Kadmensky Stanislav Georgievich

Voronezh State University | vsu · Faculty of Physics

A theoretical description of the nature of the spin distribution (CP) of fragments of low-energy induced and spontaneous double fission of nuclei is carried out. For two deformed fission prefragments, a mechanism for pumping large values of their relative orbital momenta L and spins J, due to the combined influence of bending and wriggling vibratio...

A comparison is made of two theoretical approaches to describing the coefficients of T-odd asymmetries in the angular distributions of prompt γ-quanta and neutrons evaporated from thermalized fragments of the binary fission of non-oriented target nuclei by cold polarized neutrons, and in angular distributions of pre-scission α particles emitted in...

In employing the concept of the isotropy of space, the coefficients D of P-even, T-odd asymmetry in the angular distributions of prescission alpha particles emitted as third particles in the ternary fission of nonoriented target nuclei that is induced by polarized cold neutrons are expressed in the lowest orders of perturbation theory in the neutro...

for nuclear reactions that are two-body ones in the initial and final channels and which involve polarized particles, the T-null theorem stating the absence of vanishing observables in such reactions was proven in a number of studies by means of concepts of reaction \({\cal T}\) matrices that take into account general conservation laws along with T...

A detailed analysis of T-odd asymmetries in the reactions of true ternary fission of nuclei that involves the emission of prescission alpha particles is performed within quantum-mechanical fission theory. This analysis is based on taking into account the effect of quantum rotation of a fissile compound nucleus formed upon the capture of a polarized...

The approach proposed by A.B. Migdal for describing the virtual singlet diproton state is used to show the effect diproton decay channel has on the width and the angular distribution of emitted protons in the two-proton decay of a parent ⁴⁵Fe nucleus is negligible. A conclusion is reached on the leading role of the two-stage virtual mechanism of th...

Results are presented from investigating deviations of the coefficients of P-odd asymmetries in the angular distributions of fragments produced by the low-energy fissioning of actinide nuclei by polarized neutrons, calculated using the quantum fission theory with allowance for wriggling vibrations, from the coefficients of these asymmetries describ...

The possibility is investigated of observing deviations in the angular distributions of fragments from the low-energy binary fission of aligned actinide nuclei by resonant neutrons, calculated within the theory of quantum fission with allowance for the wriggling vibrations of fissile nuclei using angular distributions determined with Bohr’s formula...

The two-stage two-proton virtual nuclear decay theory and superfluid atomic nucleus model are used to investigate the total and partial widths, and the angular distributions of the emitted protons, for the two-proton diagonal virtual decay of the ground state of the \({}^{{19}}{\text{Mg}}\) nucleus into the ground state of the ¹⁷Ne nucleus. It is s...

T-invariance conditions for the differential cross sections of multiparticle multistep nuclear reactions are found with allowance for spin orientations of particles in the initial channels of such reactions. It is shown that the asymmetry coefficients for different T-parities in the differential cross sections for original and time-reversed reactio...

Some shortcomings of the approaches that are used to describe T-odd ROT and TRI asymmetries in true ternary fission via reactions involving the emission of prescission alpha particles and which are based on employing the classical method of trajectory calculations are analyzed. These shortcomings are caused by the disregard of the interference betw...

It is shown that the multiplicities and angular and energy distributions of neutrons and photons evaporated from thermalized fragments originating from the spontaneous and low-energy induced fission of nuclei, the relative yields of ground and isomeric states of final fragments, and the features of delayed neutrons emitted upon the beta decay of th...

The T-invariance condition was analyzed for the amplitude Tb,a of multiparticle multistep elastic or inelastic a → b nuclear reactions. This condition leads to the equality of the amplitude Tb,a to the amplitude \({\tilde T_{\bar a,\bar b}}\) of \(\bar b \to \bar a\) time-reversed reaction, for which the reaction operator \(\tilde T\) coincides wit...

On the basis of the theory of diagonal two-proton two-step virtual decays of spherical nuclei that was developed earlier and the superfluid model of the nucleus, the total and partial widths for the two-proton decay of the ⁴⁵Fe parent nucleus in the ground state to the ground state of the ⁴³Cr daughter nucleus were calculated along with the angular...

