Search

Multi-Nucleon Transfer (MNT) reactions have been used for decades as a reaction mechanism, in order to populate excited states in nuclei far from stability and to perform nuclear structure studies. Nevertheless, the development of set-ups involving high acceptance tracking magnetic spectrometers (mainly existing in Europe), coupled with the Advanced GAmma Tracking Array (AGATA) opens new possibilities, especially if they are used in conjunction with high-intensity stable beams or ISOL RIBs. In this article, we will discuss the capabilities of such set-ups aiming at different goals, including complete information in high-resolution spectroscopy as well as lifetime measurements.

The systematics of the lowest 2+ energies of even-even nuclei, and the B(E2) rates connecting those levels to the ground states, give essential information about the degree of collectivity in various regions of the nuclide chart. The B(E2) rates provide crucial tests of theoretical predictions, such as the quenching of shell structure in neutron-rich nuclei. Measurements of such rates are in progress using multi-nucleon transfer reactions and radioactive ion beams. We have measured the fusion excitation functions for the three systems 48Ca + 116Cd, 118Sn, 120Te, in the relevant energy range from above to below the Coulomb barrier. The magic projectile 48Ca has been chosen in view of its spherical and rigid structure, while the three targets have proton numbers Z=48, 50, 52. We observe that the cross sections are smallest for the target 118Sn, thus indicating the effect on sub-barrier fusion of crossing the major shell closure at Z = 50. This suggests the possibility of using near-barrier fusion reactions of radioactive ion beams with suitable stable targets, as a complementary technique to evidence the low-lying nuclear structure of exotic nuclei, besides well established methods.

Background: The phenomenon of fusion hindrance may have important consequences on the nuclear processes occurring in astrophysical scenarios, if it is a general behavior of heavy-ion fusion at extreme subbarrier energies, including reactions involving lighter systems, e.g., reactions in the carbon and oxygen burning stages of heavy stars. The hindrance is generally identified by the observation of a maximum of the $S$ factor vs energy. Whether there is an $S$-factor maximum at very low energies for systems with a positive fusion $Q$ value is an experimentally challenging question.Purpose: Our aim has been to search for evidence of fusion hindrance in $^{12}\mathrm{C}+^{24}\mathrm{Mg}$ which is a medium-light system with positive $Q$ value for fusion, besides the heavier cases where hindrance is recognized to be a general phenomenon. $^{12}\mathrm{C}+^{24}\mathrm{Mg}$ is very close to the $^{16}\mathrm{O}+^{16}\mathrm{O}$ and $^{12}\mathrm{C}+^{12}\mathrm{C}$ systems that are important for the late evolution of heavy stars.Methods: The experiment has been performed in inverse kinematics using the $^{24}\mathrm{Mg}$ beam from the XTU Tandem accelerator of LNL in the energy range 26--52 MeV with an intensity of 4--8 pnA. The targets were $^{12}\mathrm{C}$ evaporations $50\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{g}/{\mathrm{cm}}^{2}$ thick, isotopically enriched to $99.9%$. The fusion-evaporation residues were detected at small angles by a $E\ensuremath{-}\mathrm{\ensuremath{\Delta}}E$-ToF detector telescope following an electrostatic beam deflector.Results: Previous measurements of fusion cross section for $^{12}\mathrm{C}+^{24}\mathrm{Mg}$ were limited to above-barrier energies. In the present experiment the excitation function has been extended down to $\ensuremath{\simeq}15\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{b}$ and it appears that the $S$ factor develops a clear maximum vs energy, indicating the presence of hindrance. This is the first convincing evidence of an $S$ factor maximum in a medium-light system with a positive fusion $Q$ value. These results have been fitted following a recently suggested method and a detailed analysis within the coupled-channels model that has been performed using a Woods-Saxon potential and including the ground state rotational band of $^{24}\mathrm{Mg}$. The coupled-channels calculations give a good account of the data near and above the barrier but overpredict the cross sections at very low energies.Conclusions: The hindrance phenomenon is clearly observed in $^{12}\mathrm{C}+^{24}\mathrm{Mg}$, and its energy threshold is in reasonable agreement with the systematics observed for several medium-light systems. The fusion cross sections at the hindrance threshold show that the highest value (${\ensuremath{\sigma}}_{s}=1.6\phantom{\rule{0.28em}{0ex}}\mathrm{mb}$) is indeed found for this system. Therefore it may even be possible to extend the measurements further down in energy to better establish the position of the $S$-factor maximum.

