$^{6}$He is one of the simplest nuclei with a halo in the ground state 0$^{+}$; its study has received considerable theoretical attention [1]. In [2], an assumption was made about a halo-like structure in the isobar-analogue state of the 3.56 MeV state, 0$^{+}$ $^{6}$Li. This structure is a spatially extended halo-like structure with an alpha particle core and a proton and neutron surrounding...
One of the main directions of modern nuclear physics is the study of exotic nuclei far from the stability line, i.e. nuclei with an excess of neutrons or protons. One of the most famous representatives of exotic nuclei is halo.
In the A=8 multiplet, a halo was firstly discovered in $^{8}$B in [1] based on increased quadrupole moment. It was shown that the halo structure is $^{7}$Be core and a...
The search for the the multineutron systems is old, but still unsettled problem of the low-energy nuclear
physics. Numerous attempts of search for the existence of the tetraneutron as a bound or resonant state
have been realized using multiple approaches (e.g. uranium fission reactions, pion-induced double-chargeexchange and transfer reactions). However, no certain evidence of tetraneutron...
Abstract. We investigate the breakup of the $^{11}$Be halo nuclei on a light ($^{12}$C ) target within quantum-quasiclassical approach in a wide range of beam energy (5โ67 MeV/nucleon) including the low-lying resonances of $^{11}$Be. The obtained results are in good agreement with existing experimental data at 67 MeV/nucleon. The developed computational scheme can potentially be used for...
Measurements were carried out of the angular distributions of the differential cross sections of the reaction products 7Li+10B ELAB = 58 MeV. One of the objectives of the measurements was to compare the root-mean-square radii of the ground and excited states of nuclei obtained in the reaction. In the experiment, the angular distributions of 7Lig.s, 6Lig.s, 6Li(3.56 MeV), as well as 11B(8.56...
Analysis of cross sections of the $^7$Li+$^{10}$B elastic scattering and the transfer reaction $^7\rm{Li}+^{10}$B$\rightarrow^6$Li+$^{11}$B at the beam energy E$_{LAB}$ = 58 MeV is carried out by using the microscopic optical potential (OP) [1]. Such OP is calculated by a corresponding double folding procedure taking into account antisymmetrization effects and depends on the nucleon density...
The energy spectra of alpha particles and 6,7Li nuclei emitted at an angle of 0ยฐ in the reaction induced by a 56Fe beam (400 MeV) incident on a 238U target were measured by means of the high-resolution magnetic analyzer (MAVR setup) [1]. The resulting spectra (Fig. 1) were found to contain fast alpha particles and 6,7Li nuclei with the energy corresponding to the two-body and three-body exit...
Investigation of the influence of angular momentum and the excitation energy of the compound nucleus on the Mass-Total Kinetic Energy (M-TKE) distribution of fission fragments give important insight into the fission process. The aim of the present work is to study the influence of compound nucleus angular momentum on the M-TKE distributions of fission fragments formed in the $^{24}$Mg +...
Deviation of the cross section for the nuclear reaction X(a, b)Y from the Gamow formula due to an interaction additional to the Coulomb one in the entrance channel has been analyzed. It is shown that the reaction cross section has an oscillating structure at low energies. If the maximum of the first oscillation is close to the threshold of the channel a+X, it has a resonance behavior. To...
The description of the fission fragments (FFs) angular distributions requires the use of quantum concepts about the dynamics of the fission process. It was demonstrated [1] that during spontaneous and low-energy induced binary fission FFs near the scission point should be in cold nonequilibrium states. For the construction of FFs angular distributions, it is necessary to take into account only...
Studies of neutron transfers with the formation of neutron-excess Au isotopes in the reaction are presented for reactions 7Li ,48Ca + 197Au. Using the activation method, the formation cross sections for target-like products were measured. An assembly of several gold targets was irradiated with an ion beam 48ะกะฐ at energies 228, 257, 286 MeV. Total flux of particles passing through the collector...
In our previous publications [1-4] we presented experimental evidences of rare ternary decay mode of low excited heavy nuclei called collinear cluster tri-partition (CCT). Essential feature of this process is that some of the fission fragments (FFs) born during binary fission undergo a break-up, while they pass a solid-state foil. This break-up is delayed and occurs after the binary fission of...
