Nuclear physics began with the discovery of radioactivity. Several different forms of nuclear disintegration have been identified very early, starting with the familiar alpha, beta, and gamma decays. ...In 1938, nuclear fission joined the elite club of nuclear decays. The exotic, short lived nuclei, accessible experimentally during the last decades, have demonstrated quite a bit of skill and ingenuity in releasing its binding energy by spitting various particles out. This review is devoted to the traditional and unusual forms of nuclear radioactivity observed at the limits of nuclear stability.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UM
The H7 system was populated in the H2(He8,He3)H7 reaction with a 26 AMeV He8 beam. The H7 missing mass energy spectrum, the H3 energy and angular distributions in the H7 decay frame were ...reconstructed. The H7 missing mass spectrum shows a peak, which can be interpreted either as unresolved 5/2+ and 3/2+ doublet or one of these states at 6.5(5) MeV. The data also provide indications of the 1/2+ ground state of H7 located at 1.8(5) MeV with quite a low population cross section of ∼25 μb/sr within angular range θc.m.≃(17°-27°).
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
The most remote isotope from the proton dripline (by 4 atomic mass units) has been observed: K-31. It is unbound with respect to three-proton (3p) emission, and its decays have been detected in ...flight by measuring the trajectories of all decay products using microstrip detectors. The 3p emission processes have been studied by the means of angular correlations of S-28 + 3p and the respective decay vertices. The energies of the previously unknown ground and excited states of K-31 have been determined. This provides its 3p separation energy value S-3p of -4.6(2) MeV. Upper half-life limits of 10 ps of the observed K-31 states have been derived from distributions of the measured decay vertices.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
The method of asymptotic normalization coefficients is a standard approach for studies of two-body non-resonant radiative capture processes in nuclear astrophysics. This method suggests a fully ...analytical description of the radiative capture cross section in the low-energy region of the astrophysical interest. We demonstrate how this method can be generalized to the case of three-body 2p radiative captures. It was found that an essential feature of this process is the highly correlated nature of the capture. This reflects the complexity of three-body Coulomb continuum problem. Radiative capture 15O+p+p→17Ne+γ is considered as an illustration.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The study of radioactive ion beams (RIBs) is currently the main direction in the development of low-energy nuclear physics. In this work, consideration is given to the concept and the research agenda ...of the promising accelerator–storage ring complex for RIB research, which is a proposed international megaproject on the basis of the Flerov Laboratory of Nuclear Reactions (FLNR), JINR 1. The motivation of the new project is described and the RIB production characteristics of the complex are briefly presented, which are comparable in some aspects with the characteristics of advanced world centers known as RIB factories. In this project, emphasis is placed on investigating short-lived RIBs in storage rings. One unique feature of the project is the possibility of studying the interaction between electrons and radioactive isotopes in a collider experiment for determining fundamental properties of nuclear matter such as electromagnetic form factors of exotic nuclei.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Possible strategies of the development of low-energy nuclear physics in Russian Federation on the basis of the DERICA (Dubna Electron–Rare Isotope Collider fAcility ) project is examined. DERICA is a ...multiuser multipurpose facility for the production and study of radioactive isotopes (RI). In the research program of DERICA, emphasis is placed on studying RI in collector rings, but a stage-by-stage implementation of the program of DERICA would make it possible to address a wide range of fundamental problems at each stage of its development at the cutting-edge level. The ambitious goal of creating an
electron–radioactive ion
collider for studying basic properties of RI in electron–ion scattering is proposed for the final stage of development of DERICA.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Mechanism of simultaneous non-sequential four-neutron (4
n
) emission (or “true” 4
n
-decay) has been considered in phenomenological five-body approach. This approach is analogous to the model of the ...direct decay to the continuum often applied to 2
n
- and 2
p
-decays. It is demonstrated that 4
n
-decay fragments should have specific energy and angular correlations reflecting strong spatial correlations of “valence” nucleons orbiting in their 4
n
-precursors. Due to the Pauli exclusion principle, the valence neutrons are pushed to the symmetry-allowed configurations in the 4
n
-precursor structure, which causes a “Pauli focusing” effect. Prospects of the observation of the Pauli focusing have been considered for the 4
n
-precursors
7
H and
28
O. Fingerprints of their nuclear structure or/and decay dynamics are predicted.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
We perform mathematical modeling of the shape of dental arches. It is assumed that dental arches can be modeled by second-order curves. As a result of the analysis of the data of measurements ...performed for the diagnostic models of dentures, we compute both the coefficients of the quadratic form of the indicated second-order curves and the invariant of this form. Since the invariant of the second-order curve appears to be greater than zero, we make conclusion that the shapes of dental arches are described by the equation of ellipse. The parameters of the canonical equation of ellipse used to model the shape of dental arches are determined. We also develop a procedure for specifying the parameters of the model with an aim to use them in the processes of orthopedic and orthodontic treatments.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The soft dipole E1 strength function is calculated for the transition from the He60+ ground state to the 1- continuum He4+n+n. The calculations were performed within the hyperspherical harmonics ...formalism. The sensitivity of the results to the He6 ground-state structure and to final-state interactions, are analyzed. The large-basis calculations show the reliably converged results for soft dipole strength function and for momentum correlations of the He6→He4+n+n dissociation products. Transition mechanisms are analyzed based on the momentum correlations. The comparison with experimental data is provided.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UM
The reasons for fracture of fasteners made of 30KhGSA steel were analyzed. It was found that, in the case of fracture of bolts in the package connecting the frame elements, the damage of the bolts is ...the result of the fretting corrosion due to the mutual friction between bolts and elements of skin, belt, and tape. Fretting corrosion develops in the locations of the cadmium coating damage of bolts in the process of friction. The break-in scuffing of the openings and corrosive damage (fretting corrosion) triggering intergranular fracture, which is the most severe in the skin and tape, contribute to the fractures in the belt, skin, and tape. The reason for fracture is structural and technological factors: high stresses in the investigated package, micro-displacement of the mating parts, violation of the cadmium coating, insufficient protection against corrosion and environmental impact. Fracture of the self-locking nuts made of 30KhGSA steel with the anticorrosion cadmium coating used during assembly of an auxiliary gas turbine engine is induced by their severe overheating—the impact of the melted coating on the surface of the loaded nuts and penetration of the liquid metal into the base material along the grain boundaries. Application of the cadmium coating for the operation of the steel parts at a temperature exceeding (even for a short time) the melting temperature of Cd (
T
melt
= 320.9°C) under the condition of contact with the stressed metal owing to the Rebinder effect leads to a dramatic loss of strength and premature failure of the part. Fracture of the galvanized bolts made of 30KhGSA steel was studied in the process of the repeated static testing. It was found that several factors contributed to the onset of the multiple fractures: rough scratch marks, sandblasting performed before galvanizing with the use of large sand fractions, dents which contribute to the premature origin of cracks, areas with deposits formed during coating with loose adhesion of the layer. The presence of a large number of pits along with the fatigue grooves indicates the operation of the material under high load. The investigation was carried out by the method of optical and scanning electron microscopy applying the X-ray microanalysis.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
PDF