8 pags., 9 figs., We measured absolute cross sections for neutron transfer channels populated in the Rb-94 + Pb-208 binary reaction. Cross sections have been extracted identifying directly the lead isotopes with the high efficiency MINIBALL gamma-ray array coupled to a particle detector combined with a radioactive Rb-94 beam delivered at E-lab = 6.2 MeV/nucleon by the HIE-ISOLDE facility. We observed sizable cross sections in the neutron-rich mass region, where the heavy partner acquires neutrons. A fair agreement between the measured cross sections with those from GRAZING calculations gives confidence in the cross-section predictions of more neutron-rich nuclei produced via a larger number of transferred nucleons., This work was partly supported by the HORIZON 2020 ENSAR2 Grant Agreement no. 654002, and Marie Skłodowska-Curie COFUND (EU-CERN) grant agreement no. 665779, and by STFC (U.K.). This work has been supported in part by the Croatian Science Foundation under Project no. 7194 and in part under Project no. IP-2018-01- 1257, and the German BMBF under contract 05P18PKCIA + Verbundprojekt 05P2018

Lifetimes of excited states of the phosphorus isotopes 1533,34,35,36P 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 S36 ions of energy 225 MeV incident on a thin Pb208 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 P33, 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 P34 at 429 keV was determined and compared with earlier measurements. For P35, 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+, 7/21−, and 7/22−, respectively. There have been no previous published lifetimes for states in this nucleus. A lifetime was measured for the stretched π(1f7/2)⊗ν(1f7/2)Jπ=(7+) state of P36 at 5212 keV and a lifetime limit was established for the stretched π(1d3/2)⊗ν(1f7/2)Jπ=(5−) state at 2030 keV. There are no previously published lifetimes for states of P36. 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 3/21+→1/2+ (ground state) and 5/21+→3/21+ transitions in P33 underestimate the experimental values by a factor between 5 and 10. In P35 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.

Background: $^{58}\mathrm{Ni}+^{64}\mathrm{Ni}$ is the first case where the influence of positive $Q$-value transfer channels on subbarrier fusion was evinced, in a very well known experiment by Beckerman et al. [Phys. Rev. Lett. 45, 1472 (1980)], by comparing with the two systems $^{58}\mathrm{Ni}+^{58}\mathrm{Ni}$ and $^{64}\mathrm{Ni}+^{64}\mathrm{Ni}$. Subsequent measurements on $^{64}\mathrm{Ni}+^{64}\mathrm{Ni}$ showed that fusion hindrance is clearly present in this case. On the other hand, no indication of hindrance can be observed for $^{58}\mathrm{Ni}+^{64}\mathrm{Ni}$ down to the measured level of 0.1 mb.Purpose: Measuring deep subbarrier fusion cross sections for $^{58}\mathrm{Ni}+^{64}\mathrm{Ni}$, where the influence of positive $Q$-value transfer channels on near-barrier fusion was evidenced previously, in order to investigate whether hindrance shows up.Methods: 167--200 MeV $^{58}\mathrm{Ni}$ beams from the XTU Tandem Accelerator of INFN-Laboratori Nazionali di Legnaro were used, bombarding thin metallic $^{64}\mathrm{Ni}\phantom{\rule{4pt}{0ex}}(50\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{g}/{\mathrm{cm}}^{2})$ enriched to $99.6%$ in mass 64. An electrostatic beam deflector allowed fusion evaporation residues to be detected at very forward angles in a detector telescope.Results: The excitation function has been extended by two orders of magnitude downward. The cross sections for $^{58}\mathrm{Ni}+^{64}\mathrm{Ni}$ continue decreasing very smoothly below the barrier, down to $\ensuremath{\simeq}1\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{b}$. The logarithmic slope of the excitation function increases slowly, showing a tendency to saturate at the lowest energies. No maximum of the astrophysical $S$ factor is observed. Coupled-channel (CC) calculations using a Woods-Saxon potential and including inelastic excitations only underestimate the subbarrier cross sections by a large amount. Good agreement is found by adding two-nucleon transfer couplings to a schematical level. This behavior is quite different from what already observed for $^{64}\mathrm{Ni}+^{64}\mathrm{Ni}$ (no positive $Q$-value transfer channels available), where a clear low-energy maximum of the $S$ factor appears, and whose excitation function is overestimated by a standard Woods-Saxon CC calculation.Conclusions: No hindrance effect is observed in $^{58}\mathrm{Ni}+^{64}\mathrm{Ni}$ in the measured energy range. This trend at deep subbarrier energies reinforces the recent suggestion that the availability of several states following transfer with $Qg0$ effectively counterbalances the Pauli repulsion that, in general, is predicted to reduce tunneling probability inside the Coulomb barrier.