Spatial parity breaking effects in the interaction of slow and resonant neutrons with Lead nucleus will be investigated. For scattering and capture processes, spin rotation, asymmetry of emitted neutrons and asymmetry of emitted gamma quanta were evaluated and compared with existing experimental data. Parity breaking effects were evaluated in the frame of the formalism of the mixing states of...
The spectroscopic factors are generally quenched relative to the occupancy numbers predicted by the independent particle model(IPM), which is quantified by the reduction/quenching factor Rs[1,2] and is associated with nucleon-nucleon correlations [3,4]. Rs extracted from knock-out reactions were found to be strongly dependent on the isospin asymmetry (ฮS = Sn- Sp / Sp- Sn for neutron/proton...
emphasized textThe differential cross sections (DCs) of theneutron transfer $^{16}$O(d,p)$^{17}$O reaction leading to the ground and first excited states of the $^{17}$O nucleus were measured at deuteron energies of 36 MeV and they used to extract the spectroscopic factors for the $^{16}$O+nโ$^{17}$O vertex[1]. In the present work, the analysis of the experimental DCs of the above...
Recent observation of mass-asymmetric fission in neutron-deficient Hg and Pt nuclei has reignite interest in studying the fission properties of heavy nuclei both theoretically and experimentally.
To study the multimodal fission of excited preactinide (Pt, Hg, Pb) and heavy actinide (Fm, Cf, No) nuclei formed in reactions with O, Ar and Ca ions at various excitation energies a series of...
A model for describing spontaneous ternary fission of heavy nuclei is presented. It follows from the suggested model that heavy nuclei have the same half-lives in spontaneous ternary and binary fission processes. The collinear cluster tripartition process observed in experiments is found to be the dominant reaction channel in spontaneous true ternary fission of heavy nuclei within our model....
The 237Np neutron-induced fission cross section was measured relative to the 235U(n, f) cross section in the energy range from 0.2 MeV to 500 MeV using the GNEIS neutron time-of-flight spectrometer and the pulsed neutron source based on the 1 GeV proton synchrocyclotron of the NRC KI - PNPI (Gatchina). The experimental setup consisted of two position-sensitive MWPC counters, which also allowed...
Nuclear fission presents a striking phenomenon where the initial spin-zero spontaneously fissioning nucleus results in primary fission fragments with significant angular momenta (2-8 ยฏh) [1]. Various theories have been proposed to explain the mechanism behind this phenomenon, differing in whether they attribute the generation of angular momentum to happen at scission point or at post-scission...
The results of measurements of fission cross sections and angular distributions of fission fragments from neutron-induced fission of 243-Am in the energy range 1-500 MeV are presented in [1]. The measurements were performed on the neutron time-of-flight spectrometer based on the GNEIS neutron complex at the 1GeV proton synchrocyclotron of the NRC "Kurchatov Institute" - PNPI (Gatchina). The...
Research into heavy-ion (HI) fusion, a key area of modern nuclear reaction physics, has flourished in recent decades pursuant to developments in accelerator technology. The primary goal of studying HI reactions is to gain knowledge about the underlying processes and how they are affected by entrance channel parameters, such as beam energy, angular momentum, and mass asymmetry. The fusion...
Description of nuclear fission is still an important problem. This is proved by the existence of various models attempting to describe maximally possible characteristics of the investigated process.
Similar goal is also faced by the model developed [1, 2] in the present study, which describes the dynamics of fission of heavy nuclei in the low- and medium-energy range. It is based on the...
Abstract
Accurate simulation of radiative capture reactions (RCRs), which hold significant importance in various areas of nuclear physics and technology, relies on precise evaluation and modeling of gamma-ray strength functions (GSF). Therefore, several phenomenological and microscopic GSF models have been developed in nuclear reaction codes for practical applications. Since theoretical GSF...
The hindrance to complete fusion is studied as a function of the charge asymmetry of colliding nuclei and orbital angular momentum of the collision. The formation of a dinuclear system (DNS) in the heavy ion collisions is calculated dynamically and its evolution is considered as multinucleon transfer between its fragments. The results prove that a hindrance at formation of a compound nucleus...
Properties of nuclear sizes, such as material and charge root-mean-square radii and density distributions of nuclear matter, provide us with basic information for understanding the structure of the nucleus [1, 2]. One of the experimental approaches to extracting these parameters, particularly for radioactive nuclei, is based on measuring the total reaction cross sections ฯR and their energy...
