Table of contents

Fragmentation reactions constitute an optimum tool for exploring the nuclear landscape by producing nuclei far from stability at in-flight radioactive nuclear beam facilities. Moreover, they are routinely used in modern cancer therapy treatments. Nevertheless, the large dynamical and isospin range covered by this reaction mechanism are unique features for many fundamental studies. In this work we review some of the most salient recent results in fundamental nuclear physics studies based on fragmentation reactions.

The exact treatment of nuclei starting from the constituent nucleons and the fundamental interactions among them has been a long-standing goal in nuclear physics. Above all nuclear scattering and reactions, which require the solution of the many-body quantum-mechanical problem in the continuum, represent a theoretical and computational challenge for ab initio approaches. After a brief overview of the field, we present a new ab initio many-body approach capable of describing simultaneously both bound and scattering states in light nuclei. By combining the resonating-group method (RGM) with the ab initio no-core shell model (NCSM), we complement a microscopic cluster technique with the use of realistic interactions and a microscopic and consistent description of the clusters. We show results for neutron and proton scattering on light nuclei, including p-⁷Be and n-⁸He. We also highlight the first results of the d-³He and d-³H fusion calculations obtained within this approach.

The observation of atomic numbers Z by 40% larger than that of Bi, the heaviest stable element, is an impressive extension in nuclear survival. Although the super heavy nuclei (SHN) are at the limits of Coulomb stability, shell stabilization lowers the ground-state energy, creates a fission barrier, and thereby enables the SHN to exist. The fundamentals of the modern theory concerning the mass limits of nuclear matter have thus obtained experimental verification.

The interaction of exotic nuclei with various targets and implying different types of reactions allows to access a rich variety of information. Some examples of the latest results and recent developments related to some of these reactions are reviewed.

The symmetry energy E_sym is the part of the nuclear energy associated with the asymmetry in the neutron/proton content. Its relevance is due to the role that it plays in a large variety of systems and processes in nuclear structure, astrophysics and heavy-ion collisions dynamics. In the last ten years many efforts from different fields have been pursued to costraint it density dependence both below and above the saturation density(ρ₀ ∼ 0.16fm⁻³). Here we briefly sketch the present status on the knoweledge of E_sym at low density, we discuss the on going work at suprasaturation one and we present new perspective that are opening up for the role of E_sym in the transition to quark matter at high baryon density.

Coulomb breakup at intermediate energies is a useful experimental tool for investigating the microscopic structure of neutron drip-line nuclei. Here, results from the inclusive Coulomb breakup experiment of ³¹Ne on a lead target at RIBF(RI Beam Factory) at RIKEN are presented. The experiment was performed as one of day-one campaign experiments at RIBF, using a ⁴⁸Ca primary beam at 345 MeV/nucleon. A unique feature of a halo nucleus is the enhanced electric dipole strength of the order of 1 W.u.(Weisskopf unit) at very low excitation energies around 1 MeV (soft E1 excitation). Owing to high sensitivity of the Coulomb breakup to the soft E1 excitation, a measurement of inclusive Coulomb breakup cross section can be used to identify the halo structure of a certain drip-line nucleus. We have indeed observed a strong enhancement of the Coulomb breakup cross section of 540(70) mb for ³¹Ne on Pb at 230 MeV/nucleon, nearly as high as that for the known halo nucleus ¹⁹C, thereby giving evidence of the halo structure in ³¹Ne. The finding of a new halo structure for such a heavy system, compared to the known halo nuclei, is the first step for the understanding of halo phenomena along the neutron drip line towards heavier nuclei. We discuss also the change of shell structure in ³¹Ne, as a nucleus in the island of inversion.

Fragment mass distributions for fission after full momentum transfer were measured in the reactions of ³⁰Si,^34,36S,³¹P,⁴⁰Ar + ²³⁸U at bombarding energies around the Coulomb barrier. Mass distributions change significantly as a function of incident beam energy. The asymmetric fission probability increases at sub-barrier energy. The phenomenon is interpreted as an enhanced quasifission probability owing to orientation effects on fusion and/or quasifission. The evaporation residue (ER) cross sections were measured in the reactions of ³⁰Si +²³⁸U and ³⁴S+ ²³⁸U to obtain information on the fusion probability. In the latter reaction, significant suppression of fusion was implied. This suggests that quasifission has large fraction in the mass-symmetric fission events. The results are supported by a model calculation based on a dynamical calculation using Langevin equation, in which the mass distribution for fusion-fission and quasifission fragments are separately determined.