It is confirmed that one source of the large relative orbital momenta L of fragments in spontaneous and stimulated low-energy nuclear fission is quantum transverse zero-point wriggling vibrations of the fissioning system near its scission point. The angular distributions of fragments of low-energy photofission of actinide nuclei, calculated using t...

An analysis of low-energy true ternary (quaternary) nuclear fission leads to the conclusion that these fission modes have a sequential two-step (three-step) character such that the emission of a third particle (third and fourth particles) and the separation of fission fragments occur at distinctly different instants, in contrast to the simultaneous...

Systems of kinetic equations for decay chains of genetically related nuclei, the R-matrix theory of nuclear reactions with formation of unstable particles, and a diagram technique with Green?s function are used to study the general form for the widths of n-step statistical decays of parent nuclei that are in quasi-stationary resonance states. Condi...

A unified mechanism of the emergence of T-odd ROT- and TRI-asymmetries is proposed for describing experimental T-odd asymmetry coefficients D(θ) in the angular distributions of prescission alphaparticles that are emitted in true ternary and quaternary nuclear fission reactions induced by cold polarized neutrons. The mechanism is related to the diff...

It is shown that A. Bohr’s classic theory of angular distributions of fragments originating from low-energy fission should be supplemented with quantum corrections based on the involvement of a superposition of a very large number of angular momenta L m in the description of the relative motion of fragments flying apart along the straight line coin...

Basic dynamical effects that accompany the cold-polarized-neutron-induced binary and ternary fission of actinide nuclei and which determine the properties of T -odd asymmetries in angular distributions of various prescission and evaporated light third particles emitted in true and delayed ternary fission are analyzed on the basis of quantum-mechani...

An analysis of basicmechanisms of binary and ternary fission of nuclei led to the conclusion that true ternary and quaternary fission of nuclei has a sequential two-step (three-step) character, where, at the first step, a fissile nucleus emits a third light particle (third and fourth light particles) under shakeup effects associated with a nonadiab...

Possible orientations of the compound fissile nuclei associated with the polarization and alignment of these nuclei for the spontaneous and low-energy induced binary and ternary fission of nuclei by cold neutrons and their effect on the emergence of anisotropies and different kinds of asymmetry in the angular distributions of fission fragments and...

A brief account is given of P A Cherenkov's Voronezh years, a period during which the future Nobel laureate in physics attended school (in the village of Novaya Chigla near Voronezh) and studied at Voronezh State University. The history of the serendipitous discovery of the radiation which was to be named after him is described and its importance f...

It is shown that the coefficients D exp for all T-odd asymmetries observed experimentally in the cross sections for the reactions of cold-polarized-neutron-induced fission of nonoriented target nuclei (which involves the emission of prescission and evaporated particles) comply in shape and scale with the coefficients D theor calculated for the anal...

Since P-odd and T-odd asymmetries are generally not observed during the fissioning of unoriented target nuclei by polarized neutrons and oriented target nuclei by unpolarized neutrons, analogous asymmetries in angular distributions of products from binary and ternary fissioning of oriented target nuclei by cold polarized neutrons are thoroughly ana...

P-Odd, T-even asymmetries in angular distributions of products from the binary and ternary spontaneous fissioning of nuclei oriented in strong magnetic fields at ultralow temperature are described for the first time by means of the quantum theory of fission. Using the spin density matrix of a fissioning nucleus and considering the notable octupole...

P-odd asymmetries in binary fission of oriented target nuclei induced by cold polarized neutrons are described for the first time using methods of the quantum theory of fission. A spin matrix of the compound nucleus density is constructed with allowance for the interference of the fission amplitudes of various pairs of neutron resonances excited in...

The coefficients of P-odd, P-even, and T -odd asymmetries for a third and a fourth prescission particle emitted in the true quaternary fission of nuclei that was induced by polarized cold neutrons were studied on the basis of quantum-mechanical fission theory. By using non-evaporation (nonadiabatic) mechanisms of light-particle emission, these coef...

Induced fission reactions of fissioning compound nuclei that result from the capture of various incident particles (nucleons, γ rays, multiply charged ions) by target nuclei are investigated using the generalized nucleus model and the Wigner random matrix method. The effect produced on the fission widths of the compound nucleus by the competition b...

