Isomeric Cross-section Ratios Research Articles

Evaluation of 180mTa formation cross-sections in photoneutron reactions

Determining the relative production cross-sections of the short-lived (ground) and long- lived (metastable) states of 180Ta is integral in nuclear physics research. However, direct measurement of these cross-sections is challenging. In this study, we proposed a method for estimating the total flux-weighted average formation cross-section of 180m+gTa based on GEANT4 modeling to evaluate the short-lived (ground) and long-lived (metastable) states of 180Ta. A Ta target was irradiated by a bremsstrahlung photon beam (maximum electron energy: 20 MeV) obtained from the linear electron accelerator LUE-75 at the A.I. Alikhanyan National Science Laboratory (AANL), Armenia. The experiment was performed using the activation technique, and the proposed GEANT4 simulation-based method was employed to evaluate the flux-weighted average formation cross-section of 180mTa. In addition, the isomeric cross-section ratio for the 180m,gTa isomeric pair was calculated. The theoretical results obtained using the TALYS 1.96 and EMPIRE 3.2 codes were consistent with the experimental ones. To the best of the authors’ knowledge, this paper reports the estimated flux-weighted average formation cross-section of 180mTa and isomer ratio for the 180m,gTa isomeric pair, induced by the irradiation of a bremsstrahlung beam with an end-point energy of 20 MeV, for the first time. This study opens new avenues for determining the relative production cross-sections of the ground and metastable states of 180Ta, which is widely studied as a natural isomeric target in various fields, including nuclear transformation reactions, fission dynamics, etc.

Investigation of the fusion mechanism in the Li6 -induced reaction on Nb93

We attempt to put forth the competing reaction mechanisms through residual cross section measurement in $^{6}\mathrm{Li}$ fusion with $^{93}\mathrm{Nb}$. The measured residual cross sections in the 24--43 MeV energy range are analyzed with the theoretical estimations from pace4, empire3.2.2, and alice23 statistical model codes. The replication of major $xn$-channel cross sections by empire with enhanced generalized superfluid model (EGSM) level density confirms that the population of $xn$-channel residues is through the complete fusion (CF) mechanism. The preequilibrium (PEQ) emission signatures were witnessed in the case of $^{97}\mathrm{Ru}$ residue populated via the $2n$ channel. Amplification of major experimental $p$- and $\ensuremath{\alpha}$-channel cross sections relative to the optimal theory was interpreted by considering the possibility of an incomplete fusion (ICF) process in addition to CF, owing to the low breakup threshold of the $^{6}\mathrm{Li}$ projectile. Thus, the ICF strength fraction $({F}_{\mathrm{ICF}})$ was estimated. The ${F}_{\mathrm{ICF}}$ turned out to be $\ensuremath{\approx}8--20%$ with an increasing trend and is found to be thoroughly higher than the deduced ${F}_{\mathrm{ICF}}$ for $^{7}\mathrm{Li}$ reaction on $^{93}\mathrm{Nb}$ target. In the case of weakly bound $^{6,7}\mathrm{Li}$-induced reactions, the first attempt is made to understand the influence of entrance channel parameters such as bombarding energy, $\ensuremath{\alpha}$-separation energy, Coulomb factor, mass asymmetry, neutron skin thickness, angular momentum, etc., on ${F}_{\mathrm{ICF}}$. The observed trend of the isomeric cross section ratios from the relative population of isomeric and ground states of $^{96,94}\mathrm{Tc}$ radionuclides is also discussed.