The transitional nuclei $^{134}$Ba and $^{133}$Ba are investigated after multinucleon transfer employing the high-resolution Advanced GAmma Tracking Array coupled to the magnetic spectrometer PRISMA at the Laboratori Nazionali di Legnaro, Italy, and after fusion-evaporation reaction at the FN tandem accelerator of the University of Cologne, Germany. The Jπ=19/2+ state at 1942 keV in $^{133}$Ba is identified as an isomer with a half-life of 66.6(20)ns corresponding to a B(E1) value of 7.7(4)×10−6e2fm2 for the Jπ=19/2+ to Jπ=19/2− transition. The level scheme of $^{134}$Ba above the Jπ=10+ isomer is extended to approximately 6 MeV. A pronounced backbending is observed at ℏω=0.38 MeV along the positive-parity yrast band. The results are compared to the high-spin systematics of the Z=56 isotopes. Large-scale shell-model calculations employing the GCN50:82, SN100PN, SNV, PQM130, Realistic SM, and EPQQM interactions reproduce the experimental findings and elucidate the structure of the high-spin states. The shell-model calculations employing the GCN50:82 and PQM130 interactions reproduce alignment properties and provide detailed insight into the microscopic origin of this phenomenon in transitional $^{134}$Ba.

International audience; Sub-barrier fusion of the two near-by systems$^{36}$S +$^{50}$Ti,$^{51}$V has been measured at the Laboratori Nazionali di Legnaro (INFN). Motivation for the experiment came from the possible effect of the non-zero spin of the ground state of the$^{51}$V nucleus on the sub-barrier excitation function, and in particular on the shape of the barrier distribution. No previous data were available for these two systems near the barrier. Our results show that the two measured excitation functions are very similar down to the level of 20-30μb. The same is true for the two barrier distributions. Coupled-channel calculations have been performed including the low energy excitations of both projectile and the two targets. We have indication that the low-lying levels in$^{51}$V can be interpreted in the weak-coupling scheme, that is,$^{51}$V (I) =$^{50}$Ti(2$^{+}$) ⊗ p(1f$_{7/2}$) and that the extra proton in the $ 1f_{7/2}$ shell does not have a significant influence on sub-barrier fusion.

The high-spin structures of 136Ba and 137Ba are investigated after multinucleon-transfer (MNT) and fusion-evaporation reactions. 136Ba is populated in a 136Xe+238U 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 9Be + 130Te fusion-evaporation reactions using the High-efficiency Observatory for -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 11B+130Te fusion-evaporation reaction utilizing the HORUS -ray array. The level scheme above the J� = 10+ isomer in 136Ba is revised and extended up to an excitation energy of approx. 5.5 MeV. From the results of angular-correlation measurements, the Ex = 3707- and Ex = 4920-keV states are identified as the bandheads of positive- and negative-parity cascades. While the high-spin regimes of both 132Te and 134Xe are characterized by high-energy 12+ ! 10+ transitions, the 136Ba E2 ground-state band is interrupted by negativeparity states only a few hundred keV above the J� = 10+ isomer. Furthermore, spins are established for several hitherto unassigned high-spin states in 137Ba. The new results close a gap along the highspin 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.

The phenomenon of fusion hindrance may have important consequences on the nuclear processes occurring in astrophysical scenarios, if it is a general behaviour of heavy-ion fusion at extreme sub-barrier energies, including reactions involving lighter systems, e.g. reactions in the carbon and oxygen burning stages of heavy stars. The hindrance is generally identified by the observation of a maximum of the S-factor vs. energy. Whether there is an S-factor maximum at very low energies for systems with a positive fusion Q-value is an experimentally challenging question. Our aim has been to search evidence for fusion hindrance in 12C + 24Mg which is a medium-light systems with positive Q-value for fusion, besides the heavier cases where hindrance is recognised to be a general phenomenon. The experiment has been performed at the XTU Tandem accelerator of LNL by directly detecting the fusion evaporation residues at very forward angles. The excitation function has been extended down to ≃10μb, i.e. 4 orders of magnitude lower than previous measurements and we observe that the S-factor develops a clear maximum vs. energy. Coupled-Channels calculations using a Woods-Saxon potential give a good account of the data near and above the barrier but over predict the cross sections at very low energies. Therefore the hindrance phenomenon is clearly recognised in 12 C + 24 Mg with an energy threshold that nicely fits the systematics in several medium-light systems. The fusion cross sections at the hindrance threshold show that the highest value (as=1.6mb) is indeed found for this system. It may be possible to extend the measurements further down in energy.

Detailed information on isomeric states in A ≈ 135 nuclei is exploited to benchmark shell-model calculations in the region northwest of doubly-magic nucleus 132Sn. The N = 79 isotones 133Xe and 135Ba are studied after multinucleon transfer (MNT) in the 136Xe + 208Pb 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 a pulsed-beam experiment at the FN tandem accelerator of the University of Cologne, Germany utilizing a 9Be+130Te fusion-evaporation reaction at a beam energy of 40 MeV. Isomeric states are identified via delayed γ-ray spectroscopy. Hitherto tentative excitation energy, spin, and parity assignments of the 2107-keV Jπ = 23/2+ isomer in 133Xe are confirmed and a half-life of T1/2 = 8.64(13) ms is measured. The 2388-keV state in 135Ba is identified as a Jπ = 23/2+ isomer with a half-life of 1.06(4) ms. The new results show a smooth onset of isomeric Jπ = 23/2+ states along the N = 79 isotones and close a gap in the high-spin systematics towards the recently investigated Jπ = 23/2+ isomer in 139Nd. The resulting systematics of M2 reduced transition probabilities is discussed within the framework 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.

