Measured Excitation Functions Research Articles

Production cross sections of radionuclides in the proton induced reactions on natural iron with the proton energy of 57 MeV

The production cross sections of 55,56,57Co, 52gFe, 52g,54Mn, 51Cr, and 48V from the natFe (p,x) reactions were measured using a proton energy of 57 MeV at the Korea Multi-purpose Accelerator Complex (KOMAC) in Gyeongju, Korea. The conventional stacked-foil activation method and offline γ-ray spectroscopy were used to determine the excitation functions of proton induced nuclear reactions on iron. The measured excitation functions were compared with experimental data in literature and theoretical data from the TENDL-2021 library. The present data show generally good agreement with other experimental data, but discrepancies were found between the present data and the excitation functions of the TENDL-2021 library in the investigated energy range, except for 56,57Co and 54Mn.

A Study of Complete and Incomplete Reactions of 12C + 169Tm System at Energy Range ≈ 4.16 –7.5 MeV/Nucleon

An attempt was made in this study to measure the excitation functions of 169Tm(12C, 4n)177Re, 169Tm(12C, 5n)176Re, 169Tm(12C, αn)176Ta, 169Tm(12C, α2n)175Ta, 169Tm(12C, α3n) 174Ta, 169Tm(12C, α4n)173Ta and 169Tm(12C, 2α2n)171Lu reaction channels populated in the interaction of 12C projectile with 169Tm target were considered in order to investigate the mechanisms of complete and incomplete fusion reactions. The theoretically predicted excitation functions using the PACE4 code were compared with the previously measured excitation functions. For non α emitting channels cross-section values predicted by PACE4 in general were found to be in good agreement with the experimentally measured values. However, for α-emitting channels, the measured cross-section values were found to be higher than the values predicted by PACE4. The observed disagreement may be credited to projectile break-up in the vicinity of n-n interaction.

Analysis of residual cross sections from N14+Nb93 reaction: Fusion dynamics of a non- α -cluster projectile

In the low-energy region, efforts have been made to understand the fusion mechanism of non-$\ensuremath{\alpha}$-cluster projectiles, such as $^{14}\mathrm{N}$ and $^{19}\mathrm{F}$. However, analyzing the contributing degrees of freedom has been hard in such reactions due to the lack of experimental data. This article reports the measurement of residual cross sections from the $^{14}\mathrm{N}$ induced reaction on $^{93}\mathrm{Nb}$ within the energy range of 42--59 MeV. The residues $^{104}\mathrm{Cd}$, $^{104}\mathrm{Ag}$, $^{103}\mathrm{Ag}$, $^{101}\mathrm{Pd}$, and $^{101m}\mathrm{Rh}$ produced during the reaction were identified using $\ensuremath{\gamma}$-ray spectroscopy. The measured excitation functions have been analyzed with the equilibrium and pre-equilibrium mechanism-based model codes to understand the associated reaction mechanism. A revision of intensity corresponding to the 118.72 keV $\ensuremath{\gamma}$ ray of $^{103}\mathrm{Ag}$ has also been proposed in this article.

Understanding the low-energy incomplete fusion reactions

With a motivation to find out the systematics for the low-energy ($\ensuremath{\approx}4$--7 MeV/nucleon) incomplete fusion reactions, the experimentally measured excitation functions for evaporation residues, which were populated during the interactions of $^{18}\mathrm{O}$ with $^{159}\mathrm{Tb}$ target nuclei, have been studied. The analysis clearly exhibits that the $xn/pxn$ channels are populated to a large extent through the complete fusion processes. Although, the production cross-section of the $\ensuremath{\alpha}$-emitting channels, despite of deducting the precursor decay contribution, found to be significantly under-estimated by the statistical model predictions. The observed enhancement, which may be attributed due to the involvement of break-up fusion processes, is found to be get larger with the incident energy. In addition, the present work in light of the literature data imparts the reliance of incomplete fusion processes on various entrance channel parameters, such as the mass-asymmetry of the interacting partners, fissility parameter and also on the ${Z}_{P}{Z}_{T}$ (Coulomb factor). These systematics inarguably indicates the projectile type dependency of the incomplete fusion reactions, and the results may be explained on the basis of the $\ensuremath{\alpha}\text{\ensuremath{-}}Q$ value of the projectile. Furthermore, an attempt has been made to explain the trends of incomplete fusion fractions through the total asymmetry parameter and the system parameter, where system parameter seems to explain the data more satisfactorily, as it incorporates the Coulomb factor as well as the masses of the interacting partners.