Facets of reaction mechanism in 6Li+181Ta system

More focused investigations are required to better understand the different modes of fusion phenomena in weakly bound projectiles. In order to comprehend the reaction mechanism of weakly bound projectiles, a new measurement of the evaporation residue cross sections from the 6Li-induced reaction on 181Ta in the 4.5–7.1 MeV/nucleon energy range has been reported in this article. The γ-ray spectrometry has been employed to identify the 183m,g Os, 182Os, 183Re, and 183,182m2,180Ta residues produced in the reaction via different evaporation channels. The EMPIRE-3.2.2 code, which houses both the equilibrium and pre-equilibrium models in its framework, and PACE4 have been tasked to analyze the measured excitation functions. Out of the two, EMPIRE-3.2.2 demonstrates better agreement with the data. A systematic analysis of the measured data and theoretical background indicates that the complete and incomplete fusion of 6Li contribute to the residual cross sections. Thus, the strength of the partial fusion has been inferred. Further, the neutron transfer channels have been found to contribute significantly to the reaction dynamics; hence they are investigated using the coupled reaction channel calculations and discussed in detail. The isomeric cross section ratio obtained from the measured residual cross sections of the isomeric pair of 183Os highlights the significance of angular momentum and relative spins of the ground and isomeric states as a function of projectile incident energy.

Cross-section measurements of the 81Br(n,2n)80mBr reaction via secondary nuclear decay

The secondary nuclear decay method was applied for the cross-section measurement of the 81Br(n,2n)80mBr reaction. As a result, the cross-sections of the 81Br(n,2n)80m,gBr reactions with a detailed uncertainty propagation and their isomeric cross-section ratios σm/σg were obtained at four neutron energies within the range from 13 to 15 MeV by applying an activation and off-line γ-ray spectrometric technique. The Br-based samples and Nb-based monitor foils were activated together to determine both the reaction cross-sections and the incident neutron flux. The neutron beam was formed via the 3H(d,n)4He reaction. The cross-sections were also calculated by using a theoretical nuclear model code TALYS-1.95 with different options of level density at neutron energies varying from the reaction threshold to 20 MeV. The extracted results were analytically discussed and compared with the corresponding theoretical and evaluated data from the published works in the literature.

Measurement and calculation of isomeric cross section ratios for the natW(3He, x)184m,gRe reactions

Excitation functions for the natW(3He, x)184m,gRe nuclear reactions were measured from respective thresholds up to 55 MeV by using a conventional stacked-foil activation technique combined with HPGe γ-ray spectroscopy. Individual cross-section values for the production of 184mRe and 184gRe were separated using a proper mathematical method based on their interference-free characteristic gamma lines and the data are reported here for the first time. The default parameters of recently developed nuclear model code TALYS-1.96 were found to be unable to reproduce the excitation functions, hence cannot provide 184mRe/184gRe isomeric cross-section ratios consistent with the experimental results. However, the adjustment of the level density model and optical model potentials together with some other parameters, such as the spin cut-off parameter, were found to be effective to reproduce the measured excitation functions. A similar parameter adjustment may be useful to reproduce the excitation functions of like unusual isomeric pairs, especially when the metastable state is longer-lived than the ground state.The reported cross-sections and the model calculation show interesting in the understanding of the nuclear reaction mechanisms as well as for the improvement of nuclear model codes for accurate prediction of nuclear reaction cross-sections where the experimental data are scarce, or an expensive experiment is required to obtain experimental data.

Excitation functions of proton-induced nuclear reactions on ^{86}Sr, with particular emphasis on the formation of isomeric states in ^{86}Y and ^{85}Y

Cross sections of proton-induced nuclear reactions on enriched ^{mathrm {86}}Sr target were measured by the activation technique up to proton energies of 44 MeV. The isomeric cross-section ratios for ^{mathrm {86m,g}}Y and ^{mathrm {85m,g}}Y as a function of projectile energy were deduced from their measured data. The present experimental data for the nuclear reaction products, namely ^{mathrm {86m}}Y, ^{mathrm {86g+xm}}Y, ^{mathrm {85m}}Y, ^{mathrm {85g}}Y, ^{mathrm {84}}Rb and ^{mathrm {83}}Rb were compared with the results of nuclear model calculations using the code TALYS, which combines the statistical, precompound, and direct interactions. In general, the experimental cross-section data as well as the isomeric cross-section ratios are reproduced well by the model calculations, provided the input model parameters are properly chosen and the level structure of the product nucleus is thoughtfully considered. The quality of the agreement between experimental data and model calculations was numerically quantified. For products formed via emission of a light complex particle as well as multi-nucleons (e.g., alpha and 2p2n), the contribution of the latter process starts increasing when its energy threshold is crossed.

