The Effect of Nuclear Rotation on the Collective Transport Coefficients

We have examined the influence of rotation on the potential energy and the transport coefficients of the collective motion (friction and mass coefficients). For axially symmetric deformation of nucleus Th-224 we have found that at excitations corresponding to temperatures T > 1 MeV the shell correction to the liquid drop energy practically does not depend on the angular rotation. The friction and mass coefficients obtained within the linear response theory for the same nucleus at temperatures larger than T=2 MeV are rather stable with respect to rotation provided that the contributions from spurious states arising due to the violation of rotation symmetry are removed. At smaller excitations both friction and mass parameters corresponding to the elongation mode are growing functions of rotational frequency.Comment: 16 pages, 5 eps figures, Latex, submitted to Nucl.Phys.

Recovering dynamic distortions on output of channel transmitted continuous signals

Встатті розглядаються алгоритми відновлення неперервних сигналів, на які динамічно впливають істотні спотворення у виглядів шумів. Показано, що розроблені алгоритми цифрової фільтрації можна застосувати для стабільної роботи оператора інверсії каналу. Для забезпечення стійкості розв’язку некоректних задач застосовуються методи регуляризації з максимальним використанням додаткової апріорної інформації про сигнал ішум. Приведено результати комп'ютерних експериментів.Signal restoring algorithms, subjected to essential dynamic distortions in channels transmitting continuous signals in conditions of noise availability are considered in this paper. It is shown, that the application of developed algorithms digital filtration made possible to avoid unstable operation of operator inversion of the channel. For maintenance stability of the delivered problem solution with the purpose of maximum use additional a priory information on required signal and noise regularization methods of ill posed problems are used. Some results of computer experiments are shown

Mean-field description of ground-state properties of drip-line nuclei. (I) Shell-correction method

A shell-correction method is applied to nuclei far from the beta stability line and its suitability to describe effects of the particle continuum is discussed. The sensitivity of predicted locations of one- and two-particle drip lines to details of the macroscopic-microscopic model is analyzed.Comment: 22 REVTeX pages, 13 uuencoded postscript figures available upon reques

Self-consistent quantal treatment of decay rates within the perturbed static path approximation

The framework of the Perturbed Static Path Approximation (PSPA) is used to calculate the partition function of a finite Fermi system from a Hamiltonian with a separable two body interaction. Therein, the collective degree of freedom is introduced in self-consistent fashion through a Hubbard-Stratonovich transformation. In this way all transport coefficients which dominate the decay of a meta-stable system are defined and calculated microscopically. Otherwise the same formalism is applied as in the Caldeira-Leggett model to deduce the decay rate from the free energy above the so called crossover temperature $T_0$.Comment: 17 pages, LaTex, no figures; final version, accepted for publication in PRE; e-mail: [email protected]

The deformation energy and fission barriers of heavy nuclei

The macroscopic part of the fission barriers of medium and heavy nuclei is calculated looking for the minimum of liquid drop energy at fixed volume and elongation without using any shape parameterization. The fission barrier heights, obtained within the Lublin-Strasbourg Drop model, are approximated by a simple analytical expression as functions of Z and (N – Z)/A only. In addition, using the topological theorem by Myers and Świa¸tecki which allows to represent the barrier height as the sum of the ground state microscopic correction (which is calculated and tabulated for all nuclei) and the liquid–drop fission barrier, we propose a simple but quite accurate approximation of the fission barrier heights

The description of the excitation energy sharing in nuclear fission within the Langevin approach

We apply the four-dimensional Langevin approach to the description of fission of 235U by neutrons and calculate the dependence of the excitation energy of fission fragments on their mass number. For this we run the Langevin equations until the compound nucleus splits into two separated fragments. This is possible since the we used in this work two-center shell model shape parametrization that describes well both compact and separated shapes. The excitation energies of each fragment are calculated assuming that the temperatures of both fragments are the same. The deformation energy of the fragment immediately after scission is added to its excitation energy. The saw-tooth structure of the dependence neutron multiplicity on the fragment’s mass number in reaction 235U + n at En = 5 Mev is qualitatively reproduced

The Scission Point Configuration and the Multiplicity of Prompt Neutrons

AbstractWe defined the optimal shape which fissioning nuclei attain just before the scission and calculated the deformation energy as function of the mass asymmetry and elongation at the scission point. The calculated deformation energy is used in quasi-static approximation for estimation of the mass distribution of fission fragments, total kinetic and excitation energy of fission fragments, and the total number of prompt neutrons. The calculated results reproduce rather well the experimental data on the position of the peaks in the mass distribution of fission fragments, the total kinetic and excitation energy of fission fragments. The calculated value of neutron multiplicitiy is somewhat larger than experimental results

Pre-scission Model Predictions of Fission Fragment Mass Distributions for Super-heavy Elements

The total deformation energy at the moment of the neck rupture for the heaviest nuclei for which SF has been detected (279–281Ds, 281Rg and 282–284Cn) is calculated using the Strutinsky’s prescription and nuclear shapes described in terms of Cassinian ovals (defined by an elongation parameter α=0.98) generalized by the inclusion of four additional shape parameters: α1, α3, α4, and α6. Supposing that the probability of each point in the deformation space is given by Boltzmann factor, the distribution of the fission-fragment masses is estimated. The octupole deformation α3 at scission is found to play a decisive role in determining the main feature of the mass distribution: symmetric or asymmetric