Consistent assessment of neutron-induced activation of 93Nb

A concurrent assessment of all measured excitation functions for various reactions induced by neutrons on 93Nb, in addition to the results of TENDL-2021 and default parameters in TALYS-1.96, is given in this work. We use consistent parameter sets that were formerly obtained or validated by the analysis of other independent data, while no empirical rescaling factors of γ and/or neutron widths have been used. The correlation between the measured error bars of the primary data providing the consistent input parameters and the final uncertainty bands of the calculated results have been pointed out. At the same time, a proper account in this work of all available data for competitive reaction channels prevented compensation effects of less accurate model parameters. Remaining questions and the need for additional measurements are emphasized.

Excitation function measurements of the elastic and inelastic scattering of protons in the 1600 to 5300 keV energy range for Li and F

Excitation function measurements of the elastic and inelastic scattering of protons in the 1600 to 5300 keV energy range for Li and F

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.

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.

Disentangling fractional momentum transfer in the F19+Sm154 system

Forward recoil range distributions of evaporation residues produced in the system $^{19}\mathrm{F}+^{154}\mathrm{Sm}$ were measured at projectile energy $\ensuremath{\approx}107$ MeV using the offline $\ensuremath{\gamma}$-ray activation technique. The entire and fractional linear momentum transfers inferred from these recoil range distributions were used to identify the evaporation residues formed by complete and incomplete fusion mechanisms. The forward recoil range distributions of measured evaporation residues populated through $x\mathrm{n}/\mathrm{p}x\mathrm{n}$ channels were found to be consisting of a single peak only while the evaporation residues populated through $\ensuremath{\alpha}$ emitting channel had contributions from incomplete fusion also. The observed incomplete fusion process in the population of $\ensuremath{\alpha}$ emitting channel residues is explained through the breakup fusion model. The results indicate the occurrence of incomplete fusion involving the breakup of $^{19}\mathrm{F}$ into $^{4}\mathrm{He}+^{15}\mathrm{N}$ and/or $^{8}\mathrm{Be}+^{11}\mathrm{B}$ followed by fusion of one of the fragments with target nucleus $^{154}\mathrm{Sm}$. From these measurements, the relative contributions of complete and incomplete fusion were separated out. The forward recoil range distributions data show that the incomplete fusion contribution in the fusion of fragment $^{15}\mathrm{N}$ is more dominant as compared to the fusion of fragment $^{11}\mathrm{B}$ with $^{154}\mathrm{Sm}$ target due to the smaller value of $\ensuremath{\alpha}$ breakup threshold energy $({E}_{\mathrm{B}.\mathrm{U}.}^{\ensuremath{\alpha}})$. The measured forward recoil range distributions of evaporation residues produced through $\ensuremath{\alpha}$ emitting channels provide experimental signature of strong clustering in $^{19}\mathrm{F}$ projectile as $\ensuremath{\alpha}$ and $^{15}\mathrm{N}$. The incomplete fusion strength function has also been deduced from the measured recoil range distributions and found to be compatible with those deduced from the measured excitation functions for the same system and beam energy.

Measurement of excitation functions for nat Cu(α, x) reactions with detailed covariance analysis

The excitation functions of 66Ga, 67Ga, 65Zn and 64Cu radioisotopes produced via alpha-induced reaction on nat Cu were measured using a stacked foil activation method. The gamma-ray activity produced by the above mentioned radionuclides was measured using the HPGe detector. The covariance analysis was performed to quantify the measured cross-section uncertainties as well as the correlation between different alpha energy cross-sections. A covariance matrix and cross-sections for the nat Cu(α, x)66Ga, nat Cu(α, x)67Ga, nat Cu(α, x)65Zn and nat Cu(α, x)64Cu nuclear reactions in the projectile energy range of 15–37 MeV are reported in the present work. The measured reaction cross-sections are compared with the existing experimental data and theoretically simulated results from the TALYS code.