The transitional nucleus 131Xe is investigated after multinucleon transfer (MNT) in the 136Xe+208Pb and 136Xe+238U reactions employing the high-resolution Advanced GAmma 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 HORUS γ-ray array coupled to a double-sided silicon strip detector (DSSSD) at the University of Cologne, Germany. The level scheme of 131Xe is extended to 5 MeV. A pronounced backbending is observed at ~ω ≈ 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 (LSSM) 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 $^{12}\mathrm{C}+\text{Pb}$ 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.

We studied multinucleon transfer reactions in the 197Au+130Te 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.

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.

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.

Background: While the $N=50$ shell-gap evolution towards $^{78}\mathrm{Ni}$ is presently in the focus of nuclear structure research, experimental information on the neutron effective single-particle energy sequence above the $^{78}\mathrm{Ni}$ 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 $\ensuremath{\nu}1{g}_{7/2}$ 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 $^{78}\mathrm{Ni}$ region. To achieve this goal, a method based on lifetime measurements is used for the first time. The obtained lifetimes of the $7/{2}_{1}^{+}$ states in $^{87}\mathrm{Kr}$ and $^{85}\mathrm{Se}$ are used to investigate the $\ensuremath{\nu}1{g}_{7/2}$ evolution.Method: Yrast and near-yrast states in the light $N=51$ isotones $^{85}\mathrm{Se}$ and $^{87}\mathrm{Kr}$ were populated via multinucleon transfer reactions, using a $^{82}\mathrm{Se}$ beam and a $^{238}\mathrm{U}$ target at the LNL tandem-ALPI facility. The prompt $\ensuremath{\gamma}$ 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 ${\ensuremath{\tau}}_{(7/{2}_{1}^{+})}=0.{4}_{\ensuremath{-}0.4}^{+1.6}$ ps for $^{87}\mathrm{Kr}$. In the case of $^{85}\mathrm{Se}$ an upper limit of 3(2) ps is obtained for the ${\ensuremath{\tau}}_{7/{2}_{1}^{+}}$ value.Conclusion: For $^{87}\mathrm{Kr}$, the measured $(7/{2}_{1}^{+})$ lifetime is consistent with a core-coupled ${2}^{+}\ensuremath{\bigotimes}\ensuremath{\nu}2{d}_{5/2}$ configuration for this state. This result is consistent with that obtained by direct reaction, which validates our method. For $^{85}\mathrm{Se}$, the measured $7/{2}_{1}^{+}$ lifetime limit indicates a very small contribution of the $\ensuremath{\nu}1{g}_{7/2}$ configuration to the wave function of this state.

We report on the direct experimental observation of the 7pP2

Author(s): Vogt, A; Siciliano, M; Birkenbach, B; Reiter, P; Hadynska-Klȩk, K; Wheldon, C; Valiente-Dobon, JJ; Teruya, E; Yoshinaga, N; Arnswald, K; Bazzacco, D; Blazhev, A; Bracco, A; Bruyneel, B; Chakrawarthy, RS; Chapman, R; Cline, D; Corradi, L; Crespi, FCL; Cromaz, M; De Angelis, G; Eberth, J; Fallon, P; Farnea, E; Fioretto, E; Fransen, C; Freeman, SJ; Fu, B; Gadea, A; Gelletly, W; Giaz, A; Gorgen, A; Gottardo, A; Hayes, AB; Hess, H; Hetzenegger, R; Hirsch, R; Hua, H; John, PR; Jolie, J; Jungclaus, A; Karayonchev, V; Kaya, L; Korten, W; Lee, IY; Leoni, S; Liang, X; Lunardi, S; MacChiavelli, AO; Menegazzo, R; Mengoni, D; Michelagnoli, C; Mijatovic, T; Montagnoli, G; Montanari, D; Muller-Gatermann, C; Napoli, D; Pearson, CJ; Podolyak, Z; Pollarolo, G; Pullia, A; Queiser, M; Recchia, F; Regan, PH; Regis, JM; Saed-Samii, N; Sahin, E; Scarlassara, F; Seidlitz, M; Siebeck, B; Sletten, G; Smith, JF; Soderstrom, PA; Stefanini, AM; Stezowski, O; Szilner, S; Szpak, B; Teng, R; Ur, C; Warner, DD; Wolf, K; Wu, CY; Zell, KO | Abstract: The transitional nuclei Xe132 and Xe133 are investigated after multinucleon-transfer (MNT) and fusion-evaporation reactions. Both nuclei are populated (i) in Xe136+Pb208 MNT reactions employing the high-resolution Advanced GAmma Tracking Array (AGATA) coupled to the magnetic spectrometer PRISMA, (ii) in the Xe136+Pt198 MNT reaction employing the GAMMASPHERE spectrometer in combination with the gas-detector array CHICO, and (iii) as an evaporation residue after a Te130(α,xn)Xe134-xn fusion-evaporation reaction employing the HORUS γ-ray array at the University of Cologne. The high-spin level schemes are considerably extended above the Jπ=(7-) and (10+) isomers in Xe132 and above the 11/2- isomer in Xe133. The results are compared to the high-spin systematics of the Z=54 as well as the N=78 and N=79 chains. Furthermore, evidence is found for a long-lived (T1/2â‰1μs) isomer in Xe133 which closes a gap along the N=79 isotones. Shell-model calculations employing the SN100PN and PQM130 effective interactions reproduce the experimental findings and provide guidance to the interpretation of the observed high-spin features.

