doktorskog rada je proučavanje svojstava nuklearne sile koja nisu uključena u opis pomoću srednjeg polja, posebno uloga korelacija između neutrona i protona. To se proučavalo mjerenjem reakcije prijenosa mnogo nukleona s magnetskim spektrometrom velikoga prostornoga kuta PRISMA i njegovim pomoćnim detektorima. Dobiveni su diferencijalni i ukupni udarni presjek, raspodjela gubitka kinetičke energije za sve produkte reakcije, te su uspoređeni s teorijskim predviđanjima modela GRAZING. Glavna ideja je potraga za eksperimentalnim potpisom prijenosa koreliranog para neutron-proton u području blizu Z = 20 i N = 20 zatvorenih ljusaka. Istodobnom usporedbom apsolutnog udarnog presjeka za sve kanale koje su pobuđeni prijenosom para nukleona, (±nn), (±pp) i (±np), te njihovom usporedbom s teorijskim predviđanjima, traženi su mogući efekti (np) korelacija. Rezultati su potvrđeni s rezultatima dobivenim na energijama ispod kulonske barijere, gdje se očekuju male energije pobuđenja produkata reakcije. Usporedba mjerenih rezultata s polu-klasičnim računima koji uključuju samo prijenos neovisnih čestica pokazuje da je (+1p+1n) kanal pojačan, što može ukazivati na moguć doprinos (np) korelacija. Analiza inkluzivnih podataka je nadopunjena dodatnom analizom γ-fragment koincidencija, kada je PRISMA korištena s CLARA γ detektorom. Ove koincidencije omogućuju proučavanje snage pobuđenja različitih stanja. 42K kanal, pobuđen putem prijenosa jednog protona i neutrona, pokazuje jako pobuđenje 7+ stanja. Taj rezultat se može shvatiti kao dodatna potvrda prisutnosti korelacije neutron-proton, jer se 7+ stanje može opisati kao stanje u kojem su neutron i proton u istoj f7/2 orbitali.

The main idea of the two presented experiments is to study the decay of resonances in 24Mg at excitation energies above the 12C+12C decay threshold, in the astrophysical energy region of interest. The measurement of the 12C(16O, gamma)24Mg* reaction was performed at INFN-LNS in Catania. Only the alpha+20Ne decay channel of 24Mg is presented here, because it was a motivation for conducting a new experiment, a study of the4He(20Ne, 4He)20Ne reaction, performed at INFN-LNL in Legnaro. Some preliminary results of this measurement are also presented.

The fusion excitation function of the system 28Si + 28Si at energies near and below the Coulomb barrier is known only down to ~15 mb. This precludes any information on both coupling effects on sub-barrier cross sections and the possible appearance of hindrance. The sub-barrier cross sections for 28Si + 28Si are overestimated by coupled-channels calculations based on a standard Woods-Saxon potential, except for the lowest energies. Calculations using the M3Y+repulsion potential are adjusted to fit the 28Si + 28Si and the existing 30Si + 30Si data. An additional weak imaginary potential is required to fit the low-energy trend of 28Si + 28Si.

Resonant elastic scattering of 13C on a thick 4He target has been measured. Reaction products from 13C(4He, 4He) were detected at several beam energies and gas pressures. Raw yield was effciency corrected using Monte Carlo simulations and an averaged yield spectrum was produced. The observed peaks correspond well to the previously measured elastic scattering data.

Multinucleon transfer reaction 40Ar+208Pb has been investigated with the PRISMACLARA experimental setup in LNL, INFN, Italy. The experimental differential cross sections have been obtained for different transfer channels by measuring more than Δθlab = 20◦ covered by three angular settings of PRISMA. Results have been compared with the semiclassical calculation GRAZING. Since the understanding of the reaction mechanism depends strongly on the determination of absolute cross section, effect of transport of ions through PRISMA has been studied via a Monte Carlo simulation code.

The fusion excitation function of 32S+48Ca has been measured in a wide energy range, from above the Coulomb barrier down to cross sections in the sub-μb region. The excitation function has a smooth behavior below the barrier with a rather flat slope, and no maximum of astrophysical factor S vs. energy has been observed. However, other interesting features of the dynamics of this system can be noted. In particular, the fusion barrier distribution has an unusual shape with two peaks of similar height, lower and higher than the Akyu¨z-Winther barrier. Preliminary coupledchannels calculations and a comparison with nearby systems yield information on the possible influence of nucleon transfer channels with positive Q-value.

The 14N(p, γ)15O reaction is the slowest process of the CN cycle, and thus it is of high astrophysical interest since it regulates the total rate of energy and neutrinos production through the cycle. The 14N+p ground state capture is strongly influenced by a sub-threshold resonance corresponding to the 6.79 MeV state in 15O. The width of this resonance is a major source of uncertainty in the extrapolation of the reaction cross section in the Gamow energy window. Preliminary results of a new Doppler Shift Attenuation measurement of the lifetime of the 6.79 MeV state in 15O are discussed. The level of interest was populated via the 2H(14N, n)15O reaction in inverse kinematics at 32 MeV beam energy. The gamma-rays emitted in the decay of the 6.79 MeV level to the ground state were detected with the AGATA Demonstrator array of high-purity germanium detectors. The sensitivity of the shape of the peak in the gamma-ray energy spectrum to the level lifetime is investigated comparing the experimental peaks with detailed Monte Carlo simulations of the reaction mechanisms and the gamma-ray emission and detection. Nuclear levels in 15N (also populated in the 14N+2H reaction) for which the lifetimes are known in the literature provided a test of the analysis technique.