Systematic study of the (n, 2n) reaction cross section for 121Sb and 123Sb isotopes

The cross sections of the 121Sb 120Sbm and 123Sb 122Sb reactions were measured at 12.50, 15.79 and 18.87 MeV neutron energies relative to the standard 27Al 24Na monitor reaction using neutron activation and offline γ-ray spectrometry. Irradiation of the samples was performed at the BARC-TIFR Pelletron Linac Facility, Mumbai, India. The quasi-monoenergetic neutrons were generated via the 7Li reaction. Statistical model calculations were performed by nuclear reaction codes TALYS (ver. 1.9) and EMPIRE (ver. 3.2.2) using various input parameters and nuclear level density models. The cross sections of the ground and the isomeric state as well as the isomeric cross section ratio were studied theoretically from reaction threshold to 26 MeV energies. The effect of pre-equilibrium emission is also discussed in detail using different theoretical models. The present measured cross sections were discussed and compared with the reported experimental data and evaluation data of the JEFF-3.3, ENDF/B-VIII.0, JENDL/AD-2017 and TENDL-2019 libraries. A detailed analysis of the uncertainties in the measured cross section data was performed using the covariance analysis method. Furthermore, a systematic study of the reaction cross section for 121Sb and 123Sb isotopes was also performed within 14–15 MeV neutron energies using various systematic formulae. This work helps to overcome discrepancies in Sb data and illustrate a better understanding of pre-equilibrium emission in the reaction channel.

Measurement of average cross sections and isomer ratios for natRe(γ,xn) reactions at the end-point bremsstrahlung energies of 30 MeV and 40 MeV

The cross sections for the natRe(γ,xn) reactions at the bremsstrahlung end-point energies of 30 MeV and 40 MeV have been measured by the activation and the off-line γ-ray spectrometric techniques using a High Purity Germanium (HPGe) detector. The measured natRe(γ,xn) reaction cross sections were compared to the theoretically calculated cross sections using TALYS 1.9 and EMPIRE 3.2 computer codes. The measurements allowed the determination of the Isomeric Cross section Ratios (ICR) for the 182m,gRe and 184m,gRe isomeric pairs. In addition, we have determined a semi-empirical ICR value for the 186m,gRe isomeric pair. These results for the bremsstrahlung end-point energies of 30 MeV and 40 MeV are obtained for the first time.

The formation of isomeric pair in the natTi(3He,x)44m,gSc reactions: Effect of spin cut-off parameter on the isomeric ratio

Excitation functions for thenatTi(3He, x)44g,mSc nuclear reactions were measured from respective threshold up to 55 MeV by using a conventional stacked-foil activation technique combined with HPGe γ-ray spectroscopy. Individual cross-section values for the production of44mSc and44gSc were separated using a proper mathematical method on the basis of their individual gamma lines and the data for44gSc are reported here for the first time. The default parameters of TALYS-1.8 are unable to provide the 44mSc/44gSc isomeric cross-section ratio values consistent with those obtained experimentally. However, an adjustment of the level density model and optical model potentials together with some other relevant parameters, especially the spin cut-off parameter with the variation ofη (=Ieff/Irigid) were found to be effective to reproduce the measured cross-sections. A similar parameter adjustment could be useful for accurate prediction of other medium mass isomeric pairs (i.e., when the metastable state is longer-lived than the ground state) where either experimental data are not available, or an expensive experiment is required to obtain them.