Mass and energy distributions of fission fragments of 237Pu compound nuclei formed in 233U(ฮฑ,f) reaction at 24 and 29 MeV incident alpha particle energy were measured at U-150M cyclotron at Institute of Nuclear Physics, Almaty, Kazakhstan using 2E method. Measured distributions at two different compound nuclei excitation energies were each decomposed into separate yields from fission modes and...
The isospin-asymmetry and its related nuclear matter properties influence most of the nuclear structure, reactions and decays. For instance, the values of the density diffuseness in finite nuclei and its anisotropy and polarization, rely on the asymmetry characteristics of the nucleon-nucleon interaction and nuclear matter at sub-saturation densities. This is related to the allowed maximum...
The experimental data on the proton elastic and inelastic scattering at energies 200-1000 MeV on the nuclei $^{28}$Si, $^{40}$Ca, $^{58}$Ni and $^{208}$Pb are investigated using the microscopic optical potential model. Such potential is based on the proton-nucleon amplitude of scattering on the bounded nuclear nucleons. The obtained parameters of the amplitude are compared with those known...
The possibilities of photonuclear experiments at $E_\gamma = (1โ4)$ MeV on collimated gamma-sources from Compton backward-scattering of laser radiation on beams of accelerated electrons are considered. The following items are discussed: operation parameters of such gamma-sources; monitoring of their gamma-beams; types of possible photonuclear experiments, including nuclear resonance...
L. D. Blokhintsev and D. A. Savin
Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow, Russia
Asymptotic normalization coefficients (ANC) are important nuclear characteristics. We discuss a method for determining ANC values from experimental data on differential cross sections of nuclear transfer reactions. The method is based on the use of the analytic...
Absolute majority of data on photonuclear, first of all photoneutron, reaction cross sections was obtained in different type experiments carried out using the beams of quasimonoenergetic annihilation photons and the beams of bremsstrahlung [1]. The methods of receiving the information on reaction cross sections are quite different. On the beams of annihilation photons the cross sections of...
There is very little experimental data on cross sections of photonuclear reactions on mercury in the literature, and for energies of the order of 50-60 MeV there is no data at all. To obtain cross sections for an equivalent quantum during the reactions of ${}^{nat}Hg(\gamma,inkp)$, a sample of natural mercury was irradiated with a beam of bremsstrahlung from the RTM-55 linear electron...
This work presents an experimental and theoretical study of photoproton reactions on erbium isotopes. Currently, the nuclear databases (EXFOR) only contain data on photoneutron reactions on a natural mixture of erbium isotopes [1] and on the isotope $^{166}$Er [2]. No data on photoproton reactions is available.
The experiment was performed by irradiating a target made of a natural mixture of...
ะ ะฝะฐััะพััะตะต ะฒัะตะผั ะฒ ัะตะพัะตัะธัะตัะบะธั ะธััะปะตะดะพะฒะฐะฝะธัั ัะฒะพะนััะฒ ะปะตะณะบะธั ัะดะตั ะพัะฝะพะฒะฝะพะต ะผะตััะพ ะทะฐะฝะธะผะฐัั ะฒััะพะบะพัะพัะฝัะต ะผะธะบัะพัะบะพะฟะธัะตัะบะธะต ะฟะพะดั ะพะดั, ะฒ ัะฐััะฝะพััะธ ab initio ะผะตัะพะดั ะพะฟะธัะฐะฝะธั ะฐัะพะผะฝัั ัะดะตั. ะะฐะธะฑะพะปะตะต ะฟะพะฟัะปััะฝัะผ ััะตะดะธ ััะธั ะผะตัะพะดะพะฒ ัะฐััะตัะฐ ัะฒะปัะตััั ะพะฑะพะปะพัะตัะฝะฐั ะผะพะดะตะปั ัะดัะฐ ะฑะตะท ะธะฝะตััะฝะพะณะพ ะบะพัะฐ (NCSM). ะญัะฐ ะผะพะดะตะปั ะดะฐะตั ะฒะพะทะผะพะถะฝะพััั ะดะพะฒะพะปัะฝะพ ัะพัะฝะพ ัะฐัััะธััะฒะฐัั ะฒะพะปะฝะพะฒัะต ััะฝะบัะธะธ ะพัะฝะพะฒะฝัั ะธ ัะตะทะพะฝะฐะฝัะฝัั ัะพััะพัะฝะธะน...
