Level Density Parameter Research Articles

Semiclassical level density parameter with collective enhancements in nuclei

In this work, we calculate the level density parameter for several nuclei by deploying the semiclassical trace formula for spherically symmetric harmonic oscillator potential with spin-orbit interactions, which describes the quantum shell effects in terms of the classical periodic orbits. With the usage of recently proposed Laplace like formula of level density parameter by Canbula et al., the effects of collective rotations and vibrations as well as deformations in nuclei are incorporated. The comparison of our results with the experimental ones show a good agreement. Later on, the study is also extended to the calculation of nuclear level density and survival probability in several superheavy nuclei (SHN).

Excitation energy and angular momentum dependence of the nuclear level density parameter around A≈110

Neutron kinetic energy spectra in coincidence with low-energy $\ensuremath{\gamma}$-ray multiplicities have been measured around $A\ensuremath{\approx}110$ in the $^{16}\mathrm{O}+^{93}\mathrm{Nb}$ and $^{20}\mathrm{Ne}+^{93}\mathrm{Nb}$ reactions in a compound nuclear excitation energy range of $\ensuremath{\approx}90--140$ MeV. The excitation energy (temperature) dependence and the angular momentum (spin) dependence of the inverse level density parameter $k$ have been investigated by comparing the experimental data with statistical Hauser-Feshbach calculations. In contrast to the available systematic in this mass region, the inverse level density parameter showed an appreciable increase as a function of the excitation energy. The extracted $k$ values at different angular momentum regions, corresponding to different $\ensuremath{\gamma}$ multiplicities, also showed an overall increase with the average nuclear spins. The experimental results have been compared with a microscopic statistical-model calculation and found to be in reasonable agreement with the data. The results provide useful information to understand the variation of nuclear level density at high temperature and spins.

Updated nuclear level density parameters of 153Sm nucleus within the back-shifted Fermi gas model

The present work re-evaluates the level density parameter a, asymptotic level density parameter aasy, and back-shifted energy parameter E1 within the back-shifted Fermi gas model (BSFG) for the 153Sm nucleus. This reevaluation is based on the experimental nuclear level scheme extracted from the ENSDF library, the average level spacing at the neutron binding energy (D0 value), and the latest updated nuclear level scheme obtained from an experimental gamma cascade experiment, which was performed at the Dalat Nuclear Research Reactor using the thermal neutron beam. The updated values of the BSFG level parameters are: (1) a=18.09±0.25 MeV-1and E1=-0.92±0.07 MeV for the energy-independent level density parameter; and (2) aasy=15.00±0.20 MeV-1and E1=-0.81±0.08 MeV for the energy-dependent level density parameter. It has been found that the total nuclear level densities calculated using these updated parameters agree with the experimental data better than those using parameters taken from the nuclear reference database RIPL-3. These updated parameters are more accurate and reliable than those extracted from RIPL-3 and are, therefore, highly recommended for all the applications hereafter.

Estimations of level density parameters by using artificial neural network for phenomenological level density models

The main aim of this study is to develop accurate artificial neural network (ANN) algorithms to estimate level density parameters. An efficient Bayesian-based algorithm is presented for classification algorithms. Unknown model parameters are estimated using the observed data, from which the Bayesian-based algorithm is predicted. This paper focuses on the Bayesian method for parameter estimations of Gilbert Cameron Model (GCM), Back Shifted Fermi Gas Model (BSFGM) and Generalised Super Fluid Model (GSM), which are known as the phonemological level density models. Obtained level density parameters have been compared with the Reference Input Parameter Library for Calculation of Nuclear Reactions and Nuclear Data Evaluations (RIPL) data. R values of the Bayesian method have been found as 0.9946, 0.9981 and 0.9824 for BSFGM, GCM and GSM, respectively. In order to validate our results, default level density parameters of TALYS 1.95 code have been changed with our newly obtained results and photo-neutron cross-section calculations of the 117Sn(γ,n)116Sn, 118Sn(γ,n)117Sn, 119Sn(γ,n)118Sn and 120Sn(γ,n)119Sn reactions have been calculated by using these newly obtained level density parameters.