The problem of describing T-odd asymmetries in ternary fission reactions of oriented nuclei is solved for the first time on the basis of quantum theory. Estimates of the T-odd asymmetry coefficients in the angular distributions of the reaction products are obtained using the spin density matrix of the oriented fissioning nucleus. It is demonstrated...

On the basis of quantum-mechanical fission theory, the features of true quaternary nuclear fission are studied by treating this fission process as a sequence of three processes following one another in the course of time. The first two processes are the escape of the first and then the second of the two light particles emitted from the neck of a fi...

It is shown that the emergence of anisotropies in the angular distributions of fragments originating from the spontaneous and induced fission of oriented actinide nuclei is possible only if nonuniformities in the population of the projectionsM (K) of the fissile-nucleus spin onto the z axis of the laboratory frame (fissile-nucleus symmetry axis) ap...

T-odd asymmetries in the ternary fission of oriented target nuclei, induced by cold unpolarized neutrons and accompanied by emission of α particles, are described using quantum fission theory. The differential cross section for the reaction in question is obtained using the spin density matrix of the target nucleus by considering the Coriolis inter...

Anisotropy in the angular distributions of cascade-evaporation neutrons in center-of-mass systems emitting their fission fragments is analyzed in the context of the quantum theory of fission. It is emphasized that such anisotropy is caused not by bending but by wriggling oscillations of the fissioning nucleus in the vicinity of its point of scissio...

Differential cross sections for reactions of the true ternary fission of nuclei that was induced by cold polarized neutrons were constructed with allowance of the effect that Coriolis interaction and the interference between fission amplitudes of neutron resonances excited in fissile nuclei upon incidentneutron capture by target nuclei exerted on a...

The possibility of semiclassically describing T-even TRI-type asymmetry in ternary fission induced by polarized neutrons is considered on the basis of employing Coriolis interaction that takes into account the coupling of a light charged particle to the collective rotation of a polarized fissile nucleus. It is shown that allowance for this interact...

A comparative analysis of the results obtained by experimentally and theoretically studying T-odd asymmetries for various third particles in the true and delayed ternary nuclear fission induced by cold polarized neutrons was performed. It was confirmed that the appearance of these asymmetries was associated with the effect of rotation of a polarize...

A version of a unified quantum-mechanical description of the nature of T-odd TRI and ROT asymmetries due to the effect of the collective rotation of a polarized nucleus splitting into even and odd components of the angular distribution amplitude of prescission α particles emitted in the ternary fission of nuclei by cold polarized neutrons is consid...

Spin density matrices of neutron resonance states of a compound nucleus formed in the reaction of capture of a polarized neutron by a non-oriented target nucleus for different directions of neutron polarization vector are constructed within the quantum fission theory. The obtained spin matrices are used to calculate T-odd asymmetries in differentia...

It is demonstrated that the formation of the fissile nucleus prescission configuration with two fission prefragments connected by a neck is possible only with the simultaneous appearance of high values of relative orbital moments of the abovementioned prefragments, independently of their form. It is found that conservation of the fissile nucleus sp...

The mechanisms and the features of the main types of nuclear ternary fission (that is, true ternary fission, in which a third particle is emitted before the rupture of the fissioning nucleus into fragments, and delayed ternary fission, in which a third particle is emitted from fission fragments going apart) are investigated within quantum-mechanica...

Effects of T-odd asymmetry in ternary-nuclear-fission reactions induced by polarized cold neutrons are considered within quantum theory. It is shown that the asymmetry coefficient can be expressed in terms of experimental angular distributions of third particles in reactions induced by unpolarized neutrons. The explicit form of this coefficient mak...

Within quantum-mechanical fission theory, it is shown that, in the low-energy fission of actinide nuclei, the projection K of the spin of a fissile nucleus onto its symmetry axis is conserved as this nucleus traverses the second well of the deformation potential and the region of descent from the external fission barrier to the scission point, this...

Conditions for the appearance and observation of prescission gamma rays emitted by a fissioning nucleus prior to its separation into fission fragments were investigated within quantum-mechanical fission theory. It is shown that these conditions are realizable in the gamma decay of isovector electric giant dipole resonances in a fissile nucleus that...

The asymmetry coefficients of fragments’ angular distribution (FAD) for fission of 234, 236, 238U and 238, 240, 242Pu isotopes, induced by linearly polarized photons, have been calculated. The optimal energies for observing the polarization parts in this asymmetry are found. Based on the experimental data on FAD for 232Th photofission induced by li...