Recent studies on breakup reactions with the continuum-discretized coupled-channels method are reviewed. The topics covered are: four-body breakup processes for ⁶He induced reaction, dynamical relativistic effects on Coulomb breakup, microscopic description of projectile breakup processes, description of ternary processes (new triple-α reaction rate) and new approach to inclusive breakup processes.

In order to reconstruct the yields of the primary hot fragments at the time of their formation, the neutron multiplicity associated with intermediate mass fragments (IMFs) was determined experimentally using the kinematical focusing of light particles emitted along the direction of each IMF. The reaction system ⁶⁴Zn + ¹¹²Sn has been studied at 40 A MeV. IMFs were isotopically identified with Z up to 18. Neutrons were measured at 16 angles around the direction of the IMFs. The exctrated neutron multiplicities are in good agreement with those calculated AMD+Gemini simulations.

Recent experiments have shown that the multimode approach for describing the fission process leads to some compatibility with the observed results. A systematic analysis of the parameters obtained by fitting the fission-fragment mass distribution to the spontaneous and low-energy data has shown that the values for those parameters present a smooth dependence upon the nuclear mass number. In the present work it is shown that the same parameter-values obtained for low-energy fission can be used to describe intermediate-energy fission results of fragment-mass distributions if one takes into account the appropriate distribution of the fissioning system. To calculate the fission-fragment mass distributions, Monte Carlo simulations are used. This simulation considers a two-step reaction mechanism, namely, an intranuclear cascade providing the compound nucleus followed by a mechanism of competition between particle evaporation and fission. The fission-fragment masses are obtained according to the multimode approach following the Statistical Scission Model. Simulations for fission induced by 660 MeV protons on ²⁴¹Am and ²³⁷Np, and for fission of ²³⁸U induced by photons from Bremsstrahlung with end-point energy of 50 MeV have been performed, and the results have been compared with recent experimental data.

We report on our study of the inclusive electron scattering off ⁴He, where emphasis on the role of three-nucleon forces is given. A detailed analysis of the longitudinal response function R_L(ω, q) is done at different kinematics and theoretical results are compared to available experimental data. Calculation are performed with ab-initio techniques where the full four-body continuum dynamics is considered via the Lorentz integral transform method. At lower momentum transfer (q ≤ 200 MeV/c) three-nucleon forces play an important role and the two three-nucleon force models implemented show differences up to 10%.

The reaction ¹⁹⁷Au + ²³²Th at 7.5 AMeV was studied using the BigSol spectrometer at Texas A&M. Theoretical calculations suggest that this reaction could be used as an alternative method to produce heavy and superheavy elements. During the short interaction time, heavy systems of interacting nucleons are formed and, due to the strong energy dissipation, a large number nucleons can be transferred. The larger the lifetime of the decaying giant system, the larger the possible number of transferred nucleons. Moreover shell effects may help in the formation of heavy nuclei in the region of the island of stability. Reaction products emitted in an angular range from 6 to 16 degrees were collected at the entrance of the BigSol spectrometer and detected at the focal plane using a segmented ionization chamber. Four position sensitive PPAC detectors placed along the ion's flight path were used to track the product trajectories and measure the times of flight. The experimental results are presented and compared with theoretical calculations performed with the Constraint Molecular Dynamics code.

We have measured double differential cross sections (DDX) for emission of hydrogen- and helium-isotopes in the interaction of 175 MeV quasi-monoenergetic neutrons with Fe and Bi using the Medley setup at the The Svedberg Laboratory (Uppsala, Sweden). We compared experimental DDX with calculations with the TALYS code, which includes exciton model and Kalbach systematics; the code fails to reproduce the emission of complex light ions, generally overestimating it. We propose an correction for the application of the Kalbach phenomenological model in the TALYS code by introducing a new energy dependence for the nucleon transfer mechanism in the pre-equilibrium emission region. Our results suggest also evidence for multiple pre-equilibrium emission of composite particles at 175 MeV.

