Data for the angular distribution of the inclusive 7 Be production cross section in the 8 B + 208 Pb system at an incident energy of 50 MeV, equivalent to the nominal Coulomb barrier height, were measured at the CRIB facility. A coupled discretized continuum channel calculation was able to describe the data well, with no evidence for a significant contribution from nonelastic breakup. The energy dependence of the breakup cross section was investigated with the aid of previous measurements of the inclusive 7 Be production cross section for the same system at a deep sub-barrier energy and at approximately four times the Coulomb barrier. We infer an increasing importance of nonelastic breakup as the incident energy is increased above the barrier, ruling out proton-stripping as a possible mechanism for this process due to the increasingly badly Q-matched character of this transfer reaction as the incident energy increases.

One-neutron stripping process between ^6 Li and ^209 Bi was studied at 28, 30, and 34 MeV using the in-beam γ -ray spectroscopy method. The γ – γ coincident analysis clearly identified two γ -rays feeding the ground and long-lived isomeric states, which were employed to determine the cross section. The one-neutron stripping cross sections were similar to the cross sections of complete fusion in the ^6 Li+ ^209 Bi system, but the one-neutron stripping cross sections decreased more gradually at the sub-barrier region. A coupled-reaction-channel calculation was performed to study the detailed reaction mechanism of the one-neutron stripping process in ^6 Li. The calculations indicated that the first excited state of ^5 Li is critical in the actual one-neutron transfer mechanism, and the valence proton of ^209Bi can be excited to the low-lying excited state in ( ^6Li , ^5Li ) reaction, unlike in the (d,p) reaction.

The complete and incomplete fusion cross sections for Li-6+Bi-209 were measured using the in-beam gamma-ray method around the Coulomb barrier. The cross sections of (deuteron captured) incomplete fusion (ICF) products were re-quantified experimentally for this reaction system. The results reveal that the ICF cross section is equivalent to that of complete fusion (CF) above the Coulomb barrier and dominant near or below the Coulomb barrier. A theoretical calculation based on the continuum discretized coupled channel (CDCC) method was performed for the aforementioned CF and ICF cross sections; the result is consistent with the experiments. The universal fusion function (UFF) was also compared with the measured CF cross section for different barrier parameters, demonstrating that the CF suppression factor is significantly influenced by the choice of potential, which can reflect both dynamic and static effects of breakup on the fusion process.

Astrophysical reactions involving radioactive isotopes (RI) often play an important role in high-temperature stellar environments. The experimental studies on the reaction rates for those are still limited mainly due to the technical difficulties in producing high-quality RI beams. A direct measurement of those reactions would be still challenging in many cases, however, we can make a reliable evaluation of the reaction rates by an indirect method or by studying the resonance prorerties. Here we ntroduce recent examples of experimental studies on such RI-involving astrophysical reactions, performed at Center for Nuclear Study, the University of Tokyo, using the low-energy RI beam separator CRIB. One is for the neutron-induced destruction reactions of 7Be in the Big-Bang nucleosynthesis, and the other is the study on the 22Mg(α, p) reaction relevant in X-ray bursts, which was performed with the resonant scattering method from the inverse reaction channel.

The excitation of the dynamical dipole mode was explored in the formation of a heavy composite system with mass A similar or equal to 190, by investigating its fission channel. The composite system was produced through the charge asymmetric reaction, Ca-40 + Sm-152, and the nearly charge symmetric one, Ca-48 + Sm-144, at E-lab = 11 and 10.1 MeV/nucleon, respectively. High-energy gamma rays and light charged particles were detected in coincidence with the two fission fragments by means of the MEDEA multidetector array coupled to two parallel plate avalanche counters. The kinetic energy spectra of the light charged particles measured at different angles were used to infer the average excitation energy, the average mass, and the average charge of the produced nuclei whereas the time of flight and the emission angle of the fragments were employed to reconstruct the fission dynamics. The study of the gamma-ray spectra and angular distributions for the selected fission events, allowed us to establish (i) the excitation of the giant dipole resonance in the composite system of both reactions and (ii) the excitation of the dynamical dipole mode in the dinucleus of the charge asymmetric reaction by isolating its prompt gamma radiation through the difference technique. The present results on the dynamical dipole mode were compared with the experimental findings for the evaporation channel of the Ca-40 + Sm-152 reaction and moreover with calculations based on a collective bremsstrahlung analysis of the reaction dynamics. Interesting hints connecting the dynamical dipole gamma radiation with the superheavy element quest are given.

