Spectroscopic strengths for 6Li-induced alpha-particle transfers on 24Mg

²⁴Mg(⁶Li, d) angular distributions for transitions to low-lying states in ²⁸Si are well fitted by exact finite-range DWBA calculations and yield relative spectroscopic strengths in good agreement with theoretical predictions as well as with the corresponding results from other α-particle transfer reactions.     

The 6Li-induced three-nucleon transfer reaction on 40Ca

Analog (fp)³ states preferentially excited in the ${}^{40}\text{Ca}\text{(}{}^6\text{Li,t}\text{)}{}^{43}\text{Ti}$ and the ${}^{40}\text{Ca}\text{(}{}^6\text{Li}\text{, τ)}{}^{43}\text{Sc}$ reactions have been identified in the mass 43 mirror nuclei. A simple zero-range DWBA calculation made with a cluster form factor gives good agreement with the measured angular distributions, but spectroscopic strengths deduced for mirror levels do not agree. The 3p-0h states are excited with a rather uniform cross section not strongly correlated with spins.     

Progress in all-order breakup reaction theories

Progress in breakup reaction theories, like the distorted wave Born approximation, the continuum discretized coupled channels method and the dynamical eikonal approximation, is brought into focus. The need to calculate exclusive reaction observables and the utility of benchmark tests as arbitrators of theoretical models are discussed.     

Classical simulations of heavy-ion fusion reactions and weakly-bound projectile breakup reactions

Heavy-ion collision simulations in various classical models are discussed. Heavy-ion reactions with spherical and deformed nuclei are simulated in a classical rigid-body dynamics (CRBD) model which takes into account the reorientation of the deformed projectile. It is found that the barrier parameters not only on the initial orientations of the deformed nucleus, but also on the collision energy and the moment of inertia of the deformed nucleus. Maximum reorientation effect occurs at near- and below-barrier energies for light deformed nuclei. Calculated fusion cross-sections for ²⁴Mg + ²⁰⁸Pb reaction are compared with a static-barrier-penetration model (SBPM) calculation to see the effect of reorientation. Heavy-ion reactions are also simulated in a 3-stage classical molecular dynamics (3S-CMD) model in which the rigid-body constraints are relaxed when the two nuclei are close to the barrier thus, taking into account all the rotational and vibrational degrees of freedom in the same calculation. This model is extended to simulate heavy-ion reactions such as⁶Li + ²⁰⁹Bi involving the weakly-bound projectile considered as a weakly-bound cluster of deuteron and ⁴He nuclei, thus, simulating a 3-body system in 3S-CMD model. All the essential features of breakup reactions, such as complete fusion, incomplete fusion, no-capture breakup and scattering are demonstrated.     

A possible approach to breakup in nuclear reaction calculations

It is proposed to use the multi-channel Kato identity for estimating breakup amplitudes when an approximate scattering wave function is known from a variational calculation. Lines of connection are drawn with more familiar expressions for the breakup amplitudes.     

Review of quasi-elastic charge-exchange data in the nucleon-deuteron breakup reaction

The available data on the forward charge exchange of nucleons on the deuteron up to 2 GeV/nucleon are reviewed. The value of the inclusive nd → pnn/np → pn cross section ratio is sensitive to the fraction of spin-independent neutron-proton backward scattering. The measurements of the polarisation transfer in d(n, p){nn} or the deuteron analysing power in p{d, {pp})n in high-resolution experiments, where the final nn or pp pair emerge at low excitation energy, depend upon the longitudinal and transverse spin-spin up amplitudes. The relation between these types of experiments is discussed and the results compared with predictions of the impulse approximation model in order to see what new constraints they can bring to the neutron-proton database.     

Cross sections for the n+d breakup reaction

The n+d breakup cross section has been measured between 8 and 22 MeV by integrating the energy distributions of breakup protons and recoil deuterons observed in a deuterated scintillator. The results obtained deviate from the trend suggested by recent measurements of the cross section for proton-induced breakup and favour predictions based on a local N-N potential having a hard core in the singlet state.     

Neutron-deuteron breakup reaction as a tool for studying neutron-neutron interactions

An analysis of the most recent data on the reaction nd → pnn revealed a serious discrepancy between theoretical predictions and cross sections measured for this reaction in various configurations where the role of neutron-neutron interactions is important. In view of this, it seems necessary both to develop theoretical approaches and to obtain new experimental data. For this purpose, a setup for studying the neutron-deuteron breakup reaction was created at the Institute for Nuclear Research on the basis of the neutron beam in the RADEX channel and deuterium targets. This facility makes it possible to perform experiments over a broad region of primary-neutron energies (10–60 MeV) and in various (final-state interaction, quasifree scattering, and spatial-star) configurations. Preliminary results of the respective experiment were obtained for configurations of final-state neutron-neutron interaction and quasifree neutron-neutron scattering.     

