Excited Nuclei Research Articles

Timing Performances of SDD as Photodetector Candidate for Proton Therapy Application

In the proton therapy, charged particles interact with tissue depositing dose in the tumor, providing enhanced tumor coverage compared to conventional radiotherapy. However, proton range uncertainties limit the full exploitation in clinical practice of the localized dose deposition. Range and dose monitoring in real time would be beneficial to deliver safer and more effective treatments. A possible solution is to use the signature of high-energy (2–8 MeV) prompt gamma rays, produced naturally along the beam path by excited nuclei. In this article, we study the timing capability of the silicon drift detector (SDD) as a photodetector candidate to be used for the scintillator readout for high-energy gamma rays detection. The peculiar drift mechanism affects the time needed for the photogenerated charge inside the SDD volume to approach the collecting electrode. As a result, the detector output signal shows a rise time limiting usually its timing performances when used with scintillators. In this work, we first developed a simulator to predict the drift time values as a function of charge generation position. Next, we performed the experimental characterization of the SDD timing performances by directly irradiating it with laser light. We carried out spectroscopy measurements for the assessment of the electronics noise of the detector in two readout configurations: 1) single anode and 2) merged anodes. Finally, we experimentally evaluated the timing performances of the SDD at the signal levels expected in the target application, showing sub-ns timing resolution.

Temperature dependence of cluster decay

A universal decay law (UDL) for light cluster decay of excited nuclei is formulated by fitting the UDL half-lives to those evaluated within an excitation energy-dependent double folding model (DFM). The half-lives are evaluated within a preformed cluster model. The excitation energy dependence is introduced both in the energy of the emitted cluster and in the interaction potential through the density distributions of the interacting nuclei. The half-lives are found to decrease when the difference between the excitation energies of the parent and daughter nuclei, ΔE⁎> 0, increases, with the reduction being a few orders of magnitude for higher values of ΔE⁎. This can be of importance for nucleosynthesis calculations of heavy elements formed in extremely hot environments, as well as in highly energetic heavy-ion collisions. The UDL for excited nuclei is used to provide an estimate of the enhancement in the cluster decay rates of thermally excited nuclei such as those produced in r-process nucleosynthesis.

Statistical model calculation of the compound nuclear fission timescale in fusion-fission reactions

In the decay of an excited heavy nucleus, both the fission or evaporation residue (ER) cross sections and the fission time are determined by the competition between the various evaporation channels and fission. Statistical model (SM) calculations for several heavy-ion-induced fusion-fission reactions are presented which reproduce the fission or ER excitation functions. The corresponding calculated fission times are found to depend upon the compound nuclei and their excitation energies. The multichance fission probabilities and the corresponding fission times are also obtained, and they are shown to depend sensitively on the shell correction energies and the neutron separation energies of the compound nuclei involved. The experimental neutron multiplicities are reproduced by adjusting the saddle-to-scission transition time interval. An additional delay time for compound nuclear formation is found necessary to fit the experimental neutron multiplicities for a system with higher entrance channel mass symmetry.

Measurement of the parity-odd angular distribution of γ rays from polarized neutron capture on Cl35

We report a measurement of two energy-weighted γ cascade angular distributions from polarized slow neutron capture on the Cl35 nucleus, one parity-odd correlation proportional to sn⃗·kγ⃗ and one parity-even correlation proportional to sn⃗·kn⃗×kγ⃗. A parity-violating asymmetry can appear in this reaction due to the weak nucleon-nucleon interaction, which mixes opposite parity S- and P-wave levels in the excited compound Cl36 nucleus formed upon slow neutron capture. If parity-violating (PV) and parity-conserving (PC) terms both exist, the measured differential cross section can be related to them via dσdΩ∝1+Aγ,PVcosθ+Aγ,PCsinθ. The PV and PC asymmetries for energy-weighted γ cascade angular distributions for polarized slow neutron capture on Cl35 averaged over the neutron energies from 2.27–9.53 meV were measured to be Aγ,PV=(−23.9±0.7)×10−6 and Aγ,PC=(0.1±0.7)×10−6. These results are consistent with previous experimental results. Systematic errors were quantified and shown to be small compared to the statistical error. These asymmetries in the angular distributions of the γ rays emitted from the capture of polarized neutrons in Cl35 were used to verify the operation and data analysis procedures for the NPDGamma experiment, which measured the parity-odd asymmetry in the angular distribution of γs from polarized slow neutron capture on protons.5 MoreReceived 1 October 2021Accepted 17 May 2022DOI:https://doi.org/10.1103/PhysRevC.106.015504©2022 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasNuclear spin & parityNuclear tests of fundamental interactionsPolarization phenomenaRadiative captureProperties20 ≤ A ≤ 38TechniquesParticle sources & targetsNuclear Physics