A Study of Reaction Dynamics in the Interaction of 14N+59Co System at 32-56 MeV

The present work was done to investigate the reaction mechanisms involved in the interaction of 14 N projectile with 59 Co target at beam energies ∼32-56 MeV. The experimentally measured excitation functions available in the literature [2] were compared and analyzed with the statistical model code PACE4 calculation. For non-α emitting channels populated via complete fusion reaction, the measured excitation functions, after correcting them for possible contributions coming from higher charge isobaric precursor decays, were in general found to be in good agreement with theoretical predictions. However, for α-emitting channels, the experimentally measured excitation functions had more production cross-sections than what PACE4 predicted. The observed enhancement in the present case may be attributable to process of incomplete fusion from break-up of 14 N projectile. It may be pointed out that incomplete fusion reaction increases with increase in projectile energy. The observation of high incomplete fusion reaction is attributable to the prompt breakup of 14 N projectile into α-cluster. DOI: 10.7176/APTA/86-03 Publication date: October 31 st 2022

A Study of Excitation Functions in the Interaction of 4He + 59Co System at 4-9MeV/Nucleon

The excitation functions for six reactions produced in the interactions of 4He +59Co have been measured in the energy range up to 41MeV using the activation technique. The measured excitation functions are compared with theoretical calculations done using the computer program COMPLET. The effect of the variation of various program parameters on calculated excitation functions have been studied. The study signified that an admixture of equilibrium and pre-equilibrium emissions is required to reproduce the presently calculated excitation functions.An attempt was made to deduce the contribution coming from pre-equilibrium emission. It was found that the pre-equilibrium contribution increases with projectile energy. Further, the threshold of pre-equilibrium emission for different reaction channels is found to be different, depending on the associated Q-value. Furthermore, the present result revealed a strong correlation between pre-equilibrium contribution and particle multiplicity. DOI: 10.7176/APTA/86-01 Publication date: October 31 st 2022

Hints of quasi-molecular states in 13B via the study of 9Li-4He elastic scattering

This paper reports on elastic scattering excitation functions for the reaction 9Li+4He measured at backward angles in the centre of mass energy range 5 MeV ≤ E≤c.m.9.5 MeV, with the aim of investigating the possible existence of molecular resonances which have been predicted to exist in the case of neutron-rich B-isotopes. Due to the short lifetime of 9Li, the experiment necessitated the use of inverse kinematics on a gaseous 4He target. The Thick Target Inverse Kinematics technique was used which allowed for the measurement of the full excitation function in a single 9Li run. Broad resonances were observed in the excitation region for 13B 15 MeV ≤ Ex≤20 MeV. To understand the nature of such broad structures, various theoretical attempts are reported concerning possible reaction mechanisms for this neutron rich reaction. The most promising approach to interpret the data is within the orbiting reaction scenario.

Evaporation-residue cross sections in complete fusion reactions leading to Hg and Rn isotopes

The complete-fusion excitation functions of $xn$-evaporation channels for the reactions $^{144}\mathrm{Sm}(^{40}\mathrm{Ar},xn)^{184\ensuremath{-}x}\mathrm{Hg}$, $^{148}\mathrm{Sm}(^{36}\mathrm{Ar},xn)^{184\ensuremath{-}x}\mathrm{Hg}$, $^{144}\mathrm{Nd}(^{40}\mathrm{Ca},xn)^{184\ensuremath{-}x}\mathrm{Hg}$, $^{142}\mathrm{Nd}(^{48}\mathrm{Ca},xn)^{190\ensuremath{-}x}\mathrm{Hg}$, and $^{166}\mathrm{Er}(^{40}\mathrm{Ar},xn)^{206\ensuremath{-}x}\mathrm{Rn}$ have been measured by using the catcher foil technique. Its modified version as well as a corresponding software of data processing, including a deconvolution procedure to take into account effects caused by spreading the energy of the beam at its passing through absorbing foils, have been described. The measured excitation functions have been compared with ones theoretically calculated with the coupled-channel model.