Angular distributions of $ \gamma$ -rays for selected transitions in 40, 41, 42Ar isotopes have been studied with the PRISMA magnetic spectrometer coupled to the CLARA $ \gamma$ 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^-) \rightarrow 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.

The neutron-rich nucleus \nucleus{200}{Pt} is investigated via in-beam \gamma-ray spectroscopy in order to study the shape evolution in the neutron-rich platinum isotopes towards the N = 126 shell closure. The two-neutron transfer reaction \nucleus{198}{Pt}(\nucleus{82}{Se}, \nucleus{80}{Se})\nucleus{200}{Pt} is used to populate excited states of \nucleus{200}{Pt}. The Advanced Gamma Ray Tracking Array (AGATA) demonstrator coupled with the PRISMA spectrometer detects \gamma rays coincident with the \nucleus{80}{Se} recoils, the binary partner of \nucleus{200}{Pt}. The binary partner method is applied to extract the \gamma-ray transitions and build the level scheme of \nucleus{200}{Pt}. The level at 1884\,keV reported by Yates et. al [Phys. Rev. C 37, 1889] was confirmed to be at 1882.1\,keV and assigned as the (6^+_1) state. An additional \gamma ray was found and it presumably de-excites the (8^+_1) state. The results are compared with state-of-the-art beyond mean-field calculations, performed for the even-even \nucleus{190-204}{Pt} isotopes, revealing that \nucleus{200}{Pt} marks the transition from the \gamma-unstable behaviour of lighter Pt nuclei towards a more spherical one when approaching the N=126 shell closure.

This contribution reports on the results of measurements of near- and sub-barrier fusion cross sections in the system $^{30}$Si+$^{30}$Si performed at the Laboratori Nazionali di Legnaro of INFN. The $^{30}$Si beam of the XTU Tandem accelerator in the energy range of 47 - 90 MeV, was delivered on a metallic $^{30}$Si target (50 $\mu$g/cm$^{2}$) enriched to 99.64 $\%$ in mass 30. A beam electrostatic deflector was used for the detection of evaporation residues. The excitation function obtained for $^{30}$Si+$^{30}$Si has been compared with the previous data on $^{28}$Si+$^{28}$Si and Coupled Channels (CC) calculations using the M3Y+repulsion potential, taking into account the low lying 2$^+$ and 3$^-$ excitations. Reproducing the low-energy $^{28}$Si+$^{28}$Si excitation function was only possible by using a weak imaginary potential, probably simulating the oblate deformation of this nucleus. On the contrary, the data on $^{30}$Si+$^{30}$Si are nicely reproduced by the CC calculations without any imaginary potential ($^{30}$Si has a spherical shape). The astrophysical S-factor does not show a maximum, so that there is no evidence for hindrance in the measured energy range. The logarithmic derivative of the two excitation functions highlights the difference between the two systems. Even above the barrier the two systems behave differently. This is best seen by comparing the two barrier distributions where the high energy peak observed for $^{28}$Si+$^{28}$Si is not found for $^{30}$Si+$^{30}$Si. This is presumably due to the stronger couplings present in $^{28}$Si and further theoretical analyses are in progress.

The high-spin structures of the N = 81 isotones 135Xe and 137Ba are investigated after multinucleontransfer (MNT) and fusion-evaporation reactions. Both nuclei are populated in (i) 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 -ray array GAMMASPHERE in combination with the gas detector array Chico, and (iv) via a 11B+130Te fusion-evaporation reaction. 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, completing the systematics for the N = 81 isotones. Its half-life is measured to be 8.6(10) ns, corresponding to a transition probability of B(E2; 19=2 ! 15=2 ) = 0:539(69) W.u. Latest shell model calculations considering 132Sn as a closed core reproduce the experimental findings and provide guidance to the interpretation of the new levels. The experimentally deduced reduced quadrupole transition probabilities of the isomeric states are compared to shell-model predictions.

