Dynamical deformation of nuclei participating in deep-inelastic collisions

TheN/Z equilibration process taking place in deep-inelastic heavy ion collisions above the Coulomb barrier was studied by means of thick target gamma spectroscopy method. The analysis of gamma coincidence data obtained for four heavy ion systems gave complete distributions of primary reaction products which allowed to extract the most probableN/Z ratios as a function of mass. The comparison of experimentalN/Z values with expectations based on potential energy minimization leads to conclusion that during the crucial interaction time the involved nuclei are dynamically deformed.     

Incomplete deep-inelastic heavy-ion collisions

A phenomenological two-step reaction model is proposed, in which a direct projectile fragmentation in the initial stage is succeeded by a binary dissipative interaction between the heavy projectile fragment and the target in the final state. Multi-differential cross sections are estimated by folding the fragmentation cross section given in the local plane-wave Born approximation with the cross section for deep-inelastic collisions calculated within the classical friction model, including statistical fluctuations and mass transfer. For forward angles satisfactory results are obtained in comparison with the experimental data on inclusive spectra, angular distributions, angular correlations, γ-multipliciites, and element distributions in ²⁰Ne-induced reactions for bombarding energies of 10–20 MeV/nucleon.     

Interplay between particle-hole excitation and nucleon transfer in deep-inelastic collisions

The interplay between particle-hole excitation and nucleon transfer in deep-inelastic collisions is studied within an independent-particle model in which the relative motion is treated classically. The energy and angular momentum loss are evaluated selfconsistently in the model. The results show that the inclusion of the ph excitation strongly affects the transfer mode giving rise to a drift of the charge centroid towards charge asymmetry. The model predicts a roughly equal excitation energy for the two fragments rather than one proportional to their masses.     

A TI-59 model for nuclear reactions between complex nuclei

The role of the fluctuating part of the reaction amplitude in the angular distribution and in the energy dependence of the backangle cross section is investigated.     

Reactions between complex nuclei. The frontier between complete fusion and other dissipative collisions

In a first part, we discuss the distinction between complete fusion followed by the compound nucleus decay and incomplete fusion due to massive transfers. In the second part, we analyse the origin of fission-like products resulting from the disruption of a long-life intermediate system. Forl-waves corresponding to a rotating liquid drop fission barrier equal to zero, a quasi fusion process occurs which leads finally to characteristics very similar.     

High energy collisions between heavy nuclei

Neglecting Coulomb effects we derive a very simple analytical result for nucleus-nucleus elastic scattering in an optical limit of the Glauber approximation which has the property that it does not diverge at large momentum transfers when the center-of-mass correlation function is retained and is more accurate and easier to apply than the commonly used expressions which involve numerical integrations. We then derive a corresponding analytical expression for the elastic scattering amplitude which includes the Coulomb effects arising from point charge incident and target nuclei.     

A Langevin description of the competition between fusion and deep-inelastic collisions close to the barrier

A Langevin Monte Carlo method based on the surface friction model is used to investigate the competition between fusion and deep-inelastic collisions close to the barrier. Data for the⁵⁸Ni+^112,124Sn systems are analyzed. The measured excitation functions for fusion are well reproduced, whereas the calculated deep-inelastic cross sections deviate somewhat from experiment. Predictions for the corresponding spin distributions are made. Contrary to what is usually assumed they are not well separated in 1-space.     

Self-similar properties of collisions between light nuclei

A new way of representing data on the fragmentation of nuclei is suggested. The self-similar behavior of these processes, that is dictated by their kinematics, is demonstrated. The convenience of working in accelerated nuclei is emphasized, particularly for the determination of the binding energy of a wide class of nuclear fragments.     

A ParametrizedS-matrix model of deep-inelastic scattering

Deep-inelastic collisions are studied within a phenomenological approach based on a parametrized S matrix. The importance of a correct treatment of the Poisson sum is emphasized and the possibility of non-zero angular-momentum transfer is included. Statistical fluctuations are also considered. It is shown that the spin polarization is extremely sensitive to the treatment of the Poisson sum and that the spin alignment is independent of the scattering angle in the absence of statistical fluctuations.     

Pseudorapidity configurations in collisions between gold nuclei and track-emulsion nuclei

A method of parametrically invariant quantities is developed for studying pseudorapidity configurations in nucleus-nucleus collisions involving a large number of secondary particles. In simple models where the spectrum of pseudorapidities depends on three parameters, the shape of the spectrum may differ strongly from the shape of pseudorapidity configurations in individual events. Pseudorapidity configurations in collisions between gold nuclei of energy 10.6 GeV per nucleon and track-emulsion nuclei are contrasted against those in random stars calculated theoretically. An investigation of pseudorapidity configurations in individual events is an efficient method for verifying theoretical models.     

Spin transfer in deep-inelastic collisions of light ions

The angular correlations of α-particles emitted from the fragments of the reactions ¹⁶O + ¹⁶O, ³²S + ¹⁶O, ³²S + ¹⁶Al were determined in experiments that employed large-area, position-sensitive ionization chambers. The in-plane correlations are isotropic in the rest frame of the emitter, but the out-of-plane correlations have an anisotropy of approximately 3. From the anisotropies the spin projections √〈I_z²〉 onto the z-axis perpendicular to the reaction plane were determined. It is shown that the values of the spin projection can be qualitatively understood by the fractionation of the initial angular momentum under the requirement of energy, angular-momentum and particle-flux conservation.     