Understanding the mechanisms of L-shell x-ray emission from Os atoms bombarded by 4–6 MeV/u fluorine ion

The L-subshell ionization mechanism is studied in an ultra-thin Os target bombarded by 4–6 MeV/u fluorine ions. Multiple ionization effects are considered through the change of fluorescence and Coster-Kronig yields while determining L-subshell ionization cross sections from L x-ray production cross sections. The present experimental values are compared with various theoretical approximations: (i) the relativistic semi-classical approximation (RSCA), (ii) the shellwise local plasma approximation (SLPA), and (iii) the ECUSAR theory. We also take into account the vacancy sharing among the subshells by the coupled-states model (CSM) and the electron capture (EC) by a standard formalism. We find that the ECUSAR-CSM-EC describes the measured excitation function curves the best. However, the theoretical calculations are still about a factor of two smaller than the measured values even though the recent fluorescence and Coster-Kronig yields are considered. Hence, a re-evaluation of these parameters is a challenge for the theoretical works. Whatsoever, this work leads to demonstrate that in the present energy range the heavy-ion induced inner-shell ionization of the heavy atoms can be understood by combining the direct Coulomb ionization, the electron capture, and the vacancy sharing among subshells, together with optimizing the atomic parameters. Optimization of the atomic parameters shows that our experimental results agree with theoretical vacancy production theories if the L1 fluorescence yield is nearly doubled. Such a optimization is validated by the proton induced L-shell ionization data of uranium atoms.

A Study of excitation functions in the interaction of α + 59Co system at 4~9MeV/Nucleon

In this work, α-induced 59Co reactions in the energy range from 11- 41MeV were used in order to study the role of pre-equilibrium emission. The experimentally measured excitation functions for residues populated via (α, n),(α, 2n),(α,3n),(α,2p),(α, 3n 2p) and (α, 4n 2p) channels in the interaction of + 59Co system available in the literature [13] were compared with theoretical predictions obtained using the statistical model code COMPLET. It was observed that at higher energy points the pure compound nucleus predictions, in general, failed to reproduce the measured data at projectile energies ~11-41MeV, this shows significant contributions from pre-equilibrium emission. The study signified both equilibrium and pre-equilibrium emissions were required to reproduce the presently measured excitation functions. An attempt was made to deduce the contribution coming from pre-equilibrium emission. It was found that the pre-equilibrium contribution increases with increasing projectile energy. Furthermore, the present result revealed a strong correlation between pre-equilibrium contribution and particle multiplicity.

Reaction dynamics of the C12+Ta181 system near the Coulomb barrier: Evidence of fusion-fission events

Background: Interaction of a heavy projectile with a heavy target produces a massive compound nucleus (CN), which deexcites through two possible modes: evaporation of light particles and fission. In order to develop a clear understanding of fusion-fission (FF) dynamics, it is important to explore the preactinide region at energies around and above the Coulomb barrier.Purpose: The objective is to study the dynamics involved in the fusion of $^{12}\mathrm{C}$, a cluster structured projectile, with $^{181}\mathrm{Ta}$ target, at energies within 4.3--6.0 MeV/nucleon, by measuring the production cross sections of the radionuclides formed through complete/incomplete fusion (CF/ICF) and fission processes. In addition, the mass distribution of fission fragments, which is an important fission observable, is probed for a better understanding of dynamics.Method: Tantalum foil, backed by the aluminum catcher, arranged in a stack, was bombarded by $^{12}\mathrm{C}$ ions of 52--73 MeV energy. The off-beam $\ensuremath{\gamma}$-ray spectrometry method was adopted to measure the activity of the residues produced in each Ta target after the end of bombardment (EOB), and cross sections were calculated. To analyze the experimental cross sections, PACE4 and EMPIRE3.2.2 reaction model codes were employed. Further, the mass distribution of fission fragments was explored to obtain mass variance information.Results: In general, measured excitation functions of the residues produced through the evaporation of particles in $^{12}\mathrm{C}+^{181}\mathrm{Ta}$ reaction showed good agreement with the predictions of PACE4. ICF of $^{12}\mathrm{C}$ in $^{181}\mathrm{Ta}$ target with strength up to $7.7%$ has been observed and compared with the strength deduced from previously reported data for the same system. However, no signature of precompound processes has been observed in this study. A total of 12 fission fragments within $71\ensuremath{\le}A\ensuremath{\le}135$ mass range have been identified. Further, mass variance is rising with increasing mass asymmetry, which hints at the importance of entrance-channel parameters' role in deciding the spread of the mass distribution.Conclusions: Good agreement of PACE4 with the excitation functions of $xn$ channel evaporation residues confirms their production through the CF mechanism. Enhancement of cross sections in the $\ensuremath{\alpha}xn$ channel is attributed to the ICF process. Further, evidence of the production of fission fragments through a compound nuclear mechanism is indicated as a broad and symmetric mass distribution, observed through the Gaussian fitting. The trend of mass variance with rising excitation energy and mass asymmetry is found to be growing.