Beyond the harmonic approximation description of wobbling excitations in even-even nuclei with frozen alignments

The wobbling motion in even-even nuclei is investigated by means of a collective Hamiltonian constructed from a semiclassical treatment applied to a triaxial rotor with a rigidly aligned pair of quasiparticles. The limits of distinct wobbling regimes are discussed in connection to the dynamic evolution of the wobbling excitations and corresponding electromagnetic properties. Model calculations are performed for the description of transverse wobbling bands in $^{130}\mathrm{Ba}, ^{134}\mathrm{Ce}$, and $^{136,138}\mathrm{Nd}$ nuclei.

Modeling survival probabilities of superheavy nuclei at high excitation energies

This work investigated the first-chance survival probabilities of highly excited compound superheavy nuclei in the prospect of synthesizing new superheavy elements. The main feature of our modelings is the adoption of microscopic temperature dependent fission barriers in calculations of fission rates. A simple derivation is demonstrated to elucidate the connection between Bohr-Wheeler statistical model and imaginary free energy method, obtaining a new formula for fission rates. The best modeling is chosen with respect to reproducing the experimental fission probability of $^{210}$Po. Systematic studies of fission and survival probabilities of No, Fl, Og, and $Z$=120 compound nuclei are performed. Results show large discrepancies by different models for survival probabilities of superheavy nuclei although they are close for $^{210}$Po. We see that the first-chance survival probabilities of $Z$=120 are comparable to that of Fl and Og.

Study of the Cross-Section for the 122Te(γ, n)121Te Reaction by the Activation Method

Relevance. The study of photonuclear reactions plays a defining role in the formation of modern ideas about highlocalized collective excitations in nuclei of the giant resonance type. The giant dipole E1-resonance (GR) is the main feature in γ-quantum absorption cross-sections of nuclei. The presence of isotopes with multiple isotopes makes it possible to trace the evolution of GR characteristics from changes in the number of neutrons in the nuclei. One such element is tellurium. Purpose. The purpose of this research is an experimental and theoretical study of the cross-section of 122Te(γ, n)121Te reaction in the region of giant E1-resonance energies. Methods. The study of the cross-section of (γ, n) reaction on 122Te isotope was performed on the bremsstrahlung γ-beam of the M-30 microtron of the Institute of Electronic Physics of the National Academy of Sciences of Ukraine. The yield curves were measured in the range of maximum gamma-quantum energies Eγmax=10-18 MeV. The reaction cross-section was calculated by the inverse matrix method. When registering the reaction products, an activation technique was used, while the gamma activity of the products was recorded by the spectrometric method. The theoretical calculations of the cross-section for the 122Te(γ, n)121Te reaction were performed using the TALYS-1.9 software package. Results. The measured experimental yield ratios of the 122Te(γ, n)121Te і 130Te(γ, n)129Te d= Yn121 /Yn129 = f (E max) reactions allowed the experimental cross-section for the 122Te(γ, n)121Te reaction to be calculated. The cross-section has a single hump shape with a maximum at an energy of ~ 15.3 MeV. It was approximated by the Lorentz curve with the parameters δ0 =(274.1±2.1) MB, Е0 (15.27±0.10) MeV, Г0 =(4.76±0.08) MeV. The cross-section obtained was compared with similar cross-sections for 126Te and 130Te isotopes, as well as with theoretical calculations according to the TALYS-1.9 program. Conclusions. The obtained cross-section for the 122Te(γ, n)121Te reaction is consistent with the evolution of the parameters of (γ, n) reaction cross-section on tellurium isotopes 130Te(γ, n)129Te with a change in the number of neutrons. The theoretical approaches used are satisfactorily consistent with the experimental data. This agreement indicates the main contribution of the statistical mechanism to the cross-section of the considered (γ, n) reaction and a relatively small contribution of semi-direct processes