The effect of the system size on a number of traditionally accepted signatures of cluster approximation technique of critical behavior have been examined for projectile multifragmenting systems like Mg at 4.5 AGeV and Kr at 0.95 AGeV. The results obtained from analyzing our experimental data on the fluctuation of size of the largest fragments, reduced variance and the mean value of the second moments of charge distribution provide clear evidences of size effect in terms of the height and position of the peaks of the studied parameters.

The continuum discretised couple-channel model (CDCC) and the dynamical eikonal approximation (DEA) are two state-of-the-art models used to study the breakup of halo nuclei. In this work, we compare them for the breakup of ¹⁵C on Pb at 68AMeV. Excellent agreement is obtained for both energy and angular distributions. Slight discrepancy is observed in the contributions of some partial waves, which might affect other breakup observables, like momentum distributions. The use of relativistic velocity has little effect on the energy distribution, but affects more significantly the angular distribution.

A study of the yields for different reaction channels has been performed at the Catania INFN-LNS laboratory using a ¹⁸O beam on ¹³C and ¹²C targets. The ejectiles have been momentum analyzed by the MAGNEX magnetic spectrometer. The achieved mass resolution (about 1/160) has allowed to identify the reaction products corresponding to different reaction channels. The measured yields show an enhancement of two neutrons transfer channel compared to one. This result demonstrates that the (¹⁸O, ¹⁶O) reaction proceeds mainly by the direct transfer of the neutron pair, with small contributions from second order processes.

We discuss the equivalence of a generalized Fermi breakup model, in which densities of excited states are taken into account, and the microcanonical Statistical Multifragmentation Model used to describe the desintegration of highly excited fragments of nuclear reactions.

In this contribution, an overview of the calculations that can be performed within the Continuum Discretized Coupled Channels (CDCC) approach to analyze deuteron induced reactions is given. First, we briefly remind the CDCC formalism. In the second part, we present an extension of the CDCC formalism which accounts for the target excitations allowing us to determine (d,d') cross sections off deformed nuclei. After the derivation of the coupled equations, we compare some calculated inelastic cross sections with experimental data. Then it is shown that the CDCC formalism can also be a useful tool to determine (d,p) or (d,n) cross sections. We illustrate this point for nuclei with N≈32.

Spallation reactions are generally considered to proceed in two stages: a cascade stage followed by an evaporation stage. Light charged particle (lcp) spectra indicate that such particles are produced by both stages. The mechanism of production in the cascade stage is still not fully understood. Using the improved versions of the Liège Intra-Nuclear Cascade model and of the ABLA evaporation model, we have recently shown that lcp's are presumably produced by some kind of dynamical coalescence process, by which a fast particle of the cascade drags a few other nucleons. In the very recent years, precise measurements of the production of heavier clusters have been performed. We improved and generalized our production models for the heavier clusters, up to A=10 and we reached good agreement with experiment. These results strongly suggest that the dynamical coalescence mechanism applies to heavy clusters. The importance of these data for spallation neutron sources and accelerator-driven systems is underlined.

The collision induced by the three Beryllium isotopes, ^9,10,11Be, on ⁶⁴Zn target were investigated at Ec.m. ≈ 1.4 the Coulomb barrier. Elastic scattering angular distributions were measured for the ^9,10Be collisions whereas, in the ¹¹Be case the quasielastic scattering angular distribution was obtained. A strong damping of the quasielastic cross-section was observed in the ¹¹Be case, especially in the angular range around the Coulomb-nuclear interference peak. In this latter case a large total-reaction cross-section is found, more than a factor of two larger than the ones extracted in the reactions induced by the non-halo Beryllium isotopes. A large contribution to the total-reaction cross-section in the ¹¹Be case could be attributed to transfer and/or break-up events.