A new formalism of inclusive breakup reactions and validity of the surface approximation

Austern and Vincent's formalism for the inclusive breakup reactions in DWBA is rewritten in a form in which the elastic and inelastic breakup processes are well discernible. This form is calculable exactly and hence we test the validity of the surface approximation used by Baur et al.     

Projectile like fragment production in Ar induced reactions around the Fermi energy

The production of projectile-like fragments (PLF) has been studied in Ar induced reactions on various targets. It shows very clearly, that besides the predominance of fragmentation for most of the products, the transfer process is still a very strong component for products nearby the projectile. The influence of the target neutron excess on the PLF production is investigated as well as the evolution with incident energy of the characteristics of the different competing processes.     

Application of dipole sum rules to transfer reaction strengths

Equations illustrating the application of dipole sum rules by relating the reaction strengths from single-particle transfer (stripping as well as pick up reactions) to the magnetic dipole moment of the target state (derived earlier) have been rewritten in a more symmetrical and user friendly form. The purpose of the present work is not to calculate the magnetic moment but to provide six different ways --from stripping and pick up reactions as well as from their combination, to study the discrepancies in the measurement of reaction strengths through their relationships with the magnetic moment. Received: 9 November 2000 / Accepted: 16 March 2001     

Analysis of orbital occupancy of valence neutron in 15C through Coulomb breakup reactions

Physics of Atomic Nuclei - The Coulomb breakup reactions 208Pb(15C, 14C + n)208Pb and 181Ta(15C, 14C + n)181Ta have been studied at 68 and 85 A MeV beam energies, respectively, within the framework...     

Measurement of the neutron-induced deuteron breakup reaction cross-section between 5 and 25 MeV

High-spin states in ¹⁸⁷Pt have been studied by means of ??-ray spectroscopy techniques. Known bands have been significantly extended and new bands have been found. The band structures are discussed in the framework of the cranking model and negative-parity states are compared with calculations performed with a semi-microscopic axial-rotor plus one-quasiparticle coupling model. Shape coexistence is observed from low excitation energy.     

Charged pion production and projectile breakup cIN 85A MeV 12C-induced heavy-ion reactions

Charged pions have been measured at 70° in coincidence with projectile-like fragments in ¹²C + ¹²C, ¹²C + ¹¹⁶Sn and ¹²C + ¹²⁴Sn reactions at 85A MeV. Neither the π⁺ emission nor the π⁻/π⁺ ratio exhibit differences for ¹²⁴Sn and ¹¹⁶Sn targets outside those expected from the isospin difference. Inconsistencies in the target mass dependence of the pion yield disappear if a correction for reabsorption is included. After this correction, we observe a strong, ~ A^1.1, mass dependence. The projectile breakup is significantly stronger for pion-producing collisions than for the average collision indicating a much stronger abundance of central collisions.     

Projectile breakup dynamics for 6Li + 59Co : Kinematical analysis of \alpha - d coincidences

A study of the kinematics of the $ \alpha$ -d coincidences in the ⁶Li + ⁵⁹Co system at a bombarding energy of E _lab = 29.6 MeV is presented. With exclusive measurements performed over different angular intervals it is possible to identify the respective contributions of the sequential and direct projectile breakup components. The angular distributions of both breakup components are fairly well described by the Continuum-Discretized Coupled-Channels framework (CDCC). Furthermore, a careful analysis of these processes using a semiclassical approach provides information on both their lifetime and their distance of occurrence with respect to the target. Breakup to the low-lying (near-threshold) continuum is delayed, and happens at large internuclear distances. This suggests that the influence of the projectile breakup on the complete fusion process can be related essentially to the direct breakup to the ⁶Li high-lying continuum spectrum.     

GEANT4 simulation of dp non-mesonic breakup reaction at 300 and 500 MeV

GEANT4 simulations of the reaction dp → ppn, i.e. the dp non-mesonic breakup reaction, at 300 and 500 MeV of deuteron energy for different detector configurations are presented. Two threads made from polyethylene and carbon with the thickness of 10 μm are used as targets. The goal of the simulations is to find a method by means of which the signal from the dp non-mesonic breakup can be separated from the background that mainly comes from the carbon content of the CH₂ target. The obtained results will be used in the experimental spin program that will be realized in Nuclotron in Dubna. The aim of this experimental investigation is to contribute to the elucidation of the structure of the spin dependent parts of the nucleon-nucleon and three-nucleon forces acting in the dp non-mesonic breakup. The deuteron energies will be ranging from 300 up to 500 MeV.