In [1-3] the virtual mechanism of ternary fission of the compound nucleus $(A, Z)$, formed by the capture of the thermal neutron by target-nucleus $(A-1, Z)$ as the two-stage process was suggested. At the first stage light particle $(A-A_{LP},Z-Z_{LP})$ with kinetic energy close to the Coulomb barrier height is emitted from the nucleus $(A, Z)$ with the forming of the virtual state of the...
Triple collinear fission of a weakly excited compound fissile nucleus is analyzed on the basis of a sequential two-stage mechanism associated at the first stage with double fission of this nucleus with the formation of two fission fragments, and at the second stage with double fission of one of these fragments. In this case, the presentation of coldness of fission fragments at the first and...
In series of the photo-fission reactions, namely, $^{235, 238}$U(γ, f), $^{232}$Th(γ, f), $^{242}$Pu(γ, f) we have found that some part of the fission fragments (FFs) are presumably born in the state of the fission isomer with the yield Y ≈ $10^{-3}$ binary fission and with the lifetime $\tau_{isom}$ > 400 nsec [1, 2]. A binary break-up of such fragments was observed when they pass through a...
In the past, there were multiple attempts to find the so-called “true ternary fission” i.e. ternary fission with comparable masses of the fragments. So far, it has not been done, at least not in the frame of the traditional experimental approaches. In a series of our experiments, we have observed ternary partition of the heavy nuclei [1, 2] when one of the fragments of binary fission undergoes...
In the present work, the $^{3}$H(d, n)$^{4}$He fusion reaction being of interest for both fundamental and applied physics is studied at low energies. Dynamics of the reaction is described by using the microscopic multichannel cluster approach in the oscillator representation [1–3]. The total and partial cross sections for the studied reaction in terms of the astrophysical $S$ factors are...
Одним из наиболее характерных следствий кластеризации в легких ядрах является наличие вращательных полос со структурой α+кор. Наиболее хорошо изученным с этой точки зрения является ядро 20Ne, благодаря низкой энергии связи α-частицы. В то же время структура возбужденных состояний соседних самосопряженных ядер до сих пор является предметом обсуждения, даже для такого хорошо изученного ядра, как...
В работе [1] были представлены результаты анализа спектра 7Не, заселямого в реакции 6Не(d,p) в инверсной кинематике. Для регистрации нейтронов из распадов 7Не → 6He + n и 7Не → 4He + 3n был использован массив нейтронных детекторов, расположенных на расстоянии 3.5 метров за мишенью, при этом заряженные продукты распада (4,6He) детектировались тонким сцинтиллятором установленным на расстоянии 80...
The structure of excited states and even their energy spectrum for the 12C nucleus, oddly enough, is still the subject of consideration [1, 2]. The problem is that a number of poorly identified broad resonance states lying above the Hoyle state (7.65 MeV, 0+) and having an α-cluster structure overlap significantly. Against their background there are a number of levels lying below the nucleon...
The 7Li nucleus has a pronounced cluster nature as α+t. However, the one-nucleon component of the ground state is also of interest for a more complete understanding of the structure of the nucleus. Also it may be important in the nuclear-astrophysical processes of the Big Bang, such as the reaction 7Li(3H,4He), which leads to the 7Li nucleus destroy and a change in the 6Li/7Li abundance ...
Представлены результаты анализа распределений амплитуд импульсов, измеренных при регистрации спектра DT-нейтронов детектором с алмазным чувствительным элементом.
In heavy-ion reactions a lot of different isotopes are produced. Different models to predict their cross-sections exist. In this report the results of calculations in the modified transport-statistical approach of isotope distributions of forward-moving fragments for reactions with different projectiles from 18O to 64Ni with energies from 35 to 140 MeV per nucleon on two targets : 181Ta and...