Hard-to-reach nuclei studied with deep-inelastic heavy-ion reactions

Spectroscopic studies performed with deep-inelastic heavy-ion reactions are reviewed for two regions of neutron-rich nuclei. The identification of isomers in nearly complete series of Sn isotopes and the resulting systematic of B(E2) values for isomeric transitions is presented and followed by the discussion of shell model states studied in neutron-rich Te isotopes including the new four neutron-hole isomers identified in ¹³⁰Te. Yrast spectroscopy studies of nuclei from the doubly magic ²⁰⁸Pb region are described by outlining the highest spin states observed in the ²⁰⁸Pb core nucleus. The E3 transitions observed abundantly in yrast decays are discussed within the framework of particle-octupole vibration coupling and the validity of a simple rule connecting energy shifts of octupole states built on one-particle states with the ones observed for two-particle states is demonstrated.Received: 15 January 2003, Published online: 23 March 2004PACS: 21.60.Cs Shell model - 23.20.Lv transitions and level energies - 27.60. + j - 27.80. + w      

A phenomenological woods-saxon potential for p-shell nuclei

The parameters of a Woods-Saxon potential well have been determined for ten p-shell nuclei by fitting the electron scattering form factors and single-particle binding energies. The resulting radius shows, for all but very light nuclei, a regular $\text{A}\text{1}\text{3}$ dependence while the depth smoothly decreases with the increasing proton energy. The observed energy dependence may be ascribed to the non-locality of the HF potential. An energy-independent non-local potential, compatible with elastic electron and proton scattering, is proposed in the energy range ?50 to +50 MeV.     

Hadron final states in deep-inelastic leptoproduction on nuclei

We discuss some aspects of the formation of inclusive hadron final states in deep-inelastic electro-, muo- and neutrinoproduction on nuclear targets.The inclusive final states are known to possess a remarkable Q² independence in interactions with free nucleons. Nevertheless, we prove that the nuclear spectra and mean multiplicities should have a rather specific and appreciable dependence on Q². In leptoproduction on heavy nuclei the yields of particles in nucleus fragmentation rise by a factor of two, as at the fixed energy transfer v one passes from incoherent scattering to diffraction scattering, and the total multiplicities change by 20–40%. The effects predicted seem to be detectable with the current and the near-future experimental facilities. Fermilab bubble chamber neutrino experiments and the coming SPS muon and neutrino experiments deserve special attention in this respect. We also comment on the possibilities offered by leptoproduction on nuclei for testing some absorption models.     

Mesonic processes in deep-inelastic electron scattering from nuclei

Inelastic electron scattering is considered in the energy and momentum transfer region associated with the quasielastic and 3-3 resonance pion electroproduction peaks. Calculations of two-nucleon ejection via two-body meson-exchange currents (MEC) and of pion electroproduction from threshold through the 3-3 resonance are presented using the Fermi gas model of the nucleus. The MEC contribution is found to be significant in this region, and helps to account for the discrepancy between theory and experiment in the “dip” between the quasielastic and 3-3 resonance peaks.     

Periodic multi-proton transfer strength in collisions between heavy nuclei

A periodic variation of the multi-proton transfer probability as a function of the nuclear charges of the residual nuclei has been observed in collisions of ²³⁸U with ¹¹⁰Pd and ¹²⁴Sn at bombarding energies close to the Coulomb barrier. After the N = 82 closed neutron shell of the light reaction partner is filled through multi-neutron transfer and an energy dissipation of about 100 MeV, transfer of pairs of protons is observed with modulated transfer strength. The proton multi-pair transfer dissipates no further energy.     

On a microscopic mechanism of collisions between extremely light nuclei

The method previously proposed by one of the present authors for studying three-body problems is generalized with the aim of exploring more complicated nuclear processes. The idea underlying the method consists in preserving the unitarity property for the scattering amplitude determined approximately. A specific analysis is performed for elastic collisions of ³He nuclei and for quasielastic deuteron-triton collisions. The theoretical results obtained by our method are compared with experimental data, and the agreement is found to be quite satisfactory.     

A phenomenological approch to α-clustering in heavy nuclei

We suggest that α-clustering may play an important role in the structure of heavy nuclei and propose a phenomenological model for treating it. We discuss the structure of spectra in two simple limits of this model.     

Gamma-ray spectroscopy of the neutron-rich Ni region through heavy-ion deep-inelastic collisions

Nuclei in the neutron-rich Ni region have been studied by γ-ray spectroscopy. Gamma-rays emitted from isomers, with T _1/2 > 1 ns, produced in heavy-ion deep-inelastic collisions were measured with an isomer-scope. The nuclear structure of the doubly magic ⁶⁸Ni and its neighbor ^69,71Cu is discussed on the basis of the shell model. Future experiments for more neutron-rich Ni nuclei are also viewed. Received: 1 May 2001 / Accepted: 4 December 2001