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. Comparisons 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 pickup, whose behavior in connection with the production of neutron-rich heavy partner has been outlined.

We present selected results recently obtained in the study of heavy ion transfer reactions at energies close to the Coulomb barrier by employing the large solid angle magnetic spectrometer PRISMA. We discuss the production of neutron-rich heavy nuclei via multinucleon transfer processes and the related effects of secondary processes, in particular nucleon evaporation, studied in a high resolution kinematic coincidence experiment. We also present the recent results in the studies of neutron-neutron correlations for closed shell and superfluid systems.

Background: $^{58}\mathrm{Ni}+^{64}\mathrm{Ni}$ is the first case where the influence of positive $Q$-value transfer channels on subbarrier fusion was evinced, in a very well known experiment by Beckerman et al. [Phys. Rev. Lett. 45, 1472 (1980)], by comparing with the two systems $^{58}\mathrm{Ni}+^{58}\mathrm{Ni}$ and $^{64}\mathrm{Ni}+^{64}\mathrm{Ni}$. Subsequent measurements on $^{64}\mathrm{Ni}+^{64}\mathrm{Ni}$ showed that fusion hindrance is clearly present in this case. On the other hand, no indication of hindrance can be observed for $^{58}\mathrm{Ni}+^{64}\mathrm{Ni}$ down to the measured level of 0.1 mb.Purpose: Measuring deep subbarrier fusion cross sections for $^{58}\mathrm{Ni}+^{64}\mathrm{Ni}$, where the influence of positive $Q$-value transfer channels on near-barrier fusion was evidenced previously, in order to investigate whether hindrance shows up.Methods: 167--200 MeV $^{58}\mathrm{Ni}$ beams from the XTU Tandem Accelerator of INFN-Laboratori Nazionali di Legnaro were used, bombarding thin metallic $^{64}\mathrm{Ni}\phantom{\rule{4pt}{0ex}}(50\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{g}/{\mathrm{cm}}^{2})$ enriched to $99.6%$ in mass 64. An electrostatic beam deflector allowed fusion evaporation residues to be detected at very forward angles in a detector telescope.Results: The excitation function has been extended by two orders of magnitude downward. The cross sections for $^{58}\mathrm{Ni}+^{64}\mathrm{Ni}$ continue decreasing very smoothly below the barrier, down to $\ensuremath{\simeq}1\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{b}$. The logarithmic slope of the excitation function increases slowly, showing a tendency to saturate at the lowest energies. No maximum of the astrophysical $S$ factor is observed. Coupled-channel (CC) calculations using a Woods-Saxon potential and including inelastic excitations only underestimate the subbarrier cross sections by a large amount. Good agreement is found by adding two-nucleon transfer couplings to a schematical level. This behavior is quite different from what already observed for $^{64}\mathrm{Ni}+^{64}\mathrm{Ni}$ (no positive $Q$-value transfer channels available), where a clear low-energy maximum of the $S$ factor appears, and whose excitation function is overestimated by a standard Woods-Saxon CC calculation.Conclusions: No hindrance effect is observed in $^{58}\mathrm{Ni}+^{64}\mathrm{Ni}$ in the measured energy range. This trend at deep subbarrier energies reinforces the recent suggestion that the availability of several states following transfer with $Qg0$ effectively counterbalances the Pauli repulsion that, in general, is predicted to reduce tunneling probability inside the Coulomb barrier.

We investigate a region of the Galactic plane, between 120, 21 pages, 13 figures. Accepted for publication in MNRAS

The neutron-rich $^{39}\mathrm{S}$ nucleus has been studied using binary grazing reactions produced by the interaction of a 215-MeV beam of $^{36}\mathrm{S}$ ions with a thin $^{208}\mathrm{Pb}$ target. The magnetic spectrometer, PRISMA, and the $\ensuremath{\gamma}$-ray array, CLARA, were used in the measurements. Gamma-ray transitions of the following energies were observed: 339, 398, 466, 705, 1517, 1656, and 1724 keV. Five of the observed transitions have been tentatively assigned to the decay of excited states with spins up to ($11/{2}^{\ensuremath{-}}$). The results of a state-of-the-art shell-model calculation of the level scheme of $^{39}\mathrm{S}$ using the SDPF-U effective interaction are also presented. The systematic behavior of the excitation energy of the first $11/{2}^{\ensuremath{-}}$ states in the odd-$A$ isotopes of sulfur and argon is discussed in relation to the excitation energy of the first excited ${2}^{+}$ states of the adjacent even-$A$ isotopes. The states of $^{39}\mathrm{S}$ that have the components in their wave functions corresponding to three neutrons in the $1{f}_{7/2}$ orbital outside the $N=20$ core have also been discussed within the context of the 0 $\ensuremath{\hbar}\ensuremath{\omega}$ shell-model calculations presented here.