The aim of our study is to determine excitation functions for the formation of different reaction products with light ions near the Coulomb barrier and to compare the results with computations according to different reaction mechanisms (compound reactions, direct reactions). In the present study results from experiments with a beam of ⁹Be on a thin Aluminum target below and around the Coulomb barrier are presented. The formation of several reaction products was determined by the characteristic gamma emissions from these nuclei. Excitation functions of the reactions ²⁷Al(⁹Be,⁸Be?2a)²⁸Al, ²⁷Al(⁹Be,2n)³⁴Cl, ²⁷Al(⁹Be,pn)³⁴S and ²⁷Al(⁹Be,a2n)³⁰P with lab energies between 5 and 14 MeV have been determined.

The three-body forces (TBF) effect is known to play an important role on the nuclear saturation property, which can be demonstrated typically in the Brueckner (G-matrix) theory. Recently, we have proposed new complex G-matrix interactions CEG07, from which nucleon-nucleus (NA) and nucleus-nucleus (AA) folding potentials are obtained. The CEG07 G-matrices are derived from the free-space nucleon-nucleon interaction, the Extended Soft Core (ESC) model, including the TBF contributions composed of the three-body repulsive (TBR) and attractive (TBA) components. Using CEG07, we have analyzed the elastic scattering of NA and AA systems. For NA systems, we have tested the optical potentials obtained by the single-folding procedure with CEG07 in the cases of the proton elastic scattering. We have further applied the CEG07 G-matrix to the AA systms in the framework of the double-folding model and analyzed the elastic scattering of complex nuclei systems at E/A = 70 ∼ 135 MeV. The TBF (especially TBR) effect is clearly seen in all cases investigated.

We compare results of dynamical modeling of the fission process with predictions of the Kramers formulas. For the case of large dissipation these are two: the integral rate R_I and its approximation R_O . As the ratio of the fission barrier height B_f to the temperature T, , reaches 4, any analytical rate is expected to agree with the dynamical quasistationary value R_D within 2%. We perform modeling using several potentials and find that the difference between the R_O and the R_D sometimes exceeds 20% even for > 4. Such discrepancy is not acceptable nowadays because it is comparable to the quantum, non-markovian and multidimensional effects. The features of the potentials which cause this disagreement are identified and studied. It is demonstrated that this is the R_I, not the R_O, which meets the expectation above irrespectively of the potential profile.

RIBRAS, Radioactive Ion beam in Brasil, is a system based on superconducting solenoids which can produce low energy RNB (Radioactive Nuclear Beams) at the University of São Paulo, Brazil. Secondary radioactive beams of light particles such as ⁶He, ⁷Be and ⁸Li have been produced and low energy elastic scattering and transfer reaction experiments have been performed. The recent scientific program using this facility includes elastic scattering and transfer reactions of ⁶He halo nucleus on ⁹Be, ²⁷Al, ⁵¹V and ¹²⁰Sn targets and ⁸Li on ⁹Be, ¹²C and ⁵¹V targets. The total reaction cross section as a function of energy has been extracted from the elastic scattering data and the role of breakup of weakly bound or exotic nuclei is discussed. Also spectroscopic factors have been obtained from the transfer reactions.

We obtain the nuclear proximity potential by using semiclassical extended Thomas Fermi (ETF) approach in Skyrme energy density formalism (SEDF), and use it in the extended ℓ-summed Wong formula under frozen density approximation. This method has the advantage of allowing the use of different Skyrme forces, giving different barriers. Thus, for a given reaction, we could choose a Skyrme force with proper barrier characteristics, not-requiring extra "barrier lowering" or "barrier narrowing" for a best fit to data. For the ⁶⁴Ni+¹⁰⁰Mo reaction, the ℓ-summed Wong formula, with effects of deformations and orientations of nuclei included, fits the fusion-evaporation cross section data exactly for the force GSkI, requiring additional barrier modifications for forces SIII and SV. However, the same for other similar reactions, like ^58,64Ni+^58,64Ni, fit the data best for SIII force. Hence, the barrier modification effects in ℓ-summed Wong expression depend on the choice of Skyrme force in semiclassical ETF method.

The synthesis of the new chemical element with atomic number Z=117 is presented. The isotopes ²⁹³117 and ²⁹⁴117were produced in fusion reactions between ⁴⁸Ca and ²⁴⁹Bk. The ²⁴⁹Bk was produced in the High Flux Isotope Reactor and chemically separated at Oak Ridge. Decay chains involving eleven new nuclei were identified by means of the Dubna Gas Filled Recoil Separator. The measured decay properties show a strong rise of stability for super-heavy nuclei toward N=184.