Fusion-fission events in the B11+Ta181 reaction up to 5.7 MeV/nucleon energy

Background: In heavy-ion fusion reactions, the compound nucleus' de-excitation process is observed via two competitive modes, evaporation of particles and fission, at relatively higher excitation energies. Although fusion-fission dynamics have been extensively studied in actinide nuclei, exploration of the same is yet to come for preactinide nuclei.Purpose: The objective is to understand the fusion-fission dynamics involved in the $^{11}\mathrm{B}+^{181}\mathrm{Ta}$ reaction within 4.8--5.7 MeV/nucleon energy by measuring absolute cross sections of the residues, which are mainly populating through complete and incomplete fusion-evaporation (FE), pre-equilibrium (PEQ), and fusion-fission (FF) mechanisms, as well as to infer on the mass and charge distributions of fission fragments.Method: The stacked-foil activation technique was employed, followed by off-line $\ensuremath{\gamma}$-ray spectroscopy, to measure the activity and production cross sections of radionuclides populated through FE and FF. Charge and mass distributions were studied to obtain dispersion parameters of fission fragments.Results: The equilibrium and pre-equilibrium reaction models have been used to analyze residual cross-section data resulting from FE and PEQ processes in the framework of EMPIRE3.2.2 and PACE4 codes. PEQ reaction's strengths in $3n$-channel have been extracted and compared with other systems. The relative distribution of spins between the ground and isomeric state of $^{186}\mathrm{Ir}$ has been discussed in view of the measured isomeric cross-section ratios. Further, 22 fission-fragments have been identified within the mass range $24\ensuremath{\le}A\ensuremath{\le}160$. The variance extracted from the measured isotopic yield distributions of Nd isotopes is in good agreement with the literature values. A well-consistent approach has been employed to determine the isobaric yield distribution of Nd and In isotopes.Conclusion: The combination of Hauser-Feshbach formalism for compound evaporation and the Exciton model for PEQ reaction agrees with the measured data of $xn$-channel residues, which confirms their production from the CF mechanism. Indirect evidence of ICF was observed in the $\ensuremath{\alpha}$- and $p$-emitting channels. Further, fission fragments' mass distribution is broad and symmetric, indicating their production through the compound nuclear mechanism. The variance of fission fragments' mass distribution shows an increasing trend with raising excitation energy.

New experimental data on excitation functions of He3 -induced nuclear reactions on Ta up to 27 MeV

Excitation functions of $^{3}\mathrm{He}$-induced nuclear reactions on $^{\mathrm{nat}}\mathrm{Ta}$ were measured utilizing the MGC-20E cyclotron, stacked-foils activation technique, and high-resolution gamma-ray spectrometry. From their threshold energies up to 27 MeV, cross sections for $^{\mathrm{nat}}\mathrm{Ta}(^{3}\mathrm{He},xn)^{182}\mathrm{Re}^{\mathrm{m}}, ^{182}\mathrm{Re}^{\mathrm{g}}, ^{181}\mathrm{Re}$, and $^{\mathrm{nat}}\mathrm{Ta}(^{3}\mathrm{He},\ensuremath{\alpha}xn)^{178}\mathrm{Ta}^{\mathrm{A}}, ^{180}\mathrm{Ta}^{\mathrm{g}}$ reactions were measured. The half-life of the radionuclide $^{181}\mathrm{Re}$ was checked experimentally. The intensity of the energy line 360.7 keV, in the radionuclide $^{181}\mathrm{Re}$ decay scheme, was revised experimentally. The new experimental intensity represents about half the reported value in the different nuclear structure databases. The nuclear reaction codes TALYS-1.9 and EMPIRE-3.2.3 were used to predict the formation of these products. The isomeric cross-section ratio for the $^{182}\mathrm{Re}^{\mathrm{m},\mathrm{g}}$ was also calculated. The ratio indicates that the pre-equilibrium mechanism is dominant at energies over 19 MeV. Various combinations of the models' parameters implemented in EMPIRE such as nuclear level density models, optical model, and pre-equilibrium parameters were used to reproduce the experimental excitation functions. For TALYS calculations, the TENDL-2019 nuclear data library based on TALYS-1.9 was used. The present data were compared to theoretical results and the available experimental data. Integral yields for the produced radioisotopes were determined.

Isomeric cross section ratios data as a test for codes descriptive of nuclear reactions

Investigations of isomeric cross-section ratios of the reactions 187Re(a,n)190mgIr, 194Pt(a,n)197mgHg and 41K(a,n)44mgSc in the energy range 18 – 32 MeV are carried out using off-beam measurements of induced activity of members of the isomeric pair. Analysis of the obtained ICSR data is performed using the codes EMPIRE-3 and TALYS. The reliability of these advanced data-containing codes is analyzed. The results of the measurements of the isomeric cross section ratios are proved to be a promising test of the codes and their capability to reproduce angular momentum dynamics of the discussed and related reactions.

