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The 13C(18O,16O)15C reaction is studied at 84 MeV incident energy. Excitation energy spectra and absolute cross-section angular distributions for the strongest transitions are measured with good energy and angular resolutions. Strong selectivity for two-neutron configurations in the states of the residual nucleus is found. The measured cross-section angular distributions are analyzed by exact finite-range coupled reaction channel calculations. The two-particle wave functions are extracted using the extreme cluster and the independent coordinate scheme with shell-model derived coupling strengths. A new approach also is introduced, the microscopic cluster, in which the spectroscopic amplitudes in the center-of-mass reference frame are derived from shell-model calculations using the Moshinsky transformation brackets. This new model is able to describe well the experimental cross section and to highlight cluster configurations in the involved wave functions. [ABSTRACT FROM AUTHOR]

Recently, the bound and continuum spectrum of 11Be has been calculated within the ab initio no-core shell model with continuum (NCSMC) method, with the parity inversion in the ground state successfully reproduced. The continuum spectrum obtained is in agreement with known experimental levels. The S matrix contained in the NCSMC continuum wave functions of the n+10Be system is used in this work for the first time in a transfer-to-the-continuum (TC) reaction calculation. The TC approach is applied to study the excitation energy spectrum of 11Be measured in the 9Be(18O,16O)11Be reaction at 84 MeV. Previously known levels are confirmed and theoretical and experimental evidence for a 9/2+ state at Ex=5.8 MeV is given, whose configuration is thought to be 10Be(2+)+n(d5/2). [ABSTRACT FROM AUTHOR]

The nuclear scattering at energies well above the Coulomb barrier allows for a fairly sensitive examination of the parameters of the optical potential when the relevant couplings are included into the calculations. In this work we present experimental angular distribution data for the elastic and inelastic scatterings of 16O impinging on 27Al and 28Si target nuclei at Elab=240MeV. The experimental data were measured at 7∘<θc.m.<16∘ with good angular resolution. Experimental data are compared with coupled channel calculations with the inclusion of couplings to excited states in the target and projectile. We show that the shape of angular distributions are sensitive to the mass diffuseness parameter and the best agreement is achieved for a=0.62fm. [ABSTRACT FROM AUTHOR]

Background: Recently, a systematic exploration of two-neutron transfer induced by the (18O,16O) reaction on different targets has been performed. The high-resolution data have been collected at the MAGNEX magnetic spectrometer of the INFN-LNS Laboratory in Catania and analyzed with the coupled reaction channel (CRC) approach. The simultaneous and sequential transfers of the two neutrons have been considered under the same theoretical framework without the need for adjustable factors in the calculations. Purpose: A detailed analysis of the one-neutron transfer cross sections is important to study the sequential two-neutron transfer. Here, we examine the (18O,17O) reaction on 16O,28Si, and 64Ni targets. These even-even nuclei allow for investigation of one-neutron transfer in distinct nuclear shell spaces. Method: The MAGNEX spectrometer was used to measure mass spectra of ejectiles and extract differential cross sections of one-neutron transfer to low-lying states. We adopted the same CRC formalism used in the sequential two-neutron transfer, including relevant channels and using spectroscopic amplitudes obtained from shell-model calculations. We also compare with the one-step distorted-wave Born approximation (DWBA). Results: For the 18O+16O and the 18O+28O systems, we used two interactions in the shell model. The experimental angular distributions are reasonably well reproduced by the CRC calculations. In the 18O+64Ni system, we considered only one interaction, and the theoretical curve describes the shape and order of magnitude observed in the experimental data. Conclusions: Comparisons between experimental DWBA and CRC angle-integrated cross sections suggest that excitations before or after the transfer of a neutron are relevant in the 18O+16O and 18O+64Ni systems. [ABSTRACT FROM AUTHOR]