Fusion excitation functions and transfer probabilities were measured for ²⁸Si+^90,94Zr systems around the Coulomb barrier, using the recoil mass separator, Heavy Ion Reaction Analyzer (HIRA) at Inter University Accelerator Centre (IUAC), New Delhi. The aim of these experiments was the study of coupling effects of inelastic and transfer channels on the sub-barrier fusion cross section enhancement. The experimental fusion cross sections were found to be strongly enhanced as compared to one dimensional barrier penetration model (1-d BPM) predictions in both the cases. The trend of data could be easily reproduced theoretically using coupled channels code CCFULL in the case of ²⁸Si+⁹⁰Zr but the observed enhancement could not be explained in the case of ²⁸Si+⁹⁴Zr, which may be attributed to the coupling of multinucleon transfer channels as both isotopes have similar collective strengths. The transfer probabilities in the case of ⁹⁴Zr were found to be substantially higher than for ⁹⁰Zr in the sub-barrier region.

We present our recent calculations on fragmentation by varying the mass asymmetry of the colliding nuclei using the reactions of ₂₆Fe⁵⁶ +₄₄Ru⁹⁶ (η = 0.2), ₂₄Cr⁵⁰ + ₄₄Ru¹⁰² (η = 0.3), ₂₀Ca⁴⁰ +₅₀Sn¹¹² (η = 0.4), ₁₆S³² +₅₀Sn¹²⁰ (η = 0.5), ₁₄Si²⁸ +₅₄Xe¹²⁴ (η = 0.6), ₈O¹⁶ +₅₄ Xe¹³⁶ (η = 0.7) at a fixed center of mass energy E_c.m. = 250 MeV/nucleon. For the present study, total mass of the system is kept constant (A_TOT = 152). The measured distributions are given as a function of the total charge of all projectile fragments, Z_bound. The well known trend of rise and fall in the multiplicity of intermediate mass fragments for symmetric colliding nuclei is reproduced nicely. Such trends are, however missing for larger asymmetric reactions.

Modern nucleon-nucleon interaction models can be probed quantitatively in the three-nucleon environment by comparing predictions based on rigorous solutions of the Faddeev equations with the measured observables. Proper description of the experimental data can be achieved only if the dynamical models include subtle effects of suppressed degrees of freedom, effectively introduced by means of genuine three-nucleon forces. A large set of high precision, exclusive cross-section data for the ¹H(d,pp)n breakup reaction at 130 MeV, contributes significantly to constrain the physical assumptions underlying the theoretical interaction models. Comparison of nearly 1800 cross section data points with the predictions using nuclear interactions generated in various ways, allowed to establish for the first time a clear evidence of importance of the three-nucleon forces in the breakup process. Moreover, the results, supplemented by a set of cross sections from another dedicated experiment, confirmed predictions of sizable Coulomb force influences in this reaction.

The transverse flow of intermediate mass fragments (IMFs) has been investigated for the 35 MeV/u ⁷⁰Zn+⁷⁰Zn, ⁶⁴Zn+⁶⁴Zn, and ⁶⁴Ni+⁶⁴Ni systems. A transition from the IMF transverse flow strongly depending on the mass of the system, in the most violent collisions, to a dependence on the charge of the system, for the peripheral reactions, is shown. This transition was shown to be sensitive to the density dependence of the symmetry energy using the antisymmetrized molecular dynamics model. The results present a new observable, the IMF transverse flow, that can be used to probe the nuclear Equation of State. Comparison with the simulation demonstrated a preference for a stiff density dependence of the symmetry energy.

We carried out the experiment of the ¹H(d,pp)n reactions at E_d = 26 MeV at RCNP and that of the ²H(p, pp)n reactions at E_p = 13 MeV at KUTL. The data of the differential cross sections was measured and compared with the Faddeev calculations based on the various nucleon-nucleon (NN) interactions with/without the Coulomb interactions or the three-nucleon force (3NF). The data is overestimated by the theoretical predictions by less than 10 %. This result is very different from the data at E=9.5 MeV reported from Köln, which showed the large discrepancies between the data and the Faddeev calculations.

