Deep Inelastic Heavy Ion Collisions Research Articles

Estimation of the spatial decoherence time in circular quantum dots

We propose a simple phenomenological model to estimate the spatial decoherence time in quantum dots. The dissipative phase-space dynamics is described in terms of the density matrix and the corresponding Wigner function, which are derived from a master equation with Lindblad operators linear in the canonical variables. The formalism was initially developed to describe diffusion and dissipation in deep inelastic heavy-ion collisions, but an application to quantum dots is also possible. It allows us to study the dependence of the decoherence rate on the dissipation strength, the temperature, and an external magnetic field, which is demonstrated in illustrative calculations on a circular GaAs one-electron quantum dot.

Development of shell closures at N=32, 34. II. Lowest yrast excitations in even-even Ti isotopes from deep-inelastic heavy-ion collisions

Development of shell closures at N=32, 34. II. Lowest yrast excitations in even-even Ti isotopes from deep-inelastic heavy-ion collisions

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.

Friction coefficient for deep-inelastic heavy-ion collisions

Based on the microscopic model, the friction coefficient for the relative motion of nuclei in deep-inelastic heavy-ion collisions is calculated. An advantage of the suggested method is that it allows one to consider the relative motion of nuclei and the intrinsic motion self-consistently. The radial dependence of the friction coefficient is studied and the results are compared with those found by other methods. It was demonstrated that the kinetic energy dissipation in deep-inelastic heavy-ion collisions is a gradual process which takes up a significant part of a reaction time. A decrease of the radial friction coefficient with a heating of nuclei is shown.

Multi-Neutron and Proton Transfer Reactions in Deep Inelastic Heavy-Ion Collisions

Multi-Neutron and Proton Transfer Reactions in Deep Inelastic Heavy-Ion Collisions

Gamma-ray studies of 119, 121, 123Sn isomers formed in deep inelastic heavy ion collisions

Yrast isomers in 119Sn, 121Sn and 123Sn have been identified among products of heavy ion collisions with 124Sn targets 10–15% above the Coloumb barrier. Isomeric decay schemes are reported, and further evidence for half-filling of the ν h 11 2 subshell at N = 73 is presented. For ( ν h 11 2 n seniority-3 states, observed level energies agree well with results of fractional parentage calculations.

Gamma-ray studies of 119, 121, 123Sn isomers formed in deep inelastic heavy ion collisions

Gamma-ray studies of 119, 121, 123Sn isomers formed in deep inelastic heavy ion collisions

Langevin description of heavy-ion collisions within the surface friction model

The surface friction model including deformation modes and thermal fluctuations is applied to fusion and deep-inelastic collisions of heavy ions. The Langevin model used in previous work is modified in several respects. The action of the fluctuating force leads to enhanced backscattering of trajectories after they have sormounted the barrier. This gives rise to the formulation of a new criterion for fusion, which leads to a universal description of low-energy heavy-ion scattering. We calculate fusion probabilities, total cross sections for the branching of fusion and deep-inelastic collisions, and fusion spin distributions. A comparison with experimental data for a variety of systems is carried out.

The microscopic treatment of proton and neutron multiple transfer in DIC

The proton and neutron transfer in deep-inelastic heavy-ion collisions (DIC) is investigated in the framework of the microscopical model. It is shown that the isospin dependence of the single-particle potential is important for the correct description of the experimental data. For illustration different characteristics of the reactions238U+40,48Ca,197Au+40Ar and100Mo+40Ar are calculated. The qualitative agreement of the theoretical results with experimental data is demonstrated. Model calculations indicate that theN/Z-equilibrium process is monotonic. The calculated isotope production cross sections of light elements are in agreement with the Qgg-systematics.

Are δ-Electrons an Atomic Clock for Deep-Inelastic Heavy-Ion Collisions?(New Trends in Nuclear Collective Dynamics)

Are δ-Electrons an Atomic Clock for Deep-Inelastic Heavy-Ion Collisions?(New Trends in Nuclear Collective Dynamics)

Heat partition in damped reactions.

The effect of driving force on the division of excitation energy between the asymmetric colliding partners in deep inelastic heavy-ion collisions is studied in the nucleon-exchange model. For this purpose an event-by-event analysis using Monte Carlo simulation technique is performed. It is seen that the fraction of the total excitation energy carried by the projectile-like fragment is sensitive to the mass drift. The model is also applied to analyze the correlation between fragment mass and excitation energy for a given total energy loss and significant correlation is found. The reactions induced by $^{56}\mathrm{Fe}$ at 9 MeV/nucleon and $^{74}\mathrm{Ge}$ at 8.5 MeV/nucleon on $^{165}\mathrm{Ho}$ are considered in our analysis and the calculated correlations are in good agreement with the results obtained from the kinematic coincidence experiments.

Role of statistical fluctuations in the emission of delta electrons from dissipative heavy-ion collisions.