Exploring various features of the reaction mechanism involved in the collision of Li7 on Cu

Nuclear reaction induced by a weakly bound projectile on light-medium mass targets poses open questions on the fusion mechanism. It is seen that fusion suppression in such reactions is negligible, but that stands on the basis of scarcely available experimental data. Thus more experimental data are demanded to bring out a clear understanding. In the course of this, for the first time, a measurement of residual cross sections from $^{7}\mathrm{Li}$ induced reaction on $^{\mathrm{nat}}\mathrm{Cu}$ has been presented in this article within the 2.3--6.0 MeV/nucleon energy range. The residues $^{69,67,66}\mathrm{Ge}$, $^{68,67,66,65}\mathrm{Ga}$, and $^{69m,65,63}\mathrm{Zn}$ produced in the reaction have been identified by $\ensuremath{\gamma}$-ray spectroscopy. The measured excitation function of the residues has been analyzed using equilibrium and preequilibrium reaction models in the framework of empire-3.2.2 to understand the reaction mechanisms involved in the low energy region. The underlying reaction mechanism is shown to be a blend of equilibrium and preequilibrium processes. The intensity of the $\ensuremath{\gamma}$ peak 93.31 keV arising in the decay of $^{67}\mathrm{Ga}$ has been revised experimentally. The experimental intensity turns out to be about half the value reported in different nuclear databases. Fusion cross sections have been estimated using the experimental data and empire-3.2.2 code. The estimated fusion cross sections are in line with coupled channel calculations taking inelastic excitations into account. The large production cross section of medically important $^{67}\mathrm{Ga}$ has been measured.

Impact of shell structure on the fusion of neutron-rich mid-mass nuclei

The influence of shell effects on fusion of mid-mass nuclei is explored using isotopic chains of K and Ar ions on an oxygen target. Comparison of the reduced excitation functions reveals that the fusion cross section for the open neutron-shell projectile nuclei $^{41}\mathrm{K}$ and $^{45}\mathrm{K}$ is systematically larger than for the closed neutron-shell projectiles $^{39}\mathrm{K}$ and $^{47}\mathrm{K}$. The S\~ao Paulo fusion model using matter densities from systematics fails to describe the measured excitation functions. Use of more realistic densities from a Dirac-Hartree-Bogoliubov (DHB) approach performs significantly better though it still overpredicts the closed-shell nuclei.

Effect of non- α -cluster projectile on incomplete-fusion dynamics: Experimental study of the N14+Ta181 system

In order to study incomplete fusion (ICF) reaction dynamics, the present work manifests the role of a non-$\ensuremath{\alpha}$-cluster $^{14}\mathrm{N}$ projectile on $^{181}\mathrm{Ta}$ target at energies $\ensuremath{\approx}4--7$ MeV/nucleon using the offline $\ensuremath{\gamma}$-ray spectroscopy. The excitation functions for 15 reaction residues populated in $^{14}\mathrm{N}+^{181}\mathrm{Ta}$ system have been measured and analyzed within the framework of statistical model code PACE4. The experimentally measured excitation functions of evaporation residues populated via xn/pxn channels are found to be well reproduced by the predictions of code PACE4, which confirms their production solely via complete fusion process. However, an enhancement in the measured excitation function as compared to PACE4 calculations, particularly in tail portion of $^{192}\mathrm{Hg}$ residue ($3n$ channel) has been observed indicating the presence of precompound emission. A significant contribution from precursor decay in pxn channels has also been observed. An enhancement in the measured excitation functions for $\ensuremath{\alpha}$-emitting channels as compared to the PACE4 predictions has been observed and attributed to the incomplete fusion process. Further, the contribution from incomplete fusion process in the $^{14}\mathrm{N}+^{181}\mathrm{Ta}$ system has also been deduced in terms of strength function (${F}_{\mathrm{ICF}}$). The results have been discussed in terms of the parameters which influence the dynamics of ICF process. The ${F}_{\mathrm{ICF}}$ is found to depend strongly on projectile energies, the product of projectile and target charges, and $\ensuremath{\alpha}\ensuremath{-}Q$ value of the projectile.