В представленной работе исследовалось образование радиоактивных нуклидов при облучении мишеней металлического скандия естественного состава протонами с энергией 160 МэВ. В гамма-спектрах облученных мишеней выделены активности 38S, 38,39Cl, 41Ar, 42,43K, 43,44Sc и 45Ti. Сечения изученных реакций оказались равными σ(38S)=6.3×10–3 мбн, σ(38,39Cl)=2.2 и 0.34 мбн, σ(41Ar)=0.76 мбн, σ(42,43K)=8.8...
The $^{48}$Ca + $^{208}$Pb reaction is distinguished by its unique combination of advantages in heavy-ion fusion studies, as both interacting partners are doubly magic nuclei. Moreover, the $^{208}$Pb target provides a cold fusion pathway, while the neutron-rich $^{48}$Ca projectile provides a significant neutron excess, favoring the formation of neutron-rich compound nuclei.
The survival...
Измерены угловые распределения упругого рассеяния ядер ${}^{40,48}$Ca с энергией 400 МэВ на ядрах ${}^{197}$Au. Эксперименты проводились на циклотроне У-400 Лаборатории ядерных реакций Объединенного Института Ядерных Исследований. Идентификация продуктов ядерной реакции осуществлялась с использованием $ΔE-E$ методики. Экспериментальные данные проанализированы в рамках квазиклассического...
Dynamical decription of the multinucleon transfer reactions 48Ca+208Pb, 50Ti+208Pb and 40Ar+209Bi in the framework of dinuclear system model is presented. The system of master equations with phenomenological transition coefficients is solved for treatment of the nucleon tranfer process. The results of calculations are in good agreement with the recent experimental data obtained at FLNR...
В продолжение ранее выполненной работы [1], в данной работе на основе дифракционной теории Глаубера проведен анализ упругого рассеяния адронов (протонов, π^± - и K^± -мезонов) на ядрах 7Ве и 8В при промежуточных энергиях. Данные расчеты выполнены в диапазоне переданных импульсов 0.002≤ |t| ≤ 0.05 (ГэВ/с)2, что соответствует кинематике экспериментов, выполняемой для ряда легких ядер,...
Deuteron-proton elastic scattering is considered in the multiple-scattering-expansion model. Four reaction mechanisms are included into consideration: one-nucleon exchange, single scattering, double scattering, and delta-isobar excitation in an intermediate state. The model calculates the reaction amplitude, which makes it possible to find the angular dependence of both the differential cross...
The analysis of experimental data obtained in the reaction 40Ar+9Be at an incident beam energy of 36 MeV/nucleon on the magnetic separator COMBAS was carried out with the aim of studying competition between different reaction mechanisms in the Fermi energy region. Special attention was paid to velocity distributions of forward-emitted fragments since they contain important information about...
Nowadays applying of multinucleon transfer reactions (MNT) in collisions between heavy nuclei are supposed to be a promising approach to produce new neutron-rich nuclei including nuclei near the N = 126 shell closure. The investigation of the properties of these nuclei is very important for understanding of nucleosynthesis processes. To reach the «island of stability» using of heavy systems in...
Pairing is a key feature of the nucleon-nucleon (NN) interaction that leads to the characteristic $J^\pi = 0^+$ of the nuclear ground state in even-even nuclei and the characteristic odd-even staggering in the binding energies of nuclei.
In this contribution, I will discuss how the two-nucleon transfer reactions allow us to investigate the properties of pair strength. The basic idea is that...
Recently, there has been significant progress in the use of ab inito approaches for theoretical studies of nuclear structure, which is why there is increasing interest in the structure of the lightest exotic nuclei, the description of which is an important test of ab inito approaches.
The direct (in particular $(d,p)$) reactions are actively used to study nuclei beyond neutron stability. ...
В работе проведен анализ данных, полученных в реакциях с малонуклонными системами при различных энергиях [1-8]. Обнаружена зависимость полученных в этих работах значений синглетных длин рассеяния ($a_{np}$) от относительного импульса синглетной np-системы и третьей заряженной частицы при соответствующей кинематике реакции. Обнаруженная зависимость может быть объяснена в рамках Дибарионной...