The reaction dynamics induced by the ¹⁷F Radioactive Ion Beam on the proton-shell closed ⁵⁸Ni target was studied at two colliding energies slightly above the Coulomb barrier. Charged reaction products were detected at forward angles and the quasi-elastic differential cross section was analyzed within the framework of the optical model in order to extract the reaction cross section and to investigate the relevance of direct reaction channels (inelastic scattering, breakup and transfer) at near-barrier energies. The comparison with the reaction induced by double-magic tightly-bound ¹⁶O projectiles on the same target showed that the ¹⁷F reaction cross section is moderately enhanced at the lower secondary beam energy. Direct reaction channels were also found to be more relevant than for the corresponding ¹⁶O-induced reaction.

A microscopic calculation of the optical potential for nucleon-nucleus scattering has been performed by explicitly coupling the elastic channel to all the particle-hole (p-h) excitation states in the target and to all relevant pickup channels. These p-h states may be regarded as doorway states through which the flux flows to more complicated configurations, and to long-lived compound nucleus resonances. We calculated the reaction cross sections for the nucleon induced reactions on the targets ^40,48Ca, ⁵⁸Ni, ⁹⁰Zr and ¹⁴⁴Sm using the QRPA description of target excitations, coupling to all inelastic open channels, and coupling to all transfer channels corresponding to the formation of a deuteron. The results of such calculations were compared to predictions of a well-established optical potential and with experimental data, reaching very good agreement. The inclusion of couplings to pickup channels was an important contribution to the absorption. For the first time, calculations of excitations account for all of the observed reaction cross-sections, at least for incident energies above 10 MeV.

The asymptotic time derivative of the total dipole signal is proposed as an useful observable to investigate on Isospin equilibration phenomenon in multi-fragmentation processes. The study has been developed to describe charge/mass equilibration processes involving the gas and liquid "phases" of the total system formed during the early stage of a collision. General properties of this observable and the links with others isospin dependent phenomena are discussed. In particular, the ⁴⁰Cl+²⁸Si system at 40 MeV/nucleon is investigated by means of semiclassical microscopic many-body calculations based on the CoMD-II model. The study of the dynamical many-body correlations produced by the model also shows how the proposed observable is rather sensitive to different parameterizations of the isospin dependent interaction.

The temperature of a compound nucleus should decrease for the higher values of its spin angular momentum and so the spectra of the heavier evaporation fragments emitted from the compound nucleus should have progressively steeper slopes. To test this idea, we formed the same compound nucleus ¹⁰⁵Ag at the same excitation energy (E_X=76 MeV) and with very similar spin distribution by ¹⁶O+⁸⁹Y and ¹²C+⁹³Nb reactions and studied back-angle alpha to carbon particle emissions. The compound nucleus character of the reaction was established from the angular distribution of the emitted fragments and the lack of any entrance channel dependence of the angle-integrated yields of the fragments. It was found that the temperatures of the ensembles of the residual nuclei as obtained from the slopes of alpha, lithium, boron, carbon spectra remain about 3 MeV in most cases and higher (about 4.2 MeV) for lithium emission, whereas the statistical model codes predict decrease of the corresponding temperatures from 3 MeV (for alpha) to 1.65 MeV (for carbon). The result could not be understood by adjusting the parameters of the statistical models and might imply the effect of the lifetime of the exit channel fragment plus residual dinuclear system.

In this work we describe a method to study scattering processes. The method, which is based on the Kohn Variational Principle, has been generalized to be applicable for calculating any partial wave phase shift and studying multichannel processes. It shows fast convergence when applied to three-body reactions described with the hyperspherical adiabatic method. The pattern of convergence is similar to the one found when the method is applied to obtain bound states.

The vector analyzing power has been measured for the elastic scattering of neutron-rich ⁶He and ⁸He from polarized protons at 71 MeV/A making use of a newly constructed solid polarized proton target operated in a low magnetic field of 0.1 T and at a relatively high temperature of 100 K. An optical model analysis revealed that the spin-orbit potentials for ⁶He and ⁸He are characterized by shallow and long-ranged shape compared with the global systematics of stable nuclei. Such a characteristics reflect a diffused density distribution of the neutron-rich isotopes.