In order to study relative yields of 209Bi(ฮณ,xn) reactions, samples of 99.99% pure bismuth-209 were exposed at LINAC-200 electron beam with tungsten convertor at energies 35, 40, 45, 50, 55, 60 MeV. Activities of obtained products of photonuclear reactions with different neutron multiplicity, from (ฮณ,2n) to (ฮณ,7n) were measured. Relative yields normalized to 206Bi yield were calculated....
Activation techniques for studying nuclear reactions producing high-spin isomeric states are discussed. It is demonstrated that some specific properties of a beam of low-energy alpha particles that make this beam especially interesting for obtaining and studying these states.
Results of the investigations of the yield of high-spin and low-spin isomers in reactions 41K(ฮฑ,n)44Sc, 86Sr...
In this work, the D(d, p)T and D(d, n)$^{3}$He transfer reactions are studied by means of the microscopic multichannel cluster approach in the oscillator representation [1โ3]. These reactions are of great interest for pure and applied physics. Their total and partial astrophysical S factors are calculated. The contributions of the different channels are discussed, the most important...
Recently, in a laser plasma with an average electron temperature
ฮ ~ 1 keV and a lifetime ฯ โ 0.3 ns, it was found out the stimulation of de-excitation of nuclear isomers (SDENI) Re-186m (half-life T = 2ร10E5 years) to the ground state of the Re-186 nuclei (T = 90 hours) with a probability P โ 1ยท10E(โ7), which apparently occurred through an intermediate trigger level with a half-life of ~ 10...
ะะทะฐะธะผะพะดะตะนััะฒะธะต ะฑัััััั ะฝะตะนััะพะฝะพะฒ ั ัะดัะพะผ $^{10}B$ ะฟัะธ ัะฝะตัะณะธัั ะพั 3 ะดะพ 7ย ะัะ, ัะพะฟัะพะฒะพะถะดะฐััะตะณะพัั ะฒัะปะตัะพะผ ัะดัะฐ $^{3}H$, ะธััะปะตะดัะตััั ั ัะตะปัั ะฒัะดะตะปะตะฝะธั ัะตะฐะบัะธะธ ั ัะพะถะดะตะฝะธะตะผ ัะดัะฐ $^{8}Be^{*}$ ะฒ ะฒะพะทะฑัะถะดะตะฝะฝะพะผ ัะพััะพัะฝะธะธ. ะญัะฐ ัะตะฐะบัะธั ะฒัะดะตะปัะตััั ะฝะฐ ัะพะฝะต ััะตั ัะฐััะธัะฝะพะน ัะตะฐะบัะธะธ ั ะฒัะปะตัะพะผ ััะธัะพะฝะฐ ะธ ะดะฒัั ะฐะปััะฐ-ัะฐััะธั. ะะพะดะตะปะธัะพะฒะฐะฝะธะต ะธะพะฝะธะทะฐัะธะพะฝะฝัั ะฟะพัะตัั ะฒัะพัะธัะฝัั ัะดะตั $^{3}H$ ะธ $^{4}He$ ะฒ ัะฒะตัะดัั ะธ ะณะฐะทะพะฒัั ...
The first 10 excited states of the carbon isotope were studied in terms of single-particle and collective models of excitation. Experimental cross sections were obtained by the well-known $\vartriangle$EโE method. Elastic scattering data were analyzed using an optical model including a nucleusโnucleus interaction potential, while inelastic scattering data were processed using the...
The study of photonuclear reactions is an important fundamental task for obtaining information about the structure of the nucleus and the nature of the nuclear forces. At present, only reactions involving the escape of one or two neutrons in the giant dipole resonance region are well studied. We have studied the flux-weighted average cross sections of (ฮณ,xn) reactions on natural iridium at...
The 7He nucleus was studied using the 6He(d, p)7He reaction in inverse kinematics at 29AยทMeV 6He beam delivered by the ACCULINNA-2 fragment separator (FLNR, JINR). The registration of neutrons from 7He โ n +6 He decay made it possible to derive the 7He ground state parameters, the decay energy of 0.38(2) MeV and width of 0.11(3) MeV. The forward-backward asymmetry in the neutron emission from...
New approach based on combination of the optical model with the modified optical potential and the classical trajectories is proposed for calculations of the effective matter radii of the identical colliding nuclei. The example of the angular distribution for 6Li + 6Li elastic scattering is shown in Fig. 1a. The plot of the value , where is the diagonal element of the S-matrix, is shown in...