В настоящее время в теоретических исследованиях свойств легких ядер важное место занимают ab initio методы описания атомных ядер, то есть подходы использующие реалистические нуклон-нуклонные потенциалы. Базовым среди этих методов является оболочечная модель ядра без инертного кора (NCSM). Эта модель дает возможность с хорошей точностью рассчитывать энергии и волновые функции основных и...
В работе [1] выдвинута гипотеза о том, что расхождение в экспериментальных значениях длины нейтрон-нейтронного рассеяния $a_{nn}$, полученных в реакциях с тремя частицами в конечном состоянии, может быть связано с влиянием 3$N$-сил. Можно предположить, что подобный эффект будет наблюдаться в случае измерения низкоэнергетических характеристик $pp$-взаимодействия ($a_{pp}$ и $E_{pp}$) в реакциях...
Явление мюонного катализа традиционных ядерных реакций синтеза, заключается в увеличении скорости и числа реакций синтеза за единицу времени жизни отрицательно заряженного мюона, находящегося в зоне взаимодействия ядер [1]. Прямые расчёты полных сечений реакций синтеза с корректным учётом кулоновского взаимодействия между ядрами и ядрами и лептонами в условиях когда сильное взаимодействия не...
The 239Pu, 240Pu and 242Pu neutron-induced fission cross sections were measured relative to the 235U(n, f) cross section in the energy range from 0.3 MeV to 500 MeV using the GNEIS neutron time-of-flight spectrometer at the 1 GeV proton synchrocyclotron of the NRC KI - PNPI (Gatchina). The experimental setup consisted of two position-sensitive MWPC counters, which also allowed simultaneous...
One of the actual problems of modern nuclear physics is the study of the interaction mechanism of nuclei and the study of competing processes in their interaction. Study of competition between compound nucleus fission and quasifission in heavy-ion-induced reactions and its dependence on the reaction entrance channel are important for picking up the right target-projectile combination for the...
Pre–fission neutron spectra influence the partitioning of fission energy between excitation energy and total kinetic energy of fission fragments. It might be assumed that the (n,xnf) and (p,xnf) neutron contribution, i.e. PFNS shapes might depend on the entrance channel. For incident neutron energies from fission threshold up to En ~20 MeV prompt fission neutron spectra (PFNS) of 238U(n,F)...
Recent research has primarily focused on fusion reactions induced by heavy-ion collisions involving projectiles such as $^{51}$V and $^{50}$Ti as potential pathways to extend the known isotopic ranges and to explore new elements. The synthesis pathways of superheavy elements are modeled using the dinuclear system (DNS) approach [1, 2]. The DNS model comprehensively calculates the capture cross...
Angular anisotropy of secondary neutrons was evidenced in neutron emission spectra (NES) of 239Pu+n in 1972, and in prompt fission neutron spectra (PFNS) of 239Pu(n, F) in 2019, it might be predicted for 238,40,241.242Pu(n, F) PFNS. In case of NES angular anisotropy is due to direct excitation of collective levels and pre-equilibrium/semi-direct mechanism (states in the continuum are excited)...
Recent experimental and theoretical studies have shown that it is the clustering mechanism that underlies the formation of various fission modes of heavy nuclei [1-4]. The ability to model locally strong and Coulomb interactions of nucleons at the nuclear scale using a new distributed approach and the development of high-performance computing allow a better understanding of the details of the...
Study of heavy-ion induced nuclear reactions has been an active area of investigation for last couple of decades [1-3]. In the present work, the excitation function of fusion-evaporation residues populated through complete fusion (CF) and incomplete fusion (ICF) for 18O + 103Rh system are measured in the energy range of 3 to 6 Mev/A. The off-line γ-ray spectroscopy associated with high purity...
Spontaneous ternary decay of the 252Cf was observed in series of experiments carried out in Flerov Lab. of Nuclear Reactions, JINR [1-3]. In those experiments, the existence of a new type of ternary decay in the reaction 235U(n𝑡ℎ,f) and 252Cf(sf), namely collinear cluster tri-partition (CCT), was reported. It is also observed that spontaneous fission products with the mass number around...