We performed a γ -particle coincidence experiment for the 60Ni+116Sn system to investigate whether the population of the two-neutron pickup channel leading to 62Ni is mainly concentrated in the ground-state transition, as has been found in a previous work [D. Montanari et al., Phys. Rev. Lett. 113, 052501 (2014)]. The experiment has been performed by employing the PRISMA magnetic spectrometer coupled to theAdvanced 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-state to ground-state transition.

The level structures of the N = 50 83As, 82Ge, and 81Ga isotones have been investigated by means of multi-nucleon transfer reactions. A first experiment was performed with the CLARA–PRISMA setup to identify these nuclei. A second experiment was carried out with the GASP array in order to deduce the γ-ray coincidence information. The results obtained on the high-spin states of such nuclei are used to test the stability of the N = 50 shell closure in the region of 78Ni ( Z = 28 ). The comparison of the experimental level schemes with the shell-model calculations yields an N = 50 energy gap value of 4.7(3) MeV at Z = 28 . This value, in a good agreement with the prediction of the finite-range liquid-drop model as well as with the recent large-scale shell model calculations, does not support a weakening of the N = 50 shell gap down to Z = 28 .

Reduced quadrupole transition probabilities for low-lying transitions in neutron-rich Se-84,Se-86 are investigated with a recoil distance Doppler shift (RDDS) experiment. The experiment was perform ...

Background: No data on the fusion excitation function of $^{48}\mathrm{Ti}+^{58}\mathrm{Fe}$ in the energy region near the Coulomb barrier existed prior to the present work, while fusion of $^{58}\mathrm{Ni}+^{54}\mathrm{Fe}$ was investigated in detail some years ago, down to very low energies, and clear evidence of fusion hindrance was noticed at relatively high cross sections. $^{48}\mathrm{Ti}$ and $^{58}\mathrm{Fe}$ are soft and have a low-lying quadrupole excitation lying at $\ensuremath{\approx}800--900$ keV only. Instead, $^{58}\mathrm{Ni}$ and $^{54}\mathrm{Fe}$ have a closed shell (protons and neutrons, respectively) and are rather rigid.Purpose: We aim to investigate (1) the possible influence of the different structures of the involved nuclei on the fusion excitation functions far below the barrier and, in particular, (2) whether hindrance is observed in $^{48}\mathrm{Ti}+^{58}\mathrm{Fe}$, and to compare the results with current coupled-channels models.Methods: $^{48}\mathrm{Ti}$ beams from the XTU Tandem accelerator of INFN-Laboratori Nazionali di Legnaro were used. The experimental setup was based on an electrostatic beam separator, and fusion-evaporation residues (ERs) were detected at very forward angles. Angular distributions of ERs were measured.Results: Fusion cross sections of $^{48}\mathrm{Ti}+^{58}\mathrm{Fe}$ have been obtained in a range of nearly six orders of magnitude around the Coulomb barrier, down to $\ensuremath{\sigma}\ensuremath{\simeq}2 \ensuremath{\mu}\mathrm{b}$. The sub-barrier cross sections of $^{48}\mathrm{Ti}+^{58}\mathrm{Fe}$ are much larger than those of $^{58}\mathrm{Ni}+^{54}\mathrm{Fe}$. Significant differences are also observed in the logarithmic derivatives and astrophysical $S$ factors. No evidence of hindrance is observed, because coupled-channels calculations using a standard Woods-Saxon potential are able to reproduce the data in the whole measured energy range. Analogous calculations for $^{58}\mathrm{Ni}+^{54}\mathrm{Fe}$ predict clearly too large cross sections at low energies. The two fusion barrier distributions are wide and display a complex structure that is only qualitatively fit by calculations.Conclusions: It is pointed out that all these different trends originate from the dissimilar low-energy nuclear structures of the involved nuclei. In particular, the strong quadrupole excitations in $^{48}\mathrm{Ti}$ and $^{58}\mathrm{Fe}$ produce the relative cross section enhancement and make the barrier distribution $\ensuremath{\approx}2$ MeV wider, thus probably pushing the threshold for hindrance below the measured limit.

With the large solid angle magnetic spectrometer (PRISMA) coupled to the γ-array (CLARA), extensive investigations of nuclear structure and reaction dynamics have been carried out. In the present paper aspects of these studies will be presented, focussing more closely on the reaction mechanism, in particular on the properties of quasielastic and deep inelastic processes and on measurements at energies far below the Coulomb barrier.

With the large solid angle magnetic spectrometer PRISMA coupled to the γ array CLARA extensive investigations have been carried out for nuclear structure and reaction dynamics. In the present paper aspects of these studies will be presented, focusing more closely on the reaction mechanism, in particular on the properties of quasi-elastic and deep-inelastic processes and on measurements at energies far below the Coulomb barrier.