Electrochemical mineralization of abattoir wastewater with continuous system

This study aims to determine the effects of initial pollutant concentration level (1/1–1/4), flow rate (10–40 mL/min), NaCl concentration (0.1–1 M), pH (3–9) and current density (4.73–23.67 mA/cm2) parameters on the removals of total suspended solids, total organic carbon, chemical oxygen demand, total nitrogen and color for economic treatment of cattle-abattoir wastewater using mesh-type Ti/Pt anodes with continuous EO system. Total suspended solids, total organic carbon, chemical oxygen demand, total nitrogen and color analyses were carried out according to photometric method, catalytic oxidation method, closed reflux colorimetric method, nitrogen cell test method and platinum–cobalt method, respectively. The effluent chloride levels were analyzed according to the argentometric titration method. According to results, all operational parameters had an impact on removal efficiencies but the most effective parameters on energy consumption were NaCl concentration and applied current density. Although two possible system conditions were determined according to removal efficiencies the operating conditions with the lowest energy consumption are considered to be optimal. The optimum operating conditions were determined as NaCl concentration of 1 M, CD of 4.73 mA/cm2, initial pH of 7.03, reaction temperature of 25 °C and FR of 10 mL/min. Under these conditions removal efficiencies (%) for total suspended solids, total organic carbon, chemical oxygen demand, total nitrogen and color were found as; 98.28, 93.03, 97.44, 95.53 and 99.80, respectively. The energy consumption values were calculated as 2.42 kWh/kg COD and 19.43 kWh/m3. The approximate cost to treat 1 m3 wastewater was calculated as $ 6.43. The kinetic behavior abided by a pseudo-first-order model.

Investigation of α-induced Reaction on Copper Isotopes for Energy Range of 15-50 Mev

The present work was done on alpha induced reaction mechanics on two natural coppers isotopes for the energy range of 15 to 30 Mev were investigated. The reaction channels for the total cross section 63Cu (α, n) 66Ga, 65Cu (α, 2n)67Ga, 63Cu(α, pn) 65Cu and 65Cu(α, n)68Ga were studied. The experimental data of reaction cross section COMPLETE code have been used. The aim study was compared experimental and theoretical reaction cross section both compound and pre-compound reaction and know the property, the reaction mechanism of the projectile particle reacts with target nuclei. The theoretical result was obtained from international atomic energy agency, exchange format data source. We understood the reaction mechanisms and the property of fragment particles during the reaction. Level density parameter and exaction number were varied to become good agreement between the calculated and measured data. In this study different dependency reaction cross section, the projectile energy was observed between the production of 67Ga and 65Zn. In alpha induced reaction with copper isotopes 66Ga, 67Ga, 68Ga and 65Zn are produced. Normally the calculation using a COMPLET code provides good outcome for the reaction cross-section of alpha induced reaction on low projectile energy. During the study of the reaction compound and pre-equilibrium reaction are occurred but direct reaction was almost not expected. Direct reaction is required to very large amount of energy.

The Study of Neutron Induced Reaction on Manganese Reaction Cross-Section at Intermediate Energy

The general neutron induced reaction cross sections with the projectile neutron energy are being studied. As a result of this, the compound nucleus is formed through de-excitation of the selected nuclei by emitted particles γ and 2n with the reaction cross section at intermediate energy. The production of residual nuclide by neutron induced reaction on the selected nuclei has been investigated by using computer code projection angular-momentum coupled evaporation Monte Carlo code (PACE4). Dependence of Reaction Cross Section for Projectile Neutron with Different K Values on Target 55Mn in the Energy Range (0.5 - 3.42) Mev and Dependence of Reaction Cross Section for Projectile Neutron with Different K Values on 55Mn Target in the Energy Range (11.5 - 38.5) Mev. Then, the theoretical estimated value compared with the Experimental value the data which obtained from International Atomic and Energy Agency, Exchange format. Results show us the reaction cross section vs energy of projectile neutron with target nucleus Manganese and the emitted particles were γ and 2n respectively with new residual nuclei, i.e. 56Mn and 54Mn, in addition to this the best fit K values are 10 and 8 for each channels respectively. Finally the level density parameter is the dominant parameter that can influence the reaction cross section from the outcome of this software by varying with free constant parameter (K). i.e., 8, 10 and 12.

