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Elastic scattering and transfer cross sections for the $^{7}\mathrm{Be}+^{9}\mathrm{Be}$ system have been measured at ${E}_{\mathrm{lab}}=23.1\phantom{\rule{0.28em}{0ex}}\mathrm{MeV}$ using the $^{7}\mathrm{Be}$ radioactive secondary beam produced at Radioactive Ion Beams in Brazil facility at the University of S\~ao Paulo. The elastic scattering has been measured by detecting the $^{7}\mathrm{Be}$ scattered at forward angles in the laboratory system. The transfer reaction $^{9}\mathrm{Be}(^{7}\mathrm{Be},^{9}\mathrm{Be})^{7}\mathrm{Be}$ was identified by detecting the $^{9}\mathrm{Be}$ scattered at the same laboratory angles. The elastic angular distribution has been analyzed by optical model calculations using a Woods-Saxon form factor whose parameters have been varied to best reproduce the experimental data at forward angles. Coupled reaction channels calculations (CRC) have been performed to describe the transfer, considering the coupling to the transfer channel and including contributions to the ground state and to the first excited state of $^{7}\mathrm{Be}(1/2\ensuremath{-};429\phantom{\rule{0.16em}{0ex}}\mathrm{keV}$) in the final state. The spectroscopic amplitudes used in the CRC calculation have been derived from shell-model calculations. Similar CRC calculations were applied to existing $^{9}\mathrm{Be}(p,t)^{7}\mathrm{Be}$ data to check the consistency of our results results for the ($^{7}\mathrm{Be},^{9}\mathrm{Be}$) transfer reaction.

In this work, we study the effect of paring correlation on the two-neutron transfer reaction \(^{28}\)Si(\(^{18}\)O,\(^{16}\)O)\(^{30}\)Si at 84 MeV incident energy in the laboratory frame. For this, coupled reaction channel (CRC) and coupled channel Born approximation (CCBA) calculations were performed considering the cluster, independent coordinates and sequential transfer models for two-neutron transfer. For the calculation of the spectroscopic amplitudes the NuShellX (http://www.garsington.eclipse.co.uk/, [1]) code was used.

Background: Recently, a systematic exploration of two-neutron transfer induced by the $(^{18}\mathrm{O},\phantom{\rule{0.16em}{0ex}}^{16}\mathrm{O})$ 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 $(^{18}\mathrm{O},\phantom{\rule{0.16em}{0ex}}^{17}\mathrm{O})$ reaction on $^{16}\mathrm{O},\phantom{\rule{0.28em}{0ex}}^{28}\mathrm{Si}$, and $^{64}\mathrm{Ni}$ 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 $^{18}\mathrm{O}+^{16}\mathrm{O}$ and the $^{18}\mathrm{O}+^{28}\mathrm{O}$ systems, we used two interactions in the shell model. The experimental angular distributions are reasonably well reproduced by the CRC calculations. In the $^{18}\mathrm{O}+^{64}\mathrm{Ni}$ 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 $^{18}\mathrm{O}+^{16}\mathrm{O}$ and $^{18}\mathrm{O}+^{64}\mathrm{Ni}$ systems.

In this paper, we analyze the one-neutron pick-up from the 55Mn target when it is bombarded by 17MeV deuteron, by performing coupled reaction channel (CRC) calculations. Spectroscopic amplitudes for CRC calculations, and structural information such as reduced B(E2) transition probabilities, quadrupole, and magnetic momenta, are obtained from shell-model calculations using the fp-kb3 interaction. The calculated structure quantities are in good agreement with the available experimental data for both target and ejectile. Analyses of angular distributions show the relevance of microscopic information for the description of the higher excited states of 54Mn .

In this work we study the simultaneous and sequential two-neutron transfer mechanisms to the $^{28}\mathrm{Si}$ nucleus induced by $(t,p)$ and $(^{18}\mathrm{O},^{16}\mathrm{O})$ reactions. New experimental cross sections for the $^{28}\mathrm{Si}(^{18}\mathrm{O},^{16}\mathrm{O})^{30}\mathrm{Si}$ 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 $1{p}_{3/2}, 1{p}_{1/2}, 1{d}_{3/2}, 1{d}_{5/2}$, and $2{s}_{1/2}$ 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 $^{30}\mathrm{Si}$. A systematic analysis of the two-neutron transfer induced by the $(^{18}\mathrm{O},^{16}\mathrm{O})$ reaction indicates that the static deformation of target nuclei impacts the two-neutron transfer mechanism.