In this work we study the simultaneous and sequential two-neutron transfer mechanisms to the 28Si nucleus induced by (t,p) and (18O,16O) reactions. New experimental cross sections for the 28Si(18O,16O)30Si reaction at 84 MeV are also presented. Direct reaction calculations are carried out within the exact finite range coupled reaction channel, for the simultaneous transfer of the two-neutron cluster, and the second-order distorted wave Born approximation, for the sequential transfer. Two different models are considered to describe the two-neutron cluster. The spectroscopic information was obtained from a shell-model calculation with a psdmod interaction for the target overlaps where the 1p3/2, 1p1/2, 1d3/2, 1d5/2, and 2s1/2 orbitals are included as valence subspace. We show that simultaneous and sequential two-neutron transfers are competing mechanisms for the population of the ground state in 30Si. A systematic analysis of the two-neutron transfer induced by the (18O,16O) reaction indicates that the static deformation of target nuclei impacts the two-neutron transfer mechanism. [ABSTRACT FROM AUTHOR]

The elastic scattering angular distribution of the 16O+60Ni system at 260 MeV was measured in the range of the Rutherford cross section down to seven orders of magnitude. The cross sections of the lowest 2+ and 3- inelastic states of the target were also measured over several orders of magnitude. Coupled-channel (CC) calculations were performed and are shown to be compatible with the whole set of data only when including the excitation of the projectile and when the deformations of the imaginary part of the nuclear optical potential are taken into account. Similar results were obtained when the procedure is applied to the existing data on 16O+27Al elastic and inelastic scattering at 100 and 280 MeV. An analysis in terms of dynamical polarization potentials (DPP) indicates the major role of coupled-channel effects in the overlapping surface region of the colliding nuclei. [ABSTRACT FROM AUTHOR]

Recently, various two-neutron transfer studies using the (18O,16O) reaction were performed with a large success. This was achieved because of a combined use of the microscopic quantum description of the reaction mechanism and of the nuclear structure. In the present work we use this methodology to study the two-neutron transfer reaction of the 18O+64Ni system at 84 MeV incident energy, to the ground and first 2+ excited state of the residual 66Ni nucleus. All the experimental data were measured by the large acceptance MAGNEX spectrometer at the Instituto Nazionale di Fisica Nucleare-Laboratori Nazionali del Sud (Italy). We have performed exact finite range cross section calculations using the coupled channel Born approximation (CCBA) and coupled reaction channel (CRC) method for the sequential and direct two-neutron transfers, respectively. Moreover, this is the first time that the formalism of the microscopic interaction boson model (IBM-2) was applied to a two-neutron transfer reaction. From our results we conclude that for two-neutron transfer to the ground state of 66Ni, the direct transfer is the dominant reaction mechanism, whereas for the transfer to the first excited state of 66Ni, the sequential process dominates. A competition between long-range and short-range correlations is discussed, in particular, how the use of two different models (Shell model and IBM's) help to disentangle long- and short-range correlations. [ABSTRACT FROM AUTHOR]

Background: In our recent work [M. J. Ermamatov et al., Phys. Rev. C 94, 024610 (2016)], the two-neutron transfer induced by the (18O,16O) reaction was studied for 16O nucleus. Theoretical analysis of the low-lying states of 18O indicates that the transfer to the ground state proceeds predominantly through simultaneous transfer of the two-neutron system. Purpose: In this work, we extend our previous theoretical analysis towards high-lying states of the 18O nucleus. In order to achieve a comprehensive picture, we revisit the experimental data for the 16O(t,p)18O reaction at 15 MeV bombarding energy. We also include new experimental cross sections for the high-lying states of the 18O residual nucleus, populated in the 16O(18O,16O)18O reaction at 84 MeV. Method: The same spectroscopic parameters of the target nucleus were used as input in the coupled channel calculations for the transfer induced by triton and 18O projectiles. Simultaneous two-neutron transfer is calculated within the coupled reaction channel approach, using the extreme cluster and independent coordinate models. The sequential process is calculated within the distorted-wave Born approximation. Results: Theoretical calculations reproduce the 16O(t,p)18O data well, leading to natural parity states in the 18O nucleus without the need of adjustable parameters. The same methods are applied to the 16O(18O,16O)18O data and a good agreement is observed. Conclusions: Detailed analyses show the importance of a simultaneous mechanism for the two-neutron transfer reactions. In transferring two neutrons, the pairing correlation plays an important role. [ABSTRACT FROM AUTHOR]