Francium is one of the best candidates for measurements of atomic parity violation and in the search for permanent electric dipole moments. These fundamental measurements rely on precision studies in atomic spectroscopy and on the development of magneto-optical traps. A radioactive francium production and trapping facility was built and commissioned at INFN's national laboratories in Legnaro, Italy. Here we describe the beamline that is used to transport Fr + ions at a kinetic energy of 3 keV from the production target to the magneto-optical trap. The design principles, construction, diagnostics, and performance are discussed.

Recent advances have been achieved in the field of multinucleon transfer reactions among heavy ions, both experimentally and theoretically. Detailed nuclear mass, charge and Q-value distributions allow to identify the relevant degrees of freedom acting in the transfer process. The advent of the large solid angle magnetic spectrometer PRISMA coupled to the large γ -array CLARA was a major experimental breakthrough, as reaction mechanism and nuclear structure studies of neutron rich nuclei can be performed via γ -particle coincidences. Examples of recent studies are presented.

An overview of results in fusion studies with stable beams spanning different mass regions and energy ranges is presented. The advantages offered by studying channel coupling effects, involving low-lying excited states of the colliding nuclei, as well as the difficulties in understanding the influence of transfer couplings on fusion, are firstly remarked. The competition of fusion with quasi-fission in heavy systems and the unexpected steep falloff of fusion cross sections at far sub-barrier energies are finally discussed.

Background: Nuclear structure information for the neutron-rich actinide nuclei is important since it is the benchmark for theoretical models that provide predictions for the heaviest nuclei. Purpose: gamma-ray spectroscopy of neutron-rich heavy nuclei in the actinide region. Method: Multinucleon-transfer reactions in Zn-70 + U-238 and Xe-136 + U-238 have been measured in two experiments performed at the INFN Legnaro, Italy. In the Zn-70 experiment the high-resolution HPGe Clover Array (CLARA) coupled to the magnetic spectrometer PRISMA was employed. In the Xe-136 experiment the high-resolution Advanced Gamma Tracking Array (AGATA) was used in combination with PRISMA and the Detector Array for Multinucleon Transfer Ejectiles (DANTE). Results: The ground-state band (g.s. band) of U-240 was measured up to the 20(+) level and a tentative assignment was made up to the (24(+)) level. Results from gamma gamma coincidence and from particle coincidence analyses are shown. Moments of inertia (MoI) show a clear upbend. Evidence for an extended first negative-parity band of U-240 is found. Conclusions: A detailed comparison with latest calculations shows best agreement with cranked relativistic Hartree-Bogoliubov (CRHB) calculations for the g.s. band properties. The negative-parity band shows the characteristics of a K-pi = 0 band based on an octupole vibration.

R. Chapman et al.; 17 pags.; 18 figs.; 1 tab.; PACS number(s): 23.20.Lv, 25.70.Lm, 27.30.+t

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 Xe-136 + U-238 have been measured in a high-resolution gamma-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 gamma-ray spectroscopy is feasible for few-neutron transfer channels in U and the -2p channel populating Th isotopes.

The implementation of a Teleconsultation service in the primary health care is a great challenge. This work presents the effort made in the Espirito Santo Telehealth Project to consolidate the teleconsultation service. The impact of each strategy made was evaluated in terms of the number of teleconsultations produced. The combination of periodic visits and the promotion of local workshops were responsible for a sustainable use of the service for the last six months.

Expérience GANIL/VAMOS/EXOGAM; International audience; Absolute cross sections for isotopically identified products formed in multinucleon transfer in the136Xe + 198Pt system at ∼ 8 MeV=nucleon are reported. The isotopic distributions obtained using a largeacceptance spectrometer demonstrated the production of the “hard-to-reach” neutron-rich isotopes forZ < 78 around the N = 126 shell closure far from stability. The main contribution to the formation of theseexotic nuclei is shown to arise in collisions with a small kinetic energy dissipation. The presentexperimental finding corroborates for the first time recent predictions that multinucleon transfer reactionswould be the optimum method to populate and characterize neutron-rich isotopes around N = 126 whichare crucial for understanding both astrophysically relevant processes and the evolution of “magic” numbersfar from stability.

Measurements of fusion excitation functions of Ni-58 + Sn-124 and Ni-64 + Sn-124 are extended towards lower energy to cross sections of 1 mu b and are compared to detailed coupled-channels calculations. The calculations clearly show the importance of including transfer reactions in a coupled-channels treatment for such heavy systems. This result is different from the conclusion made in a previous article which claimed that the influence of transfer on fusion is not important for fusion reactions of Ni + Sn. In the energy region studied in this experiment no indication of fusion hindrance has been observed, which is consistent with a systematic study of this behavior.