The measurement of one-neutron stripping cross sections for the $^{89}\mathrm{Y}(^{6}\mathrm{Li},^{5}\mathrm{Li})^{90}\mathrm{Y}^{*}$ reaction at 22 MeV and 34 MeV is reported, using both in-beam and off-beam $\ensuremath{\gamma}$-ray spectroscopy methods. Characteristic $\ensuremath{\gamma}$ lines of $^{90}\mathrm{Y}$ are clearly identified by both the $\ensuremath{\gamma}\text{\ensuremath{-}}\ensuremath{\gamma}$ and proton-$\ensuremath{\gamma}$ coincidence methods. The obtained cross section of one-neutron stripping at 34 MeV is found to be much smaller than that at 22 MeV. The one-neutron stripping cross sections measured for this system have the same order of magnitude as the one measured for the same reaction for the $^{6}\mathrm{Li}+^{96}\mathrm{Zr}$ system at energies around the Coulomb barrier. Parameter-free coupled reaction channel calculations agree quite well with the experimental data. Theoretical study of the effect of the one-neutron transfer on the elastic total fusion cross section is performed.

Recently, various two-neutron transfer studies using the $(^{18}\mathrm{O},^{16}\mathrm{O})$ 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 $^{18}\mathrm{O}+^{64}\mathrm{Ni}$ system at 84 MeV incident energy, to the ground and first ${2}^{+}$ excited state of the residual $^{66}\mathrm{Ni}$ 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 $^{66}\mathrm{Ni}$, the direct transfer is the dominant reaction mechanism, whereas for the transfer to the first excited state of $^{66}\mathrm{Ni}$, 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.

Background: In our recent work [M. J. Ermamatov et al., Phys. Rev. C 94, 024610 (2016)], the two-neutron transfer induced by the $(^{18}\mathrm{O},^{16}\mathrm{O})$ reaction was studied for $^{16}\mathrm{O}$ nucleus. Theoretical analysis of the low-lying states of $^{18}\mathrm{O}$ 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 $^{18}\mathrm{O}$ nucleus. In order to achieve a comprehensive picture, we revisit the experimental data for the $^{16}\mathrm{O}(t,p)^{18}\mathrm{O}$ reaction at 15 MeV bombarding energy. We also include new experimental cross sections for the high-lying states of the $^{18}\mathrm{O}$ residual nucleus, populated in the $^{16}\mathrm{O}(^{18}\mathrm{O},^{16}\mathrm{O})^{18}\mathrm{O}$ 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 $^{18}\mathrm{O}$ 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 $^{16}\mathrm{O}(t,p)^{18}\mathrm{O}$ data well, leading to natural parity states in the $^{18}\mathrm{O}$ nucleus without the need of adjustable parameters. The same methods are applied to the $^{16}\mathrm{O}(^{18}\mathrm{O},^{16}\mathrm{O})^{18}\mathrm{O}$ 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.

The $^{13}\mathrm{C}(^{18}\mathrm{O},^{16}\mathrm{O})^{15}\mathrm{C}$ 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.

Recently a quantitative description of the two-neutron transfer reaction $^{12}\mathrm{C}(^{18}\mathrm{O},^{16}\mathrm{O})^{14}\mathrm{C}$ 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 ($^{18}\mathrm{O},^{16}\mathrm{O}$) reactions to assess pair configurations in nuclear states. In this work we apply this methodology to the $^{16}\mathrm{O}(^{18}\mathrm{O},^{16}\mathrm{O})^{18}\mathrm{O}$ reaction at 84 MeV. Experimental angular distributions for the two-neutron transfer to the ground state and ${2}_{1}^{+}$ state of $^{18}\mathrm{O}$ 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.