Multiparticle-hole excitations in nuclei near N = Z = 20: $$^{41}$$K

This experimental study of high-spin structure near \(N = Z = 20\) nuclei was focused on \(^{41}\)K, but will also mention three newly observed \(\gamma \) transitions in \(^{41}\)Ca observed in the same reaction. High-spin states were populated using the \(^{26}\)Mg(\(^{18}\)O, \(p2n\gamma \))\(^{41}\)K and \(^{26}\)Mg(\(^{18}\)O, \(3n\gamma \))\(^{41}\)Ca reactions. The experiment was carried out at an incident beam energy of 50 MeV at the Florida State University (FSU) John D. Fox Superconducting Linear Accelerator Laboratory and used the FSU high-purity germanium detector array. The \(^{41}\)K level scheme was extended to 12325 keV, possibly with J\(^{\pi }\) = 25/2\(^-\) or 27/2\(^+\), by means of 25 new transitions and that of \(^{41}\)Ca to 9916 keV. Linear polarization and a measure of angular distribution results are also reported and used to provide information on the spins and parities of several states in the \(^{41}\)K level scheme. The results have been compared to the spsdpf cross-shell FSU shell model interaction calculations. The theoretical results from configurations involving no or one additional nucleon promoted from the sd to the fp shell agree relatively well with the energies of known states, while those that involve multi-particle excitations paint an interesting and complex picture of interplay between single-particle excitations, collective pairing, and deformation. This presents an interesting challenge for future theory.

Effect of dissipation coefficient of the K coordinate in dynamical modeling of nuclear fission of 178W produced in fusion reaction

In this paper, a stochastic approach based on two-dimensional dynamical model was used to simulate the fission process of the excited compound nucleus [Formula: see text]W produced in [Formula: see text] reaction. In the dynamical calculations, the elongation parameter of the nucleus was used as the first dimension and the projection of the total spin of the compound nucleus onto the symmetry axis, [Formula: see text], considered as the second dimension. The average pre-fission multiplicities of neutron, light charged particles and the total kinetic energy of the fission fragments were calculated for [Formula: see text]W and the results of calculations compared with the experimental data over a wide range of excitation energy. In the dynamical calculations, dissipation was generated through the chaos weighted wall and window friction formula and the dissipation coefficient of [Formula: see text], was considered as a free parameter and its magnitude inferred by fitting measured data on the average pre-fission multiplicities of neutron and proton for the compound nucleus [Formula: see text]W. It was shown that the results of calculations are in good agreement with the experimental data by using the dissipation coefficient of [Formula: see text] in the range [Formula: see text]. It was also shown that the results of calculations with [Formula: see text] provide a better agreement with the experimental data than with a deformation-dependent dissipation coefficient. Furthermore, it was also shown that differences between the results of calculations for the total kinetic energy of the fission fragments calculated by using different values of dissipation coefficient of [Formula: see text] are small.

Effective field theory of pairing rotations

Low-energy effective theories have become a powerful tool in nuclear physics and elsewhere in the past several decades. This paper describes a large amount of experimental data in this framework as ``pairing rotational bands'' with just a few parameters. The pairing rotational tensor is akin to a moment of inertia in the gauge space of two interacting superfluids. Its eigenvectors rotate with respect to the ($N$,$Z$) coordinate system, and they approximately point in the direction of the valley of $\ensuremath{\beta}$ stability and perpendicular to it. Combining superfluidity with deformation shows that the lowest-lying excitations in atomic nuclei are model-independent and based on emergent symmetry breaking.

Substance P Increases the Excitability of Dorsal Motor Nucleus of the Vagus Nerve via Inhibition of Potassium Channels

Increases in the substance P (SP) concentration in the medial portion of the dorsal motor nucleus of the vagus nerve (mDMV) in the brainstem are closely associated with chemotherapy induced nausea and vomiting (CINV). However, the underlying cellular and molecular mechanisms of action are not well understood. In this study, we investigated the effects of SP on mDMV neurons using whole-cell patch-clamp recordings from rat brainstem slices. Application of different concentrations of SP induced tonic and phasic responses. Submicromolar concentrations of induced an inward shift of the holding current by increasing membrane input resistance. The response was mimicked by acidification of the extracellular solution and inhibited by a neurokinin type 1 receptor antagonist. These responses have equilibrium potentials close to the K+ equilibrium potential. In addition, a TWIK-related acid-sensitive K+ channel 3 (TASK-3) inhibitor, PK-THPP, induced responses similar to those produced by submicromolar SP concentrations. Micromolar concentrations of SP facilitated γ-aminobutyric acid (GABA) release but diminished glutamate release; these changes were blocked by a GABAB receptor antagonist and a neurokinin type 3 receptor antagonist, respectively. In current-clamp recordings, submicromolar SP concentrations increased neuronal excitability by depolarizing membrane potentials. However, neither the increase in SP concentration to the micromolar range nor the addition of GABAA and ionotropic glutamate receptor antagonists affected neuronal excitability. Thus, SP increases the excitability of mDMV neurons by inhibiting K+ conductance.