Energy spectra of \ensuremath{\delta} electrons emitted in coincidence with deep-inelastic heavy-ion collisions are calculated within a Langevin Monte Carlo description using the surface-friction model. We investigate the effects that wipe out the originally expected oscillatory pattern of the spectra. Emphasis is placed on the role of statistical fluctuations in extracting interaction time distributions of deep-inelastic collisions from the measured \ensuremath{\delta}-electron spectra. The calculations are compared to data for U+Au at 8.65 MeV/nucleon.

Effect of trajectory fluctuations on nucleon drift and diffusion in deep inelastic heavy ion collisions.

The role of trajectory fluctuations on the first and second moments obtained in the mean trajectory approximation for the proton and neutron distributions of the projectile-like fragments produced in deep inelastic heavy ion collisions has been studied in the framework of stochastic transfer of single nucleons. At each instant of time the neutron and proton numbers of the colliding nuclei are considered to be given by dynamically evolving Gaussian distributions generating trajectory fluctuations. The first moments calculated in this method differ considerably from those obtained in the mean trajectory approximation for the systems with strong gradient in the driving force around the point of injection. The second moments, however, do not change appreciably for all the systems studied.

Semiclassical theory of direct and deep inelastic heavy ion collisions

A sufficiently simple approach is formulated for the quantitative description of direct and multi-step processes in heavy ion collisions with arbitrary (not only small) mass, energy, and angular momentum transfer. The simplification is achieved owing to the use of semiclassical description of the colliding particles relative motion. The semiclassical approximation is used for the three-dimensional (not partial) distorted waves with accounting of all caustic properties, and the channel coupling is simulated by the dissipative forces. The transition amplitude is reduced to the one-dimensional integral along the so-called “transition lines” where the inelastic process is localized. The comparison is done with the experimental data and with exact calculations of some direct reaction cross sections. Heavy-ion-induced multi-step (quasidirect) massive transfer processes with the fast light particle formation are analyzed.

Semiclassical theory of direct and deep inelastic heavy ion collisions: V. I. Zagrebaev. Chuvash State University, Cheboksary 428000, USSR

Semiclassical theory of direct and deep inelastic heavy ion collisions: V. I. Zagrebaev. Chuvash State University, Cheboksary 428000, USSR

Semiclassical theory of direct and deep inelastic heavy ion collisions: V. I. Zagrebaev. Chuvash State University, Cheboksary 428000, USSR

Semiclassical theory of direct and deep inelastic heavy ion collisions: V. I. Zagrebaev. Chuvash State University, Cheboksary 428000, USSR

The treatment of heavy-ion collisions by Langevin equations

Fusion and deep-inelastic heavy-ion collisions are treated by Langevin equations within the framework of the surface friction model. Cross sections are calculated by Monte Carlo sampling of trajectories. An important result is that in contrast to what is usually assumed statistical fluctuations play a significant role in analysing heavy ion fusion data. It is demonstrated that in the analysis of deep-inelastic collisions the Langevin-Monte-Carlo method is more accurate than solving the corresponding Fokker-Planck equation by the usual moment expansion with the assumption of a gaussian distribution function.

Open quantum system of two coupled harmonic oscillators for application in deep inelastic heavy ion collisions

On the basis of the theory of Lindblad (1976) for open quantum systems the author derives master equations for a system consisting of two harmonic oscillators. The time dependence of expectation values, Wigner function and Weyl operator are obtained and discussed. The chosen system can be applied for the description of the charge and mass asymmetry degrees of freedom in deep inelastic collisions in nuclear physics.

Frictional forces for deep inelastic heavy ion collisions of deformed nuclei and application to 238U on 238U

For the description of deep inelastic reactions between deformed nuclei we present a classical model with frictional forces. The frictional forces and moments are derived from an extended double-folding model of Tsang and have a finite range. The frictional forces dissipate energy and angular momentum. In order to show the symmetries of the frictional forces and to simplify dynamical calculations we develop a multipole expansion of the frictional forces and moments. The model is applied to the deep inelastic reaction of 238U on 238U at E lab = 7.42 MeV/amu. By averaging over the initial orientations of the intrinsic symmetry axes of the deformed nuclei, we calculate the double-differential cross section d 2σ dE dθ cm , the differential one dσ dΩ , and th total one for the deep inelastic collision.

Constrained-phase-space approach to spin alignment in deep-inelastic heavy-ion collisions

A constrained-phase-space description of equilibrium in the angular momentum degrees of freedom is used to calculate the spin alignment in deep-inelastic heavy-ion reactions. The phase space is constructed by considering the internal degrees of freedom of the excited fragments and the conservation of angular momentum; the constraint which reflects the reaction dynamics is derived from the classical sticking condition. For several cases of mass-asymmetric heavy-ion reactions, the measured alignments are quantitatively reproduced. It is found that the alignment depends most sensitively on the initial angular momentum and on the fragment deformation at separation so that alignment data are useful to determine these quantities. Angular correlations of sequential-fission fragments from deep-inelastic reactions are also calculated. In the considered example, the measured in-plane anisotropy is explained as mainly resulting from the restrictions, imposed by the experimental setup, on the orientations of the orbital angular momenta in the entrance and exit channels.