The excitation of the dynamical dipole mode was explored in the formation of a heavy composite system with mass $A\ensuremath{\simeq}$ 190, by investigating its fission channel. The composite system was produced through the charge asymmetric reaction, $^{40}\mathrm{Ca} + ^{152}\mathrm{Sm}$, and the nearly charge symmetric one, $^{48}\mathrm{Ca} +^{144}\mathrm{Sm}$, at ${E}_{\text{lab}}$ = 11 and 10.1 MeV/nucleon, respectively. High-energy $\ensuremath{\gamma}$ rays and light charged particles were detected in coincidence with the two fission fragments by means of the MEDEA multidetector array coupled to two parallel plate avalanche counters. The kinetic energy spectra of the light charged particles measured at different angles were used to infer the average excitation energy, the average mass, and the average charge of the produced nuclei whereas the time of flight and the emission angle of the fragments were employed to reconstruct the fission dynamics. The study of the $\ensuremath{\gamma}$-ray spectra and angular distributions for the selected fission events, allowed us to establish (i) the excitation of the giant dipole resonance in the composite system of both reactions and (ii) the excitation of the dynamical dipole mode in the dinucleus of the charge asymmetric reaction by isolating its prompt $\ensuremath{\gamma}$ radiation through the difference technique. The present results on the dynamical dipole mode were compared with the experimental findings for the evaporation channel of the $^{40}\mathrm{Ca} + ^{152}\mathrm{Sm}$ reaction and moreover with calculations based on a collective bremsstrahlung analysis of the reaction dynamics. Interesting hints connecting the dynamical dipole $\ensuremath{\gamma}$ radiation with the superheavy element quest are given.

The dynamics of a nuclear open quantum system could be revealed in the correlations between the breakup fragments of halo nuclei. The breakup mechanism of a proton halo nuclear system is of particular interest as the Coulomb polarization may play an important role, which, however, remains an open question. Here we use a highly efficient silicon detector array and measure the correlations between the breakup fragments of 8B incident on 120Sn at near-barrier energies. The energy and angular correlations can be explained by a fully quantum mechanical method based on the state-of-the-art continuum discretized coupled channel calculations. The results indicate that, compared to the neutron halo nucleus 6He, 8B presents distinctive reaction dynamics: the dominance of the elastic breakup. This breakup occurs mainly via the short-lived continuum states, almost exhausts the 7Be yield, indicating the effect of Coulomb polarization on the proton halo state. The correlation information reveals that the prompt breakup mechanism dominates, occurring predominantly on the outgoing trajectory. We also show that, as a large environment, the continuum of 8B breakup may not significantly influence elastic scattering and complete fusion.

The cosmological lithium problem (CLP) stems from the outstanding discrepancy between theoretical predictions and astronomical observations of primordial lithium abundances. For the radiogenic production of 7 Li, 7 Be plays a pivotal role in the Big Bang nucleosynthesis (BBN). Nevertheless, the data for neutron-induced 7 Be destruction processes were still sparse, and especially lacked information on the contributions of transitions to the 7 Li excited states. In this work, we have determined the 7 Be ( n , p 0 ) 7 Li, 7 Be ( n , p 1 ) 7 Li*, and 7 Be ( n , α ) 4 He reaction cross sections by means of the Trojan Horse method. The present and the previous data were analyzed together by a multichannel R -matrix fit, providing an improved uncertainty evaluation of the ( n , p 0 ) channel and the first-ever quantification of the ( n , p 1 ) contribution in the BBN-relevant energy range. We implemented the revised total reaction rate summing both the ( n , p 0 ) and ( n , p 1 ) contributions in a state-of-the-art BBN code PRIMAT . As a consequence, the present nuclear-physics data offers a reduction of the predicted 7 Li abundance by about one-tenth, which would impose a stricter constraint on BBN and head us in the correct direction to the CLP solution.

The exclusive breakup of the Borromean nucleus Be-9 incident on a proton target at 5.67 MeV/nucleon was studied with a triple coincidence requirement between the two breakup a fragments and the recoiling proton. The analysis was performed using an event-by-event code in a full kinematics approach, and Q-value spectra, relative spectra, and energy spectra of all reaction products were determined. Clear signatures of the three breakup modes: alpha + alpha + n, Be-8 + n, and He-5 + He-4 were observed in the recoiling proton spectra and the rates of these modes were quantified.

A detailed comparative study of the sub-barrier fusion of the two near-by systems 36 S + 50 Ti, 51 V was performed at the National Laboratories of Legnaro (INFN).We aimed to investigate 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.The comparison of the exctiation functions and barrier distributions highlighted a very similar behavior, down to the level of 20 -30 µb.Coupled-channels calculations have been performed including the low energy excitations of both projectile and targets and the results are in very good agreement with the data.This indicates that the low-lying levels in 51 V can be interpreted in the weak-coupling scheme and that the extra proton in the f 7/2 shell does not have a significant influence on sub-barrier fusion.

The mechanism of reactions with weakly-bound proton-rich nuclei at energies near the Coulomb barrier is a long-standing open question owing to the paucity of experimental data. In this study, a complete kinematics measurement was performed for the proton drip-line nucleus 17F interacting with 58Ni at four energies near the Coulomb barrier. Thanks to the powerful performance of the detector array, exhaustive information on the reaction channels, such as the differential cross sections for quasielastic scattering, exclusive and inclusive breakup, as well as for fusion-evaporation protons and alphas, was derived for the first time. The angular distributions of quasielastic scattering and exclusive breakup can be described reasonably well by the continuum-discretized coupled-channels calculations. The inclusive breakup was investigated using the three-body model proposed by Ichimura, Austern, and Vincent, and results indicate the non-elastic breakup is the dominant component. The total fusion cross sections were determined by the fusion-evaporation protons and alphas. Based on the measured exclusive breakup data, the analysis of the classical dynamical simulation code PLATYPUS demonstrates that the incomplete fusion plays a minor role. Moreover, compared with 16O+58Ni, both the reaction and total fusion cross sections of 17F+58Ni exhibit an enhancement in the sub-barrier energy region, which mainly arises from couplings to the continuum states. This work indicates that the information of full reaction channels is crucially important to comprehensively understand the reaction mechanisms of weakly bound nuclear systems.