It is shown that, because of sufficiently large energy spacing between neutron resonance states (NRS-II) in the second well of the deformation potential for actinide nuclei, the Coriolis interaction, mixing the states of an axially symmetric deformed nuclei with different values of the projection K of the nuclear spin J onto the symmetry axis, is w...

Advantages and disadvantages of taking into account rotation of polarized nuclei in classical trajectory calculations of ternary fission are considered. Expressions for polarization of the fissioning deformed compound nucleus which allow for the quantum number K in the fission channel are derived.

Within quantum-mechanical fission theory, P-odd and P-even correlations in angular distributions of products of the ternary fission of nuclei that is induced by polarized cold and thermal neutrons are investigated on the basis of a nonevaporative mechanism of third-particle emission and under the assumption that a two-humped fission barrier exists....

Within quantum fission theory, angular distributions of products originating from the ternary fission of nuclei that is induced by polarized cold and thermal neutrons are investigated on the basis of a nonevaporative mechanism of third-particle emission and a consistent description of fission-channel coupling. It is shown that the inclusion of Cori...

The intrinsic mechanisms that are responsible for the pumping of high values of the spins and relative orbital angular momenta of deformed and spherical primary fission fragments and which are induced by the connection between the quantum-mechanical uncertainty principle and the shape of a fissile nucleus are investigated.

Three novel experiments in spontaneous and thermal neutron induced fission all with a bearing on angular momentum in fission are reviewed. In the first experiment it was observed that, in the reaction 235U(n, f) with incident polarized cold neutrons, the nucleus undergoing scission is rotating. This was inferred from the shift in angular distributi...

The angular distributions of fragments for photofission of even-even nuclei, induced by linearly polarized photons, have been analyzed for the first time within the quantum fission theory, taking into account the deviations of these angular distributions from A. Bohr’s formula.

A quantum version of a unified description of two T-odd effects recently observed in the ternary fission of nuclei that is induced by polarized neutrons is considered. These effects are explained by the effect of the Coriolis interaction of the rotating fissile system on the angular distributions of light charged particles in the interior and exter...

Generalization of the R-matrix theory of nuclear reactions with the use of the method of projection operators has been performed to describe the fission and cluster decays of atomic nuclei with the emission of two or three fragments with successive quantum-mechanical consideration of the fission and decay channel coupling.

The relationship between decay properties of nuclei (primarily cluster properties) and cluster-decay characteristics is discussed. Both purely microscopic and microscopically substantiated semimicroscopic and semiempirical methods are considered. The current state of the proton-, α-, and cluster-radioactivity theory is presented.

In the framework of the quantum theory of spontaneous and low-energy induced fission, the nature of quantum and thermodynamical properties of a fissioning system is analyzed taking into account adiabatic and nonadiabatic modes of motion for different fission stages. It is shown that, owing to the influence of the Coriolis interaction, the states of...

Ternary fission of the standard reaction 235U(nth,f) induced by cold polarized neutrons has been investigated. Fission fragments and light charged particles were recorded in coincidence. Following cold neutron capture the compound nucleus 236U* has spin 3- or 4-. At the saddle point of the fissioning 236U* nucleus these states are collective. They...

It is shown that consideration of the Coriolis interaction makes it possible to explain both T-odd effects observed in ternary fission induced by polarized neutrons. A possible reason for the difference in the effects observed for 233U and 235U targets is discussed.

Various interference effects governing the character of angular distributions of binary and ternary nuclear fission products and P-odd, P-even, and T-odd asymmetries in these angular distributions have been studied within the quantum theory of spontaneous and low-energy induced nuclear fission.

The quantum theory of binary and ternary fission is generalized to the case of recently observed quaternary nuclear fission. Formulas for the amplitudes of partial fission widths and angular and energy distributions of quaternary fission products are derived with allowance for strong channel coupling. The nonevaporation mechanism for formation of l...

It is shown that the large values of the orbital momenta of relative motion of fission fragments result from purely quantum effects of orientational pumping related to the uncertainty relations.

Ternary fission of the standard reaction U-235(n(th),f) induced by cold polarized neutrons has been investigated. Fission fragments and light charged particles were recorded in coincidence. Following cold neutron capture the compound nucleus U-236* has spin 3(-) or 4(-). At the saddle point of the fissioning U-236* nucleus these states are collecti...