Želimo li objasniti nukleosintezu elemenata, moramo spojiti dva naizgled suprotna ekstrema svemira: njegove gotovo najmanje objekte (atomske jezgre) s ponajvećima (zvijezdama, galaksijama i svemirom u cjelini). Atomske jezgre su na scenu povijesti stupile vrlo rano. U primordijalnoj nukleosintezi, koja završava 3 minute nakon Big Banga, formirane su najlakše jezgre: 2H, 3He, 4He, 6Li i 7Li. Sve teže jezgre generirane su u nuklearnim reakcijama koje se odvijaju u svim fazama života zvijezda - od mirnog gorenja vodika u pp i CNO ciklusima, preko eksplozivnog gorenja helija, ugljika i težih elemenata u kojima nastaju elementi do željeza, do s i r procesa koje čine reakcije izazvane neutronima. U eksplozijama supernova prerađeni zvjezdani materijal i najteži stvoreni elementi raspršuju se u svemir, te tako postaju dijelom novih zvijezda i planeta. Danas, 13,7 milijardi godina nakon nastanka prvih jezgri, u svijetu kakvog poznajemo imamo 92 prirodna elementa i preko 3100 prirodnih i umjetnih izotopa! Važan zadatak nuklearne fizike je rasvijetliti vrlo složene puteve odvijanja reakcija u zvijezdama i svojima otkrićima objasniti zastupljenost elemenata koju danas uočavamo. Naročito su bitni eksperimenti koji uključuju jezgre 12C i 16O, s obzirom da je omjer tih elemenata odigrao ključnu ulogu u razvoju života u svemiru. Predstavljena su tri eksperimenta koja se tiču reakcija bitnih za nukleosintezu na kojima su sudjelovali autori ovog postera: posredno mjerenje reakcije 12B→8Li + 4He, koja je vrlo važna za modeliranje nukleosinteze u slučaju nehomogenog ranog svemira; izučavanje najsporijeg procesa u CNO ciklusu 14N(p, γ)15O; istraživanje strukture jezgre 17O rezonantnim raspršenjem 13C na 4He.

Reakcija prijenosa mnogo nukleona 40Ar+208Pb mjerena je na energiji snopa 255 MeVa s PRISMA-CLARA detektorskim sustavom u Laboratori Nazionali di Legnaro, Italija. Magnetski spektrometar PRISMA zbog svog velikog prostornog kuta detektira čestice slične projektilu u širokom rasponu mase i kinetičke energije. Koincidentne gamma zrake zabilježene su HPGe gamma detektorima CLARA. Kutna raspodjela je mjerena s tri različite postavke PRISMA spektrometra, s preklapajućim kutnim rasponom. Njihova normalizacija je napravljena sa silicijskim detektorom na prednjim kutevima i dobiveno je odlično slaganje. Ipak, mala odstupanja su i dalje prisutna na rubovima raspodjele zbog čega je nužno poznavati funkciju odgovora spektrometra. Nju dobivamo pomoću Monte Carlo simulacije, te je možemo primijeniti, osim za korekciju kutne raspodjele, i za dobivanje potpunog udarnog presjeka.

U brosuri je objasnjeno postojanje razlicitih atomskih jezgara, njihov nastanak i egzoticni fenomeni koji se javljaju u odredenim izotopima. te koja je implikacija svojstava takvih izotopa na svijet koji nas okruzuje.

Measurements of 9Be+α resonant scattering have been performed using the thick-target approach with a 4He gas volume and a large area silicon strip detector. 9Be beam energies in the range 12 to 21.4 MeV were used to measure the 13C excitation energy spectrum between 13.2 and 16.2 MeV. An R-matrix analysis has been performed to characterize the spins and widths of 13C resonances, some of which have been proposed to be associated with a 3α+n molecular band.

Moderni detektori u nuklearnoj fizici pokrivaju sve veći prostorni kut, te sa sve većom efikasnošću bilježe jednostruke i višestruke događaje nakon nuklearnih reakcija, što omogućuje proučavanje procesa vrlo malene vjerojatnosti odvijanja. Među takve spada i višestruko nuklearno raspršenje, tj. proces u kojem se jezgra iz snopa više puta rasprši na raznim jezgrama mete. Još je manje vjerojatan proces u kojem bi se u jednom koraku umjesto raspršenja odigrala reakcija prijenosa nukleona. U okviru diplomskog rada eksperimentalno je proučena mogućnost detekcije takvih procesa na konkretnom primjeru, reakciji 12C+d->13C*+p praćenoj raspršenjem 13C*+12C. Mjerenje je izvršeno na ubrzivaču Tandem Van de Graaff Instituta "Ruđer Bošković" u Zagrebu uz upotrebu poluvodičkih detektora nabijenih čestica. Analiza podataka je napravljena kako bi se pokazao potencijal ovakvih mjerenja za primjene u spektroskopiji egzotičnih nuklearnih stanja.