Measurements of a complete set of deuteron analyzing powers (iT₁₁, T₂₀, T₂₁, and T₂₂) for elastic deuteron-proton scattering at 250 MeV/nucleon have been performed with polarized deuteron beams at RIKEN RI Beam Factory. The obtained data are compared with Faddeev calculations based on the modern nucleon–nucleon forces together with the Tucson- Melbourne'99 and UrbanaIX three-nucleon forces.

The prompt γ radiation originating from the dynamical dipole mode decay was investigated in the ¹⁹²Pb composite system employing the ⁴⁰Ca + ¹⁵²Sm and ⁴⁸Ca + ¹⁴⁴Sm reactions at E_lab=11 and 10.1 MeV/nucleon, respectively. The γ-ray energy spectra at various polar angles were obtained for fusion-evaporation and fission events by detecting the high energy γ rays with the MEDEA experimental apparatus in coincidence with evaporation residues and fission fragments. Preliminary results of this experiment show that the dynamical dipole mode survives in collisions involving heavier mass reaction partners than those studied previously. As a fast cooling mechanism on the fusion path, the prompt dipole γ radiation could be of interest for the synthesis of super-heavy elements through "hot" fusion reactions.

Possibilities of deducing the asymptotic normalisation constant C_b of the 2₁⁺ subthreshold bound state of ¹⁶O from the low-energy ¹²C+α d-wave scattering phase shifts are studied. Within the potential model, it is shown that such a connection exists in principle, either by studying the range of potentials fitting the phase shifts, or by using the effective range expansion. However, present-day data do not seem sufficient to strongly constrain C_b, as values ranging from 20 to 180 × 10³ fm^−1/2 are obtained, depending on the order of the chosen effective-range expansion.

A theory of partial fusion is used to calculate the competition between escape (breakup) and absorption (compound-nucleus production) following a deuteron-induced transfer of one neutron to a heavy nucleus at energies above the neutron escape threshold. Preliminary calculations are shown to yield excellent results for the competition between neutron absorption and neutron escape when deposited on actinides at energies up to 3 MeV.

The ASACUSA (the Atomic Spectroscopy And Collisions Using Slow Antiprotons) collaboration has developed various kinds of monitors which both destructively and non-destructively measure the spatial profiles of pulsed antiproton beams at the Antiproton Decelerator (AD) of CERN. These include detectors consisting of foil and wire electrodes based on gas ionization or secondary electron emission, which are compatible with ultra-high vacuum conditions. A new beam profile monitor with a grid of electrode pads fabricated on a normal glass-epoxy circuitboard was adapted for the measurement of antiproton annihilation cross sections. This monitor has an active area of 40 mm × 40 mm and a spatial resolution of 4 mm. It can measure the spatial profile of 40-50-ns-long beam pulses containing > 10⁴ antiprotons striking each anode strip.

Nuclear fragment yield data has been analyzed using the Landau free energy description to investigate the critical phenomena in the fragmentation of quasiprojectile in the reactions ^78,86Kr+^58,64Ni at beam energy of 35 MeV/nucleon. The data on mirror nuclei yield ratio for A=3 and 7 showed an exponential dependence on the isospin asymmetry of the quasiprojectile as predicted by the Landau free energy approach. The slope parameter, obtained from linear fit to the plots of the logarithm of mirror nuclei yield ratios as a function of isospin asymmetry of the fragmenting source provided a reasonable estimate of the nuclear symmetry energy, and showed a systematic decrease with increasing excitation energy of the quasiprojectile.

Results from the study of isospin asymmetric Sn+Sn collisions at E/A=35 MeV and 50 MeV, collected with the LASSA and the Chimera detectors at the NSCL of MSU, respectively, are shown. The diffusion of neutrons and protons between projectiles and targets with different N/Z-asymmetries is studied by means of imbalance ratios measurements. The obtained results and their comparison to transport model simulations provide constraints on the density dependence of the symmetry energy. The systematic study of these phenomena at different impact parameters also allows us to explore isospin transparency and stopping phenomena in more central collisions, with important implications about the attainment of chemical equilibrium in central collisions at 35 MeV/nucleon.