Simulation of the fission process of the excited compound nuclei Rn210 and Fr215 produced in fusion reactions within the framework of the modified statistical model

In the framework of the modified statistical model there have been simulated fission process of the excited compound nuclei $^{210}\mathrm{Rn}$ and $^{215}\mathrm{Fr}$ produced in $^{16}\mathrm{O}+^{194}\mathrm{Pt}$ and $^{19}\mathrm{F}+^{196}\mathrm{Pt}$ reactions and calculated the evaporation residue cross section, the fission cross section, the fission probability, the average prescission neutron multiplicity, the mean fission time, and the anisotropy of fission fragments angular distribution as a function of excitation energy. The classical collective motion of the excited compound nuclei about the ground state, the temperature dependence of the location, the height of fission transition points, and the projection of the total spin of the compound nucleus onto the symmetry axis $K$ have been considered in the statistical calculations. A constant nuclear dissipation was applied in the statistical calculations. In the statistical calculations, the temperature coefficient of the effective potential $k$ and the scaling factor of the fission-barrier height ${r}_{s}$ were considered as a free parameter and their magnitudes inferred by fitting measured data on the evaporation residue cross section and the fission cross section for the excited compound nuclei $^{210}\mathrm{Rn}$ and $^{215}\mathrm{Fr}$. It was shown that the results of calculations are in good agreement with the experimental data by using appropriate values for these parameters equal to $k=0.0160\ifmmode\pm\else\textpm\fi{}0.0050\phantom{\rule{0.28em}{0ex}}\mathrm{Me}{\mathrm{V}}^{\ensuremath{-}2}$ and ${r}_{s}=1.0030\ifmmode\pm\else\textpm\fi{}0.0020$ for $^{210}\mathrm{Rn}$ and $k=0.0065\ifmmode\pm\else\textpm\fi{}0.0040\phantom{\rule{0.16em}{0ex}}\mathrm{Me}{\mathrm{V}}^{\ensuremath{-}2}$ and ${r}_{s}=1.0040\ifmmode\pm\else\textpm\fi{}0.0015$ for $^{215}\mathrm{Fr}$. Furthermore, by using appropriate values of parameters $k$ and ${r}_{s}$ have been calculated the average prescission neutron multiplicity, the fission probability, the mean fission time, and the anisotropy of fission fragments angular distribution for the nuclei $^{210}\mathrm{Rn}$ and $^{215}\mathrm{Fr}$. Comparison of the theoretical data with the experimental data were shown that the modified statistical model is well able to reproduce different experimental data. Although, at high excitation energies the results of calculations for the anisotropy of fission fragments angular distribution and fission probability are slightly lower than the experimental data.

Low-energy monopole strength in spherical and axially deformed nuclei: Cluster and soft modes

Background: Several recent experiments report significant low-energy isoscalar monopole strength, below the giant resonance, in various nuclei. In light $\ensuremath{\alpha}$-conjugate nuclei, these low-energy resonances were recently interpreted as cluster vibration modes. However, the nature of these excitations in neutron-rich nuclei remains elusive.Purpose: The present work provides a systematic analysis of the low-energy monopole strength in isotopic chains, from neon to germanium, in order to monitor and understand its nature and conditions of emergence.Methods: We perform covariant quasiparticle random phase approximation calculations, formulated within the finite amplitude method, on top of constrained relativistic Hartree-Bogoliubov (RHB) reference states.Results: Neutron excess leads to the appearance of low-energy excitations according to a systematic pattern reflecting the single-particle features of the underlying RHB reference state. With the onset of deformation, these low-energy resonances get split and give rise to more complex patterns, with possible mixing with the giant resonance. At lower energy, clusterlike excitations found in $N=Z$ systems survive in neutron-rich nuclei, with valence neutrons arranging in molecularlike orbitals. Finally, at very low energy, pair excitations are also found in superfluid nuclei, but remain negligible in most of the cases.Conclusions: The low-energy part of the monopole strength exhibits various modes, from cluster vibrations ($\ensuremath{\approx}$5--10 MeV) to components of the giant resonance downshifted by the onset of deformation, including soft modes ($\ensuremath{\approx}$10--15 MeV) as well as pair excitation ($<$5 MeV), with possible mixing, depending on neutron excess, deformation, and pairing energy.