The elastic scattering process for the nuclear reactions induced by the Radioactive Ion Beams 7 Be and 8 B on a 208 Pb target was measured for the first time in the energy range around the Coulomb barrier. Extensive theoretical calculations within the framework of the optical model were performed. An excellent agreement between experimental data and theoretical predictions was achieved for the reaction 7 Be + 208 Pb, while a comprehensive understanding of the reaction dynamics induced by the more exotic projectile 8 B is still far to be reached. Predictions of the cross section for the breakup for both systems will also be given.

Level structures of Rn-212 have been studied by in-beam gamma-ray spectroscopic methods using the Bi-209(Li-6, 3n)Rn-212 reaction at beam energies of 28, 30, and 34 MeV. A number of new nonyrast states based on pi h(9/2)(4) and pi h(9/2)J(7/2) configurations have been identified. A 3((-)) collective state is also proposed at 2121 keV, which is most likely formed by mixing the octupole vibration with the 3(-) member of the pi h(9/2)(3)i(13/2) multiplet. The level scheme is compared with large-scale shell model calculations and discussed in terms of excitations of valence protons and without contributions from the Pb-208 core. An overall excellent agreement is obtained for states that can be described in this model space.

Light charged particles emitted by the compound nucleus Er-158 produced in the reaction S-32 (180 MeV) Te-126, at the excitation energy E-x = 92 MeV, have been measured at Laboratori Nazionali di Legnaro in coincidence with fission fragments and evaporation residues. The 4 pi detector array 87rLP coupled to a system of parallel-plate avalanche counters to detect evaporation residues has been used. Data have been analyzed in the framework of the statistical model of evaporation with the code PACE2_N11. This enlarged version of the code PACE2 has been used to reproduce the large set of observables measured in the fusion-evaporation and fusion-fission channels along with experimental prescission neutron multiplicity and fission cross section taken from literature. It is found that the simultaneous reproduction of the prescission neutron, proton, and alpha-particle multiplicities can be obtained with zero fission delay without dynamical effects. However, the same set of model input parameters does not allow us to reproduce proton and alpha-particle multiplicities in the evaporation channel. Extensive calculations, with different sets of parameters, show the limits of the statistical model in reproducing the whole set of data. This work evidences the importance of measuring a large set of observables in order to obtain a reliable description of the decay of the compound nucleus, and in particular of the fission process.

The breakup of 9 Be is studied via an inelastic scattering experiment on a proton target at 5.6 A MeV in inverse kinematics. Two of the three cluster constituents ( α and α ) as well as the proton target recoil were recorded in a triple coincidence mode allowing a full kinematics approach analysis. In this respect relative α - α and α - n, Q-value and 9 Be excitation spectra, energy spectra for all fragments as well as the energy spectrum of the recoil proton were reconstructed. A clear signature of the two breakup sequential modes ( 5 He + 4 He and 8 Be + n) was identified via the recoiling proton reconstructed spectra together with the direct breakup decay. A strong 5 He + 4 He mode was observed compatible with previous beta decay experiments.

The overlap in the mass symmetric region of the reaction products from fusion-fission and quasifission complicates the assignment of symmetric events to complete fusion on the basis of the mass distribution alone. Additional observables, besides mass distribution, should be used. The approach proposed here relies on the fact that fusion-fission and quasifission are characterized by different timescales. Within this framework, we performed a detailed study to find out how timescales can be probed via angular momentum transfer as measured via gamma-ray multiplicities. The proof of principle was carried out by measuring the gamma rays in coincidence with fusion-fission and quasielastic binary fragments in the reaction S-32 + Au-197 at beam energy near the Coulomb barrier. The experiment was performed at the Accelerateur Lineaire Tandem a Orsay (ALTO) facility at the Institut De Physique Nucleaire (IPN) in Orsay (France) using a detection setup consisting of ORGAM (ORsay GAMma) and PARIS (Photon Array Radioactive Ion Stable beams) gamma-detectors arrays coupled with the CORSET (CORrelation SETup) time-of-flight spectrometer. Results of the sensitivity of this method to distinguish reaction channels with different dynamics are discussed.

We performed indirect measurements of the neutron-induced reactions \(^{7}\)Be(n,p)\(^{7}\)Li and \(^{7}\)Be(n,\(\mathsf \alpha \))\(^{4}\)He simultaneously by the Trojan Horse method relevant to the cosmological \(^7\)Li problem. Preliminary excitation functions for \((n,p_0)\) and \((n,\alpha )\) are basically consistent with the previous studies, and new information about the \((n,p_1)\) contribution suggests possible enhancement of the total reaction rate.