Analysis of the dynamics of Li7 -induced fusion with natZr up to 44 MeV

An experimental study on the fusion dynamics of the $^{7}\mathrm{Li}+^{\text{nat}}\mathrm{Zr}$ reaction has been carried out within the 4.0 to 6.3 MeV/nucleon energy range by measuring cross sections of the populated residues with the help of $\ensuremath{\gamma}$-ray spectrometry. The equilibrium and pre-equilibrium reaction models have been used in the framework of empire3.2.2 to analyze the measured residual cross sections to shed light on the reaction mechanism involved in it. It indicates that the complete and incomplete fusion of $^{7}\mathrm{Li}$ contribute to the residual cross sections. Thus, the strength of incomplete fusion has been derived and is compared with other $^{7}\mathrm{Li}$-induced reactions in the similar mass range. Further, coupled channel (CC) calculations have been carried out to understand the effect of couplings in the fusion process. It has been observed that the fusion cross section is suppressed in $^{7}\mathrm{Li}+^{\text{nat}}\mathrm{Zr}$ reaction as compared to CC calculations far above the Coulomb barrier. The isomeric cross-section ratio has also been obtained from the measured cross sections of the isomeric pairs of $^{93,95}\mathrm{Tc}$ that describes the role of angular momentum and relative spins of the ground and isomeric states with the variation of bombarding energy.

Systematic study on some isotopes of medical and industrial applications, produced in proton induced reaction on natural cadmium

The excitation function for the proton induced nuclear reactions on natural cadmium was measured up to 23 MeV employing stacked foil activation technique using the 14UD pelletron accelerator. Experimental cross-section and isomeric cross-section ratio have been measured for the $$^{\mathrm{nat}}$$Cd(p,x) $$^{105,111\mathrm{m}}$$Cd, $$^{\mathrm{nat}}$$Cd(p,x) $$^{109\mathrm{g},110\mathrm{m},110\mathrm{g},111\mathrm{m},111\mathrm{g},112\mathrm{m}, 112\mathrm{g},113\mathrm{m},115\mathrm{m},116\mathrm{m}}$$In reactions. The excitation function of $$^{105}$$Cd and the isomeric cross-section ratio of $$^{110,111,112}$$In isotopes have been measured and reported for the first time. Theoretical analysis of the data are done using the statistical model codes EMPIRE-3.2 and TALYS-1.8. Various dependence of isomeric cross-section ratio on different factors such as the spin, life time of the isomeric states and also the dependence of the exit channel are well explained.

Activation cross-section and isomeric cross-section ratio for the 122Te(n,2n)121m,gTe process

Measurements of the cross-section for the 122Te(n,2n)121mTe and 122Te(n,2n)121gTe reactions and their ratio within the energy range of 13 –5 MeV have been carried out using the method of activation and off-line γ-ray spectrometry. The fast-moving neutrons were produced via the 3H(d,n)4He reaction on a K-400 neutron generator. Natural high-purity Te powder was used as the target material. The value of pure ground-state cross-section σg was obtained. Theoretical excitation functions were also calculated by means of the nuclear-reaction codes TALYS-1.95 with six level densities, at neutron energies varying from the reaction threshold to 20 MeV. The results were also discussed and compared with some of the corresponding values found in the literature.

Influence of Reaction Channel on Isomer Ratio of 184m,gRe Isomeric Pair

The influence of a reaction channel on the isomeric cross-section ratio (ICR) of the production of 184m,gRe was investigated. The excitation functions for the 184m,gRe isomeric pair produced through the 184W(p,n), 186W(p,3n), 184W(d,2n), 186W(d,4n), 181Ta(α,n) and 185Re(γ,n) reactions were calculated by different models of the TALYS 1.9 and EMPIRE 3.2 codes. The ICR calculations for the above-mentioned isomeric pair through the various reaction channels (proton, deuteron, alpha and gamma induced reactions) was determined for incident energy ranges from the threshold up to 50 MeV. The comparison of theoretical calculations and available experimental data was done.

