The mass and total kinetic energy distributions of the fission fragments in the fission of even-even isotopes of superheavy elements from Hs (Z=108) to Og (Z=118) are estimated using a pre-scission point model. We restrict to nuclei for which spontaneous fission has been experimentally observed. The potential energy surfaces are calculated with Strutinsky’s shell correction procedure. The parametrization of the nuclear shapes is based on Cassini ovals. For the just before scission configuration we fix a = 0.98 , what corresponds to rneck = 2 fm, and take into account another four deformation parameters: a1 , a1 , a4 , a6 . The fragment-mass distributions are estimated supposing they are due to thermal fluctuations in the mass asymmetry degree of freedom just before scission. The influence of the excitation energy of the fissioning system on these distributions is studied. The distributions of the total kinetic energy (TKE) of the fragments are also calculated (in the point-charge approximation). In Hs, Ds and Cn isotopes a transition from symmetric to asymmetric fission is predicted with increasing neutron number N (at N = 168). Super-symmetric fission ocurs at N = 160. When the excitation energy increases from 0 to 30 MeV, the peaks (one or two) of the mass distributions become only slightly wider. The first two moments of the TKE distributions are displayed as a function of the mass number A of the fissioning nucleus. A slow decrease of the average energy and a minimum of the width (at N =162) is found.
Theoretical description of the experimental data on the formation of various isotopes in reactions (3He+194Pt) and (3He+45Sc) requires taking into account neutron and proton transfer channels, as well as fusion-evaporation channels. To calculate the probabilities of nucleon transfer as well as transfer cross sections the time-dependent Schrodinger equation (TDSE) has been solved numerically. Fusionevaporation was taken into account using the statistical model code of the NRV web knowledge base. Results of calculations are in agreement with experimental data.
The NUSTAR Collaboration will perform experiments with relativistic exotic nuclei and superheavy elements at GSI and FAIR. Presently, several new FAIR detector systems are under construction for high-resolution spectrometer experiments, decay spectroscopy, reaction studies with internal and external targets, and for experiments with stopped and re-accelerated beams. Due to the delayed start of the FAIR project, the new FAIR detectors will be used at GSI with beams from the existing accelerators (UNILAC, SIS-18/ESR) and set the scene for new experimental avenues, not existing so far. The planned intermediate research program and the new opportunities are outlined.
We demonstrate that the unconventional electron-phonon interactions, charge inhomogeneity and charge ordering in underdoped cuprates play an important role in metal-insulator transitions and nanoscale phase separation. In so doing, we argue that charge carriers (i.e. hole polarons) in these systems segregate into insulating (carrier-poor) and metallic/superconducting (carrier-rich) regions as a result of their speciﬁc ordering. We show that the metal-insulator transitions, nanoscale phase separation and coexisting insulating and metallic/superconducting phases are manifested in the unusual temperature dependences of the magnetic susceptibility and resistivity and in the suppression of superconductivity in various underdoped cuprates.
Synthesis, X-ray phase analysis, electron microscopy and investigations of the thermoelectric and thermal properties of nanocrystalline copper sulﬁde alloys contained sodium are presented. At room temperature, the alloys are a mixture of three phases of copper sulﬁde - the monoclinic phase of Na2Cu4S3, the hexagonal phase of Cu2S and the cubic phase of Cu9S5 (digenite). The predominant phase is
Na2Cu4S3 (with content from 57 to 85 volume %). The particle sizes in the compacted samples lie in the range from 20 to 400 nm. For all samples DSC studies revealed a ﬁrst-order phase transition in the (370-380) K region with enthalpies from 5234 to 11720 J/kgK. The heat capacity varies within the range (0.15-0.48) J/(gK). The electrical conductivity, Seebeck coefﬁcient and thermal conductivity were measured in the temperature range from 290 to 590 K. A very low thermal conductivity of the samples was observed in the interval of (0.1-0.6) Wm−1K−1. The Seebeck coefﬁcient has a value higher than 0.2 mV/K for Na 0.15 Cu 1.85 S composition, but a low electrical conductivity about 10 S/cm limits the maximum dimensionless thermoelectric efﬁciency ZT of the material at 0.3 in the temperature range 290-590 K.
The isobaric-analog resonancesfor nuclei around the neutron shell closures at N = 20, 50, 82 are treated in the fully self-consistent Density Functional plus Continuum Quasiparticle Random Phase Approximation (DF+CQRPA).The aim is to check how the self-consistency is preserved in the calculations for long isotopic chains. The beta-decay half-lives and delayed multi-neutron emission branchingare calculated for the reference Ni isotopic chain. The relative contributions of the GT and first-forbidden transitions are compared with that of the relativistic QRPA and Finite Amplitude Method. The accuracy of the global beta decay calculations performed within FRDM+RPA, DF+CQRPA and RHB+QRPA models are
In this study the results of structural and morphological changes in Ni12+ heavy ion irradiated BeO ceramics are presented. Irradiation was carried out on DC-60 heavy ion accelerator using Ni12+ ions with an energy of 100 MeV with irradiation fluence of 1013 -1014 ions/cm2 . It has been determined that change in magnitude of atom displacements from lattice sites is exponential, which is conditioned by defect overlap regions occurrence at fluence of 1014 ions/cm2 , followed by formation of a large number of migrating defects in structure, leading to crystal structure distortion and deformation due to chemical bonds rupture. In case of defect overlap areas generation, characteristic for irradiation fluences of 5 × 1013 - 1014 ions/cm2 , amorphous inclusions formation of more than 5% was observed, that leads to thermal conductivity decrease by (15-20)%.
The article presents working results of radiation status survey in the territory adjacent to the “Atomic lake”, a venue of the ﬁrst USSR excavation explosion. In the course of research, a picture of areal radiation contamination has been obtained in the territory with technogenic radionuclides 137Cs, 241Am, 152Eu. A pattern of radionuclide distribution in depth is shown at different spots (crater bank, Shagan river ﬂoodplain, the area of the external reservoir). Data is presented on concentrations of technogenic radionuclides 3H, 239+240,238Pu, 90Sr, 60Co, 154Eu, 152Eu in soil.
The commissioning of the new fragment separator ACCULINNA-2 at FLNR JINR is accomplished. The separator is destined to expand the possibilities in studies of dripline nuclei performed with the exotic secondary radioactive ion beams (RIBs) at energies of (5 – 50) AMeV. The projected high transmission and purification level were confirmed experimentally for a number of RIBs in the last two years. The ACCULINNA-2 setup will become a backbone facility at FLNR for the research in the field of light exotic nuclei. This report shows the current status of the separator, describes the obtained RIBs parameters and first experiments as well, provides the overview of the developing detection, monitoring and control subsystems.
Eurasian journal of physics and functional materials