In heavy-ion induced reactions, the interaction mechanism is primarily governed by the projectile beam energy and angular momentum ($L$) of the composite system. The angular momentum brought in by the projectile have significant influence on the fission barriers [1-3]. The effects of $L$ on fission have been less investigated due to the difficulty of producing the same compound nucleus (CN)...
The differential cross-sections of the 13C(ฮฑ, ฮฑ0)13C reaction were measured at three angles (130ยฐ, 150ยฐ and 170ยฐ) in the energy range of 2.0-7.0 MeV. The thin layer of 13 ะก deposited to the beryllium backing was used as a target. The thickness and enrichment of the target were determined by the ion beam analysis methods. The effect of the carbon build-up was taken into account during the data...
Experimental data in the reaction 40Ar+9Be at projectile energy 36 MeV per nucleon obtained at the wide-aperture magnetic mass separator COMBAS were analyzed to investigate the competition between different collision reaction mechanisms in the Fermi energy region. As was shown in our previous papers velocity distributions of the forward-emitted fragments in the reactions at this energy range...
In this work, we present the results of studying nucleon transfer processes in the
reactions 48 Caย +ย 197 Au, 48 Caย +ย 9 Be at energies above the Coulomb barrier. The
experiments were performed at the Flerov Laboratory of Nuclear Reactions,
Joint Institute for Nuclear Research, Dubna. A 48 Ca beam with an energy of 400
MeV was accelerated by the U-400 cyclotron and transported to the...
In order to study the exotic structures in unstable nuclei at around N = 8, we develop a silicon + CsI(Tl) detection array with large acceptance[1,2], which is suitable for the transfer reactions induced by radioactive beams on the proton and deuteron targets in inverse kinematics. First of all, 57(7)% d-wave and 19(7)% s-wave intruder components in the g.s. of 12Be are deduced from a new...
Heavy-ion reactions at Fermi energies are a tool to produce new isotopes far from stability line. Previous experiments show that the production of neutron-reach isotopes is enhanced when the heavy target is used instead of the light one. In this report we compare isotope distributions calculated in transport-statistical approach BNV-SMM with the three frequently used models: empirical EPAX...
Theoretical analysis of experimental data on the ternary fission of $^{252}$Cf is performed in the semi-classical trajectory approach. The energy and angular distributions, total kinetic energies of the fragments in the ternary fission of $^{252}$Cf are obtained in this model using the Monte-Carlo simulations. The calculations well reproduce these experimental data with the same set of the...
Double Side Silicon Detector (DSSD) based spectrometer of the DGFRS-2 setup has been applied in a different heavy ion induced complete fusion nuclear reactions leading to formation of superheavy nuclei. Nuclear reactions with 48Ca, 40Ar, 54Cr projectiles were used [1,2]. Materials of206Pb, natYb, 232Th, 238U, 242Pu, 243Am were used as targets. We report about different stability tests during...
In our previous publications [1-4], we discussed various manifestations of the decay channel of low excited heavy nuclei, called collinear cluster tri-partition (CCT). The break-up of the fission fragment was observed while the fragment passes a solid-state foil. The bulk of the results were obtained in the framework of the so-called missing mass method when only two fragments are directly...
The study of nucleon and cluster transfer reactions makes it possible to obtain information on the structure of the investigated nuclei (clusters, neutron halo, etc.) and its manifestation in nuclear reactions [1]. This work continues our systematic studies of nucleon and cluster transfer mechanisms in reactions with various projectiles and targets (for example, d + $^{9}$Be [2], $^{3}$He +...
This paper presents the results of measuring fission fragments in 48Ca+238U reactions using a time-of-flight system developed at the MAVR facility (the experimental setup is shown in Fig. 1a). A microchannel plate (MCP) detector was used to determine the mass of the resulting fission fragments, which offers high temporal resolution and high efficiency in registering heavy charged particles. A...
Modern nuclear reaction studies show that in next eight years it will be an almost twofold increase in the consumption of radionuclides that are part of radiopharmaceuticals used in both diagnostic and therapeutic methods of nuclear medicine [1]. Today, one of the most promising radionuclide is terbium, whose radioactive isotopes can be used both diagnostic and therapeutic procedures in...