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 collision of two heavy nuclei can generate a significantly large reaction angular momentum. This is because heavy-ion projectile beams ($Z > 4$) can transfer more $L$ to the nucleus in a given reaction compared to light-ion beams....
The $^{238}$U($^{54}$Cr,4n)$^{288}$Lv and $^{242}$Pu($^{50}$Ti,3-4n)$^{288,289}$Lv reactions have been studied at the gas-filled separator DGFRS-2 at the SHE Factory at Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research. Three new isotopes were discovered: two α-decaying nuclei $^{288}$Lv with α-particle energy E$_{α}$ = 11.08 MeV and half-life T$_{1/2}$ = 2.0 ms,...
Fission of heavy nuclei induced by neutrons of low and intermediate energies (up to 100 MeV) typically occurs at relatively low angular momentum. As a result, the anisotropy of the angular distribution of fission fragments with respect to the direction of the incident neutron's motion is determined by the distribution of the projection K of the spin of the fissioning nucleus onto the axis of...
The Geant4 [1-3] low energy nuclear models are used to simulate final states in hadron- and ion-induced inelastic collisions with nuclei in high and moderate energy generators. The pre-compound model [4] ensures a seamless transition from the kinetic reaction stage (governed by high energy inelastic interaction) to the equilibrium phase (described by statistical deexcitation models). The...
The recent experimental results on the excitation function measurements for light particle emission in several target nuclei of mass region A=159-185 with heavy ion (HI) beams (12C, 14N,16O, and 19F) at low energy below 5 MeV/nucleon are found in disagreement with the compound theory-based statistical models. This discrepancy between experimental data and statistical model predictions led to...
Электрофизические источники нейтронного излучения на базе линейных ускорителей заряженных частиц являются важным инструментом современной экспериментальной физики. Нейтронные генераторы применяются для получения таких ядерно физических данных как микроскопические сечения взаимодействия, уровни возбуждения ядер и др. При этом, чем точнее известен энергетический спектр нейтронов, испускаемых...
Neutron scattering by exotic nuclei is a class of reactions that cannot now be directly studied experimentally. Resonance proton scattering of exotic nuclide on a thick target in inverse kinematics (TTIK) is an elegant and powerful experimental method that provides, an opportunity to infer the properties of neutron scattering on exotic nuclei based on studies of observed isobaric-analog state...
В данной работе представлен теоретический анализ реакции обмена зарядами $^{40}$Ca($^{18}$O,$^{18}$F)$^{40}$K при энергии 275 МэВ, выполненный в рамках единого подхода, учитывающего как прямой механизм обмена мезонами (DME), так и двухступенчатые процессы передачи нуклонов (n→p и p→n). Использован борновский метод искаженных волн (DWBA), при этом для структурных входных данных применена...
Представлены результаты измерения дифференциального сечения образования мгновенных гамма-квантов в неупругих взаимодействиях 14.5 МэВ нейтронов с ядрами железа. Измерения проведены в редакции интегральных экспериментов методом времени пролета на нейтронном генераторе НГ-150М, работающем в импульсном режиме, с использованием однокристального гамма-спектрометра со сцинтиллятором NaI(Tl)...
In this work presents the results of activation measurements of the cross sections for the formation of target-like fragments in multinucleon transfer (MNT) reactions in collisions of $^{48}$Ca and $^{40}$Ca nuclei with a $^{197}$Au target nucleus at energies close to the Coulomb barrier. The main attention is paid to the study of the effect of neutron excess in $^{48}$Ca on the...
The study of the multifragmentation process gives experimental information about the nuclear spinodal region. The experiment has been performed with the 4pi-setup FASA [1], installed on the external beam of the superconducting accelerator Nuclotron in Dubna.
The relative angle correlations of intermediate mass fragments have been studied for the 12C + Au collisions at 22 GeV. Strong...