Calculation of the shape of energy-ordered spectra for investigations of the nuclear continuum

The nuclear continuum may potentially be investigated by means of fusion-evaporation reactions in combination with the $Hk$ technique. The $\ensuremath{\gamma}$ radiation in such experiments can be analyzed using energy ordering which produces complex spectra. A method for computing the shape of the energy-ordered spectra is presented and benchmarked by reproducing simulated data. The spectrum shape computation is applied to experimentally relevant cases and is used for extracting the level density parameter from simulations. Furthermore, the calculation shows to be useful for the characterization of nuclear phase transitions.

Evidence for the reduction of nuclear level density away from the β -stability line

The isospin dependence of nuclear level density has been investigated by analyzing the spectra of evaporated neutrons from excited $^{116}$Sn and $^{116}$Te nuclei. These nuclei are populated via $p$ + $^{115}$In and $^{4}$He + $^{112}$Sn reactions in the excitation energy range of 18 - 26 MeV. Because of low excitation energy, the neutron spectra are predominantly contributed by the first-chance decay leading to the $\beta$-stable $^{115}$Sn and neutron-deficient $^{115}$Te as residues for the two cases. Theoretical analysis of the experimental spectra have been performed within the Hauser-Feshbach formalism by employing different models of the level density parameter. It is observed that the data could only be explained by the level density parameter that decreases monotonically when the proton number deviates from the $\beta$-stable value. This is also confirmed by performing a microscopic shell-model calculation with the Wood-Saxon mean field. The results have strong implication on the estimation of the level density of unstable nuclei, and calculation of astrophysical reaction rates relevant to $r$- and $rp$-processes.

Temperature and isospin dependence of the level-density parameter in the A≈110 mass region

$\ensuremath{\alpha}$-Particle evaporation spectra were measured at backward angles in $^{16}\mathrm{O}+\phantom{\rule{0.16em}{0ex}}^{94,100}\mathrm{Mo}$ reactions at multiple beam energies. Inverse level-density parameter, $K$, was determined for Cd nuclei of different isospins by simulating high-energy tail of the measured $\ensuremath{\alpha}$-particle evaporation spectra with statistical model code pace2. An overall increasing behavior of the $K$ value is observed with increasing temperature in the range of 1 to 2.5 MeV. It is observed that in the temperature region below 1.8 MeV, the parameter $K$ is higher for the neutron-rich nuclei by around 1 MeV. Semiclassical calculations were performed which treat single-particle level density of neutron and proton on different footing and this can account for the isospin effects. These calculations reproduce the $K$ values as determined from the statistical model analysis of $\ensuremath{\alpha}$-particle evaporation spectra. Present results clearly demonstrate the isospin dependence of the level-density parameter as conjectured by theoretical works.

Cross sections of 56Fe(n, p)56Mn, 55Mn(n, p)55Cr, 52Cr(n, p)52V, 56Fe(n, α)53Cr, 55Mn(n, α)52V and 52Cr(n, α)49Ti reactions using phenomenological level density models from threshold to 20 MeV

56Fe(n,p)56Mn, 55Mn(n,p)55Cr, 52Cr(n,p)52V, 56Fe(n, α)53Cr, 55Mn(n, α)52V and 52Cr(n, α)49Ti reactions are evaluated using four phenomenological nuclear level density models from reaction threshold to 20 MeV. The calculated data is compared with the experimental nuclear reaction data from EXFOR database. Statistical factors H, D and R are computed to identify the best fit. Level density parameters are adjusted for further improvement of the fitting. Back shifted Farmi-gas model gives a resemblance of neutron-induced 56Fe, 55Mn and constant temperature Fermi-gas model gives a closeness for 52Cr reaction with our new parameter values.

The interplay between the nuclear level density and the separation energy of rotating superheavy nucleus Z = 119 at low temperature regime

The temperature dependence of the level density parameter and the neutron separation energy are determined under statistical assumptions with regard to the excitation energy using the statistical model code developed in FORTRAN language. The quadrupole deformation parameter and the inverse level density parameter are coinciding well with the experimental results concerning the available literatures. The interplay between the level density and the particle separation energy is displayed graphically to locate the possible neutron magicity and found N=176 suits well at low temperature regime. The excitation energy for the possible formation of 119295 is predicted as 33.3 MeV.