New measurement of residues from Li7+Tanat reaction within 4–6.5 MeV/nucleon: Production yield for Os183

Exploration of reaction dynamics of the weakly bound heavy-ion interaction with an intermediate or heavy mass target in the low energy range has been a subject of interest over the past decades; however, different modes of fusion such as breakup fusion, incomplete fusion, and transfer phenomena observed experimentally are not yet fully understood. Experimental studies are therefore essential to address the problem. In this article, we report a new set of cross-section data of the residues produced in the weakly bound $^{7}\mathrm{Li}$ induced reaction on $^{\mathrm{nat}}\mathrm{Ta}$ within the 27--45 MeV energy range. Along with the major yield of $^{\text{183g+m}}\mathrm{Os}$, production of $^{\text{180m}}\mathrm{Hf}$ and $^{183}\mathrm{Ta}$ are also observed up to $\ensuremath{\sim}35\phantom{\rule{0.28em}{0ex}}\mathrm{MeV}$, which is possibly an indication of the incomplete fusion mechanism or breakup-transfer phenomena. The trend of the isomeric cross-section ratio of $^{183}\mathrm{Os}$ indicates the role of angular momentum and spin distribution besides the excitation energy, and is interpreted by theory. The optimized production parameters and yields of $^{\text{183g,m}}\mathrm{Os}$ are assessed.

Activation cross-sections for the 185Re(n, 2n) reaction and the isomeric cross-section ratio of 184m,gRe in the neutron energy range of 13\u201315 MeV

.Cross-sections and their isomeric ratios ( sigma_{mathrm{m}}/sigma_{mathrm{g}}) for the 185Re(n, 2n)184mRe and 185Re(n, 2n)184gRe reactions in the 13–15 MeV range were measured. The neutron activation technique was applied using the K-400 neutron generator at the Chinese Academy of Engineering Physics (CAEP). Natural Re samples and Nb monitor foils were activated jointly to determine the reaction cross-section and the incident neutron flux. The 3H(d, n)4He reaction was used to generate the neutron beam. The pure cross-section of the ground state was derived from the absolute cross-section of the metastable state using residual nuclear decay analysis. Numerical calculations using the nuclear-model-based computer code TALYS-1.8 with six level density models were used to obtain 185Re(n, 2n)184m, gRe reaction excitation functions and their isomeric cross-section ratios. Finally, experimentally determined cross-sections were compared with corresponding literature data.

Measurement of cross sections and isomeric cross-section ratios for the(n,2n)reactions onHg196,198at energies between 13 and 15 MeV

Measurement of cross sections and isomeric cross-section ratios for the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:mi>n</mml:mi><mml:mo>,</mml:mo><mml:mn>2</mml:mn><mml:mi>n</mml:mi></mml:mrow><mml:mo>)</mml:mo></mml:mrow></mml:math>reactions on<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Hg</mml:mi><mml:mprescripts /><mml:none /><mml:mrow><mml:mn>196</mml:mn><mml:mo>,</mml:mo><mml:mn>198</mml:mn></mml:mrow></mml:mmultiscripts></mml:math>at energies between 13 and 15 MeV

Isomer ratios and cross sections for the isomeric pair 122mSb and 122gSb in the 123Sb(n,2n) reaction

Cross-sections and their isomeric ratios σm/σg in the energy range of 13–15 MeV for isomeric pair 122mSb and 122gSb produced by the 123Sb(n,2n) reaction have been measured by activation and off-line γ-ray spectrometric technique using the K-400 Neutron Generator at the Chinese Academy of Engineering Physics (CAEP). Specifically, the versatile stacked foil irradiation technique and a high resolution HPGe detector were employed. The 3H(d,n)4He reaction was used to produce the neutron beam. Partial cross sections σm and σg were derived from the absolute cross section of the metastable state and residual nuclear decay analysis. The 123Sb(n,2 n)122m,gSb reaction excitation functions and their isomeric cross section ratios were numerically calculated with TALYS-1.8 code with different level density options. Results are discussed and compared with corresponding literature data.