Spin inhibition in γ -decay probabilities for states above Sn in Sm and Dy nuclei

When a compound nucleus is formed at an excitation energy above the neutron-separation threshold, it is assumed that its de-excitation will proceed via neutron emission. However, if the excited nucleus is in a high-spin state, but does not have enough excitation energy to conserve angular momentum by either photon emission after neutron emission or relative angular momentum carried off by the neutron, the nucleus will de-excite via $\ensuremath{\gamma}$-emission instead. This effect, the spin inhibition, provides an insight into the structure of the compound nuclei and can aid the understanding of the distribution of the populated spin states in a compound nuclear reaction. In this work, the effects of spin inhibition on the $\ensuremath{\gamma}$-decay probabilities from states in $^{146,147}\mathrm{Sm}$ and $^{160}\mathrm{Dy}$ are presented. For high-spin states above the ${S}_{n}$, spin inhibition is able to suppress neutron emission, and de-excitation via $\ensuremath{\gamma}$-ray emission is observed for states up to 3 MeV above the ${S}_{n}$.

Rare isotope formation in complete fusion and multinucleon transfer reactions in collisions of Ca48+Cm248 near Coulomb barrier energies

Within the framework of the dinuclear system model, the reaction mechanisms for synthesizing target-like isotopes from Bk to compound nuclei Lv are thoroughly investigated in complete and incomplete fusion reaction of $^{48}$Ca +$^{248}$Cm around Coulomb barrier energies. Production cross-section of $^{292,293}$Lv as a function of excitation energy in fusion-evaporation reactions and target-like isotopic yields in multinucleon transfer reactions are evaluated, in which a statistical approach is used to describe the decay process of excited nuclei. The available experimental data can be reproduced well with the model reasonably. The products of all possible formed isotopes in the dynamical pre-equilibrium process for collision partners at incident energy $E_{\rm lab}$ = 5.5 MeV/nucleon are exported, systematically. It is found that the quasi-fission fragments are dominant in the yields. The optimal pathway from the target to compound nuclei shows up along the valley of potential surface energy. The effective impact parameter of two colliding partners leading to compound nuclei is selected from head-on collision to semi-central collision with $L$ = 52 $\rm \hbar$. The timescale boundary between complete fusion and multinucleon transfer reactions is about 5.7$\times 10^{-21}$ s with effective impact parameters. Synthesis cross-section of unknown neutron-rich actinides from Bk to Rf have been predicted around several nanobarns.

Specific features of capture reactions of real and virtual α-particles by 6Li and 7Li isotopes

The article examines the features of the interaction of virtual and real α-particles with isotopes 6Li and 7Li with the formation of the ground and excited states of 10B and 11B nuclei. The multiparticle shell model is used to describe the structures of nuclei. The significant difference in the excitation spectra of 10B and 11B nuclei in the capture of real and virtual α-particles is explained by the structural features of these nuclei and different mechanisms of capture of α-particles. Real α-particles are captured in reactions (α, γ), and virtual ones - in lithium cluster transfer reactions. In both boron isotopes, the first decay channel is the α-particle, then there is an energy range of several MeV until the next decay channel with the emission of particles. Moreover, in this energy range, the S-factors are anomalously small. If the excited levels lie above the threshold for the breakup of the nucleus with the emission of certain particles a, then the S-factors turn out to be related to the partial widths of the decay Га. In contrast to spectroscopic factors, which do not depend on energy and are determined only by the structure of the initial and final states, the partial Γ-widths depend on the energy which the particles are emitted with. It is shown that, in a narrow energy range from the first threshold for the emission of particles to the second threshold, the cross sections for the excitation of residual nuclei by real and virtual α-particles differ significantly. Narrow beams of γ-quanta formed with large cross sections in reactions of radiative α-capture can be used for diagnostics of thermonuclear plasma.

Temperature and density effects on the two-nucleon momentum correlation function from excited single nuclei

Two-nucleon momentum correlation functions are investigated for different single thermal sources at given initial temperature $(T)$ and density $(\rho)$. To this end, the space-time evolutions of various single excited nuclei at $T$ $= 1 - 20$ $MeV$ and $\rho$ = 0.2 - 1.2 $\rho_0$ are simulated by using the thermal isospin-dependent quantum molecular dynamics $(ThIQMD)$ model. Momentum correlation functions of identical proton-pairs ($C_{pp}(q)$) or neutron-pairs ($C_{nn}(q)$) at small relative momenta are calculated by $Lednick\acute{y}$ and $Lyuboshitz$ analytical method. The results illustrate that $C_{pp}(q)$ and $C_{nn}(q)$ are sensitive to the source size ($A$) at lower $T$ or higher $\rho$, but almost not at higher $T$ or lower $\rho$. And the sensitivities become stronger for smaller source. Moreover, the $T$, $\rho$ and $A$ dependencies of the Gaussian source radii are also extracted by fitting the two-proton momentum correlation functions, and the results are consistent with the above conclusions.