Since the discovery of the nuclear component of cosmic rays, the nuclear emulsion (NTE) method has been a powerful tool for studying the composition and fragmentation of relativistic nuclei at high-energy accelerators. The potential of this approach was first demonstrated in the 1970s using NTE layers exposed to beams of nuclei with energies of several GeV per nucleon, accelerated at the JINR...
Экспериментальное исследование фотоядерных реакций на средних и тяжелых ядрах позволяет изучать особенности возбуждения и распада гигантского дипольного резонанса (ГДР). Для исследования были выбраны четные по протонам химические элементы: эрбий (Z=68), диспрозий (Z=66), палладий (Z=46), молибден (Z=42). Они имеют довольно много стабильных изотопов, что позволяет проследить изменение сечений...
New cross sections of photoneutron reactions $^{52}Cr(\gamma,2n)^{50}Cr$, $^{68}Zn(\gamma,1n)^{67}Zn$ and $^{68}Zn(\gamma,2n)^{66}Zn$ not determined before experimentally were obtained at the first time using the experimental-theoretical method for evaluation of photoneutron partial reaction cross-section meeting physical criteria of reliability method [1]. This method was proposed to solve...
Ядерные данные о взаимодействии гамма-квантов с тяжелыми ядрами необходимы для решения большого числа прикладных и фундаментальных задач. Сечения фотонейтронных реакций и реакции фотоделения используются при разработке нейтронных источников для подкритичных систем, а также для разработки систем транмутации ядерных отходов, создания пучков радиоактивных ядер, получения экзотических ядер...
In this study experiments were performed at bremsstrahlung end-point energies of 10-23 MeV with the beam from the MT-25 microtron using of the γ-activation technique. The electron energies were in range of 10-23 MeV with an energy step of 1 MeV. To produce gamma radiation, a radiator target made of tungsten, which is a common convertor material, was used. To remove the remaining electrons from...
Медицинские изотопы рения (186Re, 188Re, 189Re) - перспективные радионуклиды для использования в сравнительно новом методе ядерной медицине «тераностике». В настоящее время 186Re получают в реакции 185Re(n, γ)186Re из мишеней, обогащенных 185Re, однако при использовании такого подхода, сложно добиться высокой радионуклидной чистоты этого изотопа. Основным способом получения 188Re является...
The report is devoted to unique recent experiments on measuring the fully differential cross section of the reaction p+He -> p+e+He+ at a proton energy of 75 keV and low energy transfer to the atom. The presented theoretical and numerical calculations show the important role of the pickup mechanism
В настоящей работе представлены результаты экспериментального исследования возбуждения изомерных состояний изотопов ${}^{195,197}$Hg и ${}^{198,200}$Au, образованных в фотоядерных реакциях на природной смеси изотопов ртути под действием тормозного излучения с максимальной энергией 55 МэВ. Измерения проводились активационным методом [1] на ускорителе электронов РМ-55 НИИЯФ МГУ [2]. Изомерные...
При моделировании электромагнитных процессов фотоядерными реакциями ((γ, 1n), (γ, 2n)...) часто пренебрегают, поскольку фотоядерные сечения сопоставимы с электромагнитными γ-взаимодействиями только в области гигантского дипольного резонанса. Однако ядерные процессы способны поглотить γ-кванты значительно большей энергии, чем атомные электромагнитные процессы, поэтому в ряде задач моделирования...
Создана и исследуется установка для изучения реакций быстрых нейтронов с энергией свыше 1 МэВ с легкими ядрами $^{10}\text{B}$, $^{11}\text{B}$ и $^{9}\text{Be}$ c вылетом ядра $^{3}\text{H}$ или $^{4}\text{He}$ и электрон-позитронной пары. Установка исследуется на источниках нейтронов на базе ускорителей протонов и электронов и включает в себя позиционно-чувствительные детектор нейтронов на...