Measurement and analysis of nuclear γ -ray production cross sections in proton interactions with Mg, Si, and Fe nuclei abundant in astrophysical sites over the incident energy range E=30–66 MeV

Gamma-ray production cross section excitation functions have been measured for $30$, $42$, $54$ and $66$ MeV proton beams accelerated onto targets of astrophysical interest, $^{nat}$C, C + O (Mylar), $^{nat}$Mg, $^{nat}$Si and $^{56}$Fe, at the Sector Separated Cyclotron (SSC) of iThemba LABS (near Cape Town, South Africa). The AFRODITE array equipped with 8 Compton suppressed HPGe clover detectors was used to record $\gamma$-ray data. For known, intense $\gamma$-ray lines the previously reported experimental data measured up to $E_{p}\simeq$ $25$ MeV at the Washington and Orsay tandem accelerators were extended to higher proton energies. Our experimental data for the last 3 targets are reported here and discussed with respect to previous data and the Murphy \textit{et al.} compilation [ApJS 183, 142 (2009)], as well as to predictions of the nuclear reaction code TALYS. The overall agreement between theory and experiment obtained in first-approach calculations using default input parameters of TALYS has been appreciably improved by using modified optical model potential (OMP), deformation, and level density parameters. The OMP parameters have been extracted from theoretical fits to available experimental elastic/inelastic nucleon scattering angular distribution data by means of the coupled-channels reaction code OPTMAN. Experimental data for several new $\gamma$-ray lines are also reported and discussed. The astrophysical implications of our results are emphasised.

Level Densities of Nuclei with Z = 112–120

Level densities of superheavy nuclei with Z = 112–120 in the ground state and at the saddle point are calculated using single-particle spectra obtained in a macroscopic and microscopic model based on the Woods–Saxon single-particle potential. Level density parameters are calculated by fitting the results with the expression of a Fermi gas. The role of shell correction and pairing effects in the behavior of the level density parameter in the ground state and at the saddle point is studied. The results from calculations are compared to phenomenological expressions. The ratio of the level density parameter at the saddle point to its values ​​in the ground state is presented.

Excitation functions of 58Ni(n, charged particle) from threshold to 20 MeV using NLD models

58Ni(n, p)58Co, 58Ni(n, 2p)57Fe, 58Ni(n, d)57Co, 58Ni(n, t)56Co and 58Ni(n, α)55Fe reactions are studied using different NLD models from threshold to 20 MeV. Five phenomenological and two microscopic NLD are employed using TALYS 1.9 and EMPIRE 3.2.2 nuclear reaction codes for theoretical calculations. Experimental data taken from EXFOR data library were compared with these. Statistical factors H, R and D have been used to identify the best fitted model. Level density parameters have also been adjusted for further fine-tuning with experimental data. CTFG model is appeared to be a good theoretical fabricator for the neutron-induced 58Ni reaction with newly adjusted level density parameters.

Nuclear level density of 69Zn from gamma gated particle spectrum and its implication on 68Zn(n, γ)69Zn capture cross section

Evaporated α-spectra have been measured in coincidence with low energy discrete γ-rays from residual nucleus 68Zn populated by αn evaporation from compound nucleus 73Ge produced in the reaction 64Ni(9Be,αn)68Zn at E(9Be) = 30 MeV. Low energy γ-gated α-particle spectra, for the first time, have been used to extract the nuclear level density (NLD) for the intermediate 69Zn nucleus in the excitation energy range of E ≈ 4-20 MeV. The slope of present NLD data as a function of excitation energy for 69Zn matches nicely with the slope determined from RIPL estimates for NLD at low energies and the NLD from neutron resonance data at neutron separation energy Sn. The extracted inverse NLD parameter (k = A/a˜) has been used to determine the nuclear level density parameter value a at neutron separation energy Sn for 69Zn. The cross section of 68Zn(n,γ) capture reaction as a function of neutron energy is then estimated employing the derived a(Sn) in the reaction code TALYS. It is found that the estimated neutron capture cross section agrees well with the available experimental data without any normalization. The present result indicates that experimentally derived nuclear level density parameter can constrain the statistical model description of astrophysical capture cross section and optimize the uncertainties associated with astrophysical reaction rate.