In the framework of quantum-mechanical fission theory, the method of calculation for partial fission width amplitudes and asymptotic behavior of the fissile nucleus wave function with strong channel coupling taken into account has been suggested. The method allows one to solve the calculation problem of angular and energy distribution countation fo...

A short review is given of the recent developments in the quantum theory of low-energy fission. It is emphasized that angular anisotropy and various angular correlations of fission products are possible only if the fissioning nucleus remains nonthermalized during all the stages of fission from the saddle point to scission.

T-odd asymmetries in ternary nuclear fission are studied within the framework of quantum fission theory with a nonevaporating mechanism for formation of ternary particles. The Coriolis interaction between the orbital momentum of the ternary particle and the spin of the fissioning nucleus is shown to play a decisive role in formation of these asymme...

It is shown that anisotropy of neutron yields [W(0°)/W(90°) - 1] in the fission fragment center-of-mass system is about 10 % for both the light and the heavy fragment. The magnitude of the anisotropy depends only (apart from fragment excitation energy) upon the average initial angular momentum of the fragment (J) and is insensitive to the form of t...

A method for calculating amplitudes of partial two-proton decay widths and asymptotics of the decaying nucleus wave function is proposed, which allows the problem of description of two-proton radioactivity to be solved without a laborious procedure of matching the interior and exterior wave functions of the decaying nucleus in the three-body scheme...

It is shown that A. Bohr’s concept of transition fission states can be matched with the properties of Coriolis interaction if an axisymmetric fissile nucleus near the scission point remains cold despite a nonadiabatic character of nuclear collective deformation motion. The quantum and thermodynamic properties of various stages of binary and ternary...

Within quantum-mechanical fission theory, the angular distributions of fragments originating from the subthreshold photofission of the even-even nuclei 232Th, 234U, 236U, 238U, 238Pu, 240Pu, and 242Pu are analyzed for photon energies below 7 MeV. Special features of various fission channels are assessed under the assumption that the fission barrier...

The concept of transition fission states, which was successfully used to describe the angular distributions of fragments for the spontaneous and low-energy induced fission of axisymmetric nuclei, proves to be correct if the spin projection onto the symmetry axis of a fissile nucleus is an integral of the motion for the external region from the desc...

The two-proton decay of spherical nuclei is investigated on the basis of the formalism developed in constructing the quantum-mechanical theory of ternary fission. The proposed method for determining the amplitudes of partial widths with respect to two-proton decay and the asymptotic behavior of the wave function for a decaying nucleus makes it poss...

T-odd asymmetries in ternary nuclear fission were studied within the framework of the quantum theory of fission by using the nonevaporation mechanism for production of third particles with arbitrary spins. The Coriolis interaction of the orbital momentum of the third particle and the spin of the fissioning nucleus played a decisive role in formatio...

By using the formalism of the quantum theory of fission, the amplitudes of partial decay widths and the asymptotic behavior of the wave function for a decaying nucleus are found with allowance for open-decay-channel coupling not only for fission, but also for the binary decays of nuclei through protonic, alphaparticle, cluster, and other channels.

The evolution of a fissile nucleus from transition fission states specified at the saddle point of the deformation potential to fission states associated with prescission configurations of this nucleus and characterized by a pearlike shape of the nucleus is studied within the quantum-mechanical theory of fission processes that is based on the time-...

Within the quantum-mechanical theory of fission, wave functions for fragments of binary nuclear fission and amplitudes of partial fission widths are constructed with allowance for a strong nonsphericity of fragment-interaction potentials. It is shown that, in the strong-coupling approximation, the symmetry axes of fission fragments are oriented alo...

A version of a theoretical explanation is proposed for the recently discovered effect of T-odd correlation in ternary nuclear fission induced by polarized neutrons. It is shown that the inclusion of the Coriolis interaction between a third particle and the fissile-nucleus spin within the quantum theory of fission makes it possible to explain the ex...

Within the quantum-mechanical theory of the nuclear-fission process, the conditions of the emergence of coherent effects in the angular distributions of fragments originating from the binary and ternary fission of polarized nuclei are analyzed with allowance for the properties of transition fission states. In the case of ternary fission, the coeffi...