Выполнено экспериментальное и расчетное исследование образования возбужденных состояний ядер $^{7}\text{Li} ^{*}$ и $^{8}\text{Be}^{*}$ во взаимодействии быстрых нейтронов с ядром $^{10}\text{B}$ при энергии свыше 1 МэВ, сопровождающихся вылетом ядер $^3\text{H}$ и $^4\text{He}$. Экспериментальные данные сравниваются с величинами ионизационных потерь ядер-спектаторов $^{3}\text{H}$ и...
There were considered in [1–3] some issues of experimental study of photonuclear reactions under γ-quanta with energies Eγ in the region of excitation of E1 giant resonance in atomic nuclei with spectrometry of emitted fast neutrons for the γ-source from collimated Compton backscattering at the National Center for Physics and Mathematics (NCPhM, Sarov, Russia [4]). In this report for heavy...
For γ-quantum energies in the region of E1 giant resonance in atomic nuclei, there were analyzed:
• requirements for (γ, n 0;1;2)-experiments with fast neutron spectrometry on the base of results of the works [1, 2];
• parameters of γ-sources from Compton backscattering High Intensity γ-ray Source (HIγS, Durham, USA [3]) and National Center for Physics and Mathematics (NCPhM, Sarov, Russia...
The study presents a new method for determining the critical neck in nuclear fission, based on the analysis of fragment spin characteristics. The key difference from other approaches, such as [1,2], lies in using experimental data on fragment spin distributions [3] instead of the conventional analysis of mass distributions. This choice is motivated by the greater sensitivity of spin...
The characteristics of various nuclear processes are rather simple to calculate in statistical model [1-4]. In particular, the transition-width distribution is described by the Porter–Thomas equation, there are no correlations between different partial widths, the strength function of $\beta$-transitions $S_{\beta}(\textit{E})$ depends smoothly on energy, and the ratios of the amplitudes for...
In this work, we studied the total reaction cross sections for the $^{10,11,12}$Be nuclei on the $^{28}$Si target by the 4π method based on the registration of the prompt γ quanta and neutrons accompanying the interaction using the multidetector spectrometer. It was found that the total reaction cross sections for the $^{11}$Be nuclei are significantly larger than those for $^{10}$Be. Along...
A numerical solution of the time-dependent Schrodinger equation [1, 2] is applied in studying the dynamics of the the nucleons and the alpha-clusters transfer in the reaction ${}^{40}$Ar+${}^{nat}$Ag at energy 285 МeV. The evolution of wave functions for outer nucleons is used to describe multi-neutron and multi-proton transfer channels. In addition the evolution of the alpha-cluster wave...
Modern approaches to describe the dynamics of nuclear fission make extensive use of the Langevin formalism [1,2], which effectively accounts for the stochastic nature of the process. However, the problem of correctly determining the parameters of the random force in this approach remains unresolved. This issue becomes particularly relevant for low-energy fission, where quantum effects [3] play...
Six-detector silicon spectrometer of charged particles with their separation by ΔE-E method was made. Spectrometer consisted of telescopes with extremely low registration threshold of tritons (0.6 MeV) and 3He nuclei (1.3 MeV). Energy distributions of tritons and 3He produced in 6Li(d,xt) and 6Li(d,x3He) reactions were measured at tandem accelerator EGP-10 (VNIIEF) at Ed=4–10 MeV energy range...
Relative yields of photonuclear reactions on 59Co and 89Y were measured with the beam of bremsstrahlung γ-radiation at the energies of 40-130 MeV. The experiments were performed with the beam from the electron linear accelerator LINAC-200 using the γ-activation techniques. The theoretical relative yields were calculated by using the computer code TALYS-2.0 [1] with different models of the...
Understanding the interaction between high-energy photons and atomic nuclei is essential for exploring nuclear structure and reaction mechanisms. Advances in accelerator technology now make it possible to simulate and analyze complex photonuclear processes under controlled laboratory conditions, enabling researchers to study a wide range of isotopes, including terbium.
The current...