The complete set of open channels for the 7Li+p system, namely elastic scattering, inelastic scattering, breakup, the 7Li+p→7Be+n charge exchange reaction, and the 7Li+p→4He+4He reaction, was measured in the same experiment in inverse kinematics at an energy of 5.44 MeV/u. Data were also obtained for the charge exchange reaction at energies of 5.0 and 3.57 MeV/u. The elastic and inelastic scattering and breakup data were reported previously and are reviewed here and, together with the new data for the other two reactions, are discussed coherently within the same continuum-discretized coupled-channels model framework. [ABSTRACT FROM AUTHOR]

An exclusive measurement of the breakup of 7Li incident on a proton target was performed at 38.1 MeV (5.44 MeV/nucleon), probing the direct part of the excitation to the continuum. The two cluster constituents of 7Li, 4He, and ³H, were recorded in coincidence in the MAGNEX spectrometer and a silicon detector respectively. Both detection systems were set at forward angles and the measurement of both kinematical solutions allowed the determination of a breakup angular distribution over a wide angular range in the center-of-mass frame. Comprehensive simulations provided the detection efficiency of the system and via the appropriate kinematics the transformation of the cross sections from the laboratory to the center-of-mass reference frame. The experimental results are analyzed and discussed together with previous elastic scattering data using the Continuum Discretized Coupled Channels (CDCC) framework and are found to be in satisfactory agreement. It was found that while the breakup cross section was dominated by the nonresonant component, the most important influence on the elastic scattering was due to coupling to the 7/2- resonance of 7Li. [ABSTRACT FROM AUTHOR]

Recently a quantitative description of the two-neutron transfer reaction 12C(18O, 16O)14C was performed and the measured cross sections were successfully reproduced [M. Cavallaro et al., Phys. Rev. C 88, 054601 (2013)]. This task was accomplished by combining nuclear structure calculations of spectroscopic amplitudes and a full quantum description of the reaction mechanism. Verification of such a theoretical approach to other heavy nuclear systems is mandatory in order to use (18O, 16O) reactions to assess pair configurations in nuclear states. In this work we apply this methodology to the 16O(18O, 16O)18O reaction at 84 MeV. Experimental angular distributions for the two-neutron transfer to the ground state and 2+1 state of 18O were obtained using the MAGNEX spectrometer at INFN-LNS. The roles of one- and two-step processes are analyzed under the exact finite range coupled reaction channel and the second order distorted wave Born approximation. We conclude that the one-step transfer mechanism is dominant in this system. [ABSTRACT FROM AUTHOR]

Elastic scattering measurements were performed for the 7Li+p system in inverse kinematics at energies of 16, 25, 35, and 38.1 MeV and for the 7Li+d system at 38.1 MeV. The heavy ejectiles were detected by the large acceptance MAGNEX spectrometer at the Laboratori Nazionali del Sud in Catania, Italy. The results are analyzed using the Jeukenne-Lejeune-Mahaux and continuum discretized coupled channel frameworks. In the latter case the cluster structure of 7Li proves to be critical for the theoretical interpretation of the experimental results. [ABSTRACT FROM AUTHOR]

The neutron decay of the resonant states of light neutron-rich nuclei is an important and poorly explored property, useful to extract valuable nuclear structure information. In the present paper the neutron decay of the 15C resonances populated via the two-neutron transfer reaction 13C(18O,16On) at 84-MeV incident energy is reported for the first time using an innovative technique which couples the MAGNEX magnetic spectrometer and the EDEN neutron detector array. Experimental data show that the resonances below the one-neutron emission threshold decay to the 14C ground state via one-neutron emission with an almost 100% total branching ratio, whereas the recently observed 15C giant pairing vibration at 13.7 MeV mainly decays via two-neutron emission. [ABSTRACT FROM AUTHOR]