Signature of fusion suppression in complex fragment emission

The effect of weak binding of $^{9}\mathrm{Be}$ on complete fusion has been explored through the study of complex fragment emission in $^{20}\mathrm{Ne}+^{9}\mathrm{Be}$ reaction. The yields of the fragments $^{6,7}\mathrm{Li}$ and $^{7,9}\mathrm{Be}$ emitted from the excited compound nucleus $^{29}\mathrm{Si}^{*}$ have been compared with the respective statistical model predictions. Emission of same fragments from another close-by compound nucleus $^{28}\mathrm{Si}^{*}$ at similar excitation energy, formed by the fusion of two strongly bound nuclei, $^{16}\mathrm{O}+^{12}\mathrm{C}$, has been studied for comparison. It has been observed that for the system $^{16}\mathrm{O}+^{12}\mathrm{C}$, the yields of $^{6,7}\mathrm{Li}$ and $^{7,9}\mathrm{Be}$ fragments are close to the predictions of the statistical model. However, for the $^{20}\mathrm{Ne}+^{9}\mathrm{Be}$ system, although the experimental yield pattern follows the statistical model prediction, there is substantial reduction in yield for all detected fragments. These observations have been attributed to the suppression of complete fusion in $^{20}\mathrm{Ne}+^{9}\mathrm{Be}$ system due to the weak binding of $^{9}\mathrm{Be}$, a dynamical effect which is not incorporated in the conventional statistical models. It is the first time that a clear signature of the suppression of complete fusion in light systems involving weakly bound nucleus has been observed in complex fragment emission from fully equilibrated composite produced in fusion well above the barrier.

Angular momentum transfer in multinucleon transfer channels of O18+Np237

The angular momentum of a primary excited compound nucleus produced in multinucleon transfer reaction is an important quantity to evaluate cross sections to synthesize neutron-rich heavy-element nuclei as well as for surrogate reaction studies. The mechanism is, however, not enough understood due to the lack of detailed experimental data. In the present study, we determined the angular momentum of primary excited nuclei, $^{237,238,239}\mathrm{Np}, ^{238,239,240}\mathrm{Pu}$, and $^{239,240,241}\mathrm{Am}$, produced in the multinucleon transfer channels of the $^{18}\mathrm{O}+^{237}\mathrm{Np}$ reaction. With this aim, angular distributions of fission fragments with respect to the axis perpendicular to the reaction plane were measured for each compound nucleus. The distributions show an anisotropy exhibiting an enhanced yield on the reaction plane. They are well reproduced by a saddle-point model, from which the average angular momentum is derived in the model framework. The angular momentum increases with the compound-nucleus mass, thus the number of nucleons exchanged, but shows a saturating trend toward heavier compound nuclei. These results are the first ones to point to the dependence of the angular momentum on the transfer channels.

Monte Carlo simulations of $$\gamma $$-directional correlations and their application on FIFRELIN cascades

Angular distribution and correlation measurements are an essential part in nuclear structure experiments, especially when spectroscopic information of a specific nucleus is unknown. In most cases, the experimental determination of the spins, parities of the studied nuclear states, as well as the possible mixing between two electric/magnetic multipoles of a transition are determined using angular correlation measurements. In this work, the full effect of directional {\gamma}-correlations is simulated, by using the formal theory of angular distributions. The density matrix formalism along with its multipole expansions called statistical tensors is employed, enabling to perform a full simulation of the angular correlation effects in a cascade of an arbitrary number of {\gamma} transitions. A triple {\gamma} angular correlation simulation is demonstrated for the first time. The present approach was coupled with the Monte Carlo code FIFRELIN, which can simulate the de-excitation of fission fragments or of excited nuclei after neutron capture. It provides a complete description of the spatial distributions of all the {\gamma} rays in the cascade, that can be used for simulation purposes in various applications both in nuclear and particle physics. The potential for a novel approach in data analysis of angular correlation measurements is discussed thoroughly.