Nuclear Level Density and the Structural Dynamics of Rotating Superheavy Nucleus Z = 117

The temperature dependence of the recently synthesized superheavy nucleus Z = 117 is extensively studied through the statistical model for a wide range of isotopes. The model code is developed and executed for calculating the excitation energy, single neutron separation energy, level density, and entropy for the hot system. The possible sub-magic and magic numbers predicted are 178, 184, and 196. It is found that the pairing correlation collapses at T = 0.8 MeV and shell effect vanishes at T = 2.5 MeV. The limiting temperature is determined from the behavior of the level density parameter as a function of temperature.

Systematics of different quantities related to sequential prompt emission in fission

A deterministic treatment of sequential neutron emission, based on recursive equations of the residual temperatures, was applied to numerous fission cases (i.e. 49 cases including nuclei fissioning spontaneously or induced by thermal and fast neutrons) for which reliable experimental data of fragment distributions exist. This fact emphasizes systematics and correlations between different average quantities characterizing the initial and residual fission fragments and the sequential prompt neutron emission. The ratios of the average residual temperature following the emission of each neutron to the average temperature of initial fragments ($${ }/{ }$$) are almost constant for all studied fission cases. They do not depend on the prescriptions used for the compound nucleus cross-sections of the inverse process and the level density parameters of initial and residual fragments. This finding allows the determination of a general form of the residual temperature distribution for each emission sequence $${P}_{{k}}(T)$$ with the maximum temperature related only to the average temperature of initial fragments. In this way the sequential emission can be included into the Los Alamos model. Prompt neutron spectra in the center-of-mass and laboratory frames can be calculated for each emission sequence. The systematic of the ratios of average residual temperatures and energies to the initial ones together with other linear correlations between different prompt emission and residual quantities allow to obtain indicative values of different average prompt emission quantities in the absence of any prompt emission model.

Analysis of n-evaporation from light mass nuclei formed via p-induced reactions

This work deals with the decay analysis of three compound nuclei [Formula: see text], [Formula: see text] and [Formula: see text] formed in proton-induced reactions [Formula: see text], [Formula: see text] and [Formula: see text] at incident beam energies of 1–5 MeV using the Dynamical Cluster-decay Model (DCM). The motive is to explore the decay of compound systems formed via light charged particles as projectiles. The experimentally available data of n-evaporation for the aforementioned systems are addressed by optimizing the neck-length parameter [Formula: see text], using spherical fragmentation approach. The comparative analysis of the decay structure of the chosen systems is carried out at a common incident beam energy [Formula: see text] MeV. The effect of angular momentum [Formula: see text] and quadrupole [Formula: see text]-deformations is explored in reference to the decay structure/fragmentation of compound systems. In addition to this, the sensitivity of DCM-based cross-sections toward level density parameter (LDP) [Formula: see text] is also analyzed. The relative role of mass-dependent level density parameter [Formula: see text] is also investigated for compound systems belonging to light and heavy mass region. Lastly, a theoretical systematics is explored where the proton beam in the reaction [Formula: see text] is replaced by a neutron beam forming the compound system [Formula: see text], having the same [Formula: see text], but [Formula: see text] one less than that of the compound system formed in the reaction using proton beam, and its effect on the decay characteristics such as preformation probability, penetration probability and barrier height is analyzed.

Study of the 191Ir(n,2n)190Ir cross section

The 191Ir(n,2n)190Ir cross section was measured by using of the activation technique at four neutron energies in the range 10.0-11.3 MeV. The quasimonoenergetic neutron beam was produced via the 2H(d,n)3He reaction at the 5.5 MV Tandem Van de Graaff accelerator of NCSR ”Demokritos”. After the irradiations the induced activity of the samples was measured through a 56% relative efficiency HPGe detector. The cross section for the population of the second high spin (11−) isomeric state was measured along with the sum of the reaction cross section populating both the ground (4−) and the first isomeric state (1−). The experimental data will be combared to theoretical calculations in order to deduce information for the spin dependence of the level density parameters.