Optical Model Potential Parameters Research Articles

Measurement of proton induced absolute production cross-section of 6.13, 6.92 and 7.12 MeV γ-rays from 16O(p,p ′γ )16O reaction

In this article, we report the absolute production cross-section of 6.13, 6.92 and 7.12 MeV γ-rays from the 16O(p,p ′γ )16O reaction for incident proton energy range of 8-16 MeV. Angular distributions of the three γ-rays have been measured for seven angles at 9 MeV proton energy. A detailed phenomenological optical model potential (OMP) was set up to analyse the cross-section data. The OMP parameters were optimised using elastic, polarization and total reaction data available in the literature for protons and neutrons. Low-lying states of 16O were coupled, the optical potential was deformed using deformation parameters, and several resonances were included in the calculations to account for the nuclear structure effects. The potentials so generated have been used to calculate the differential and total cross sections for both 16O(p,p ′ )16O and 16O(p,p ′γ )16O reactions. Our calculated cross-sections are in fairly good agreement with our measured data for 6.13, 6.92 and 7.12 MeV γ-rays. However, there still exist discrepancies in reproduction of the finer details of the cross sections. The comparisons of the calculations with the data bring forth the rather complex roles of channel couplings, resonances in the p+16O system and target deformation in the variation of the cross sections with projectile energy. The increased contribution of nuclear structure effects in light mass nuclei, leads to an apparent loss of predictive power of the theoretical calculation, as we approach the low-energy region of less than 10 MeV projectile energy.

γ-ray emission in proton-induced nuclear reactions on [formula omitted]C and Mylar targets over the incident energy range, Ep = 30 – 200 MeV. Astrophysical implications

We have measured the γ-ray line production cross sections in proton-induced nuclear reactions on various target nuclei (12C, 16O, 24Mg, 28Si, 56Fe) of chemical elements abundant in astrophysical sites (solar flares, the interstellar medium, cosmic compact objects) over the incident energy range of Ep = 30 – 200 MeV. We carried out experimental campaigns in joint collaboration at the K = 200 separated sector cyclotron of iThemba LABS using a high-energy resolution, high-efficiency detection array composed of 8 Compton-suppressed clover detectors comprising 32 HP-Ge crystals for recording the γ-ray energy spectra. In the current paper, we focus on γ-ray de-excitation lines produced in proton irradiations of natC and Mylar targets, in particular, on the prominent 4.439 and 6.129 MeV lines of 12C and 16O which are among the strongest lines emitted in solar flares and in interactions of low-energy cosmic rays (LECRs) with the gas and dust of the inner galaxy. We report new γ-ray production experimental cross section data for ten nuclear γ-ray lines that we compare to previous low-energy data sets from the literature, to the predictions of the TALYS code of nuclear reactions and to a semi-empirical compilation. In the first approach, performing calculations with default input parameters of TALYS we observed substantial deviations between the predicted cross sections and experimental data. Then, using modified optical model potential (OMP) and nuclear level deformation parameters as input data we generated theoretical excitation functions for the above two main lines fully consistent with experimental data. In contrast, the experimental data sets for the other eight analyzed lines from the two proton-irradiated targets exhibit significant deviations with the predicted cross section values. We also report line-shape experimental data for the line complex observed at Eγ = 4.44 MeV in irradiations of the two targets. Finally, we emphasize the astrophysical implications of our results.

Systematic investigation of channel-coupling effects on elastic, inelastic, and neutron-transfer channels in Li6+Tb159

Elastic scattering angular distribution for weakly bound nucleus $^{6}$Li on the deformed rare earth $^{159}$Tb target nucleus has been measured at energies around the Coulomb barrier. The elastic scattering cross sections for this reaction consist of inelastic contributions from low lying excited states of $^{159}$Tb. The pure elastic cross-sections have been extracted from the admixture of elastic and inelastic data. The optical model potential parameters for the system have been obtained from the extracted pure elastic scattering cross sections. Coupled channel calculations have been performed with this set of potential parameters, to compare the theoretical and experimental inelastic scattering cross sections. The work has been extended to obtain the spectroscopic factor for $^{158}$Tb+n configuration from the experimental 1n-pickup data.

Role of neutron transfer in the reaction mechanism of 9Be+169Tm, 181Ta, 187Re and 197Au systems

The contribution of one neutron stripping cross section to the total reaction cross section has been studied for 9Be projectile incident on 169Tm, 181Ta, 187Re and 197Au targets around Coulomb barrier energy. The measured one neutron stripping cross sections for these systems have been compared with the coupled channel calculations. The recently developed global set of optical model potential parameters for 9Be projectile has been used in the present calculations. The cumulative of measured complete fusion (CF), incomplete fusion (ICF), one neutron stripping and calculated non-capture breakup (NCBU) cross sections is found to explain almost the reaction cross sections for all the targets. A very small contribution from target inelastic states and elastic breakup may contribute to the remaining part. The percentage fraction of cross section for CF, ICF, one neutron stripping, and NCBU over reaction cross section show the dominance of neutron transfer and NCBU at below barrier energies while CF and ICF processes have the major contribution at above barrier energies.

Global phenomenological optical model potential for 14N-nucleus elastic scattering

In this paper, a set of global optical model potential parameters of [Formula: see text]N is obtained by fitting the experimental data of the elastic scattering angular distributions for the targets from [Formula: see text]Mg to [Formula: see text]Pb below 200 MeV. The global optical model potential parameters of [Formula: see text]N-nucleus reactions obtained are analyzed and used to describe the experimental data. It is found that the present form of the global optical model potential could reproduce the experimental data. Moreover, the elastic scattering angular distributions for the reactions of [Formula: see text]N inducing on some lighter targets and the elastic scattering observable quantity for the reactions involving [Formula: see text]N projectile are predicted using the obtained global optical model potential, and a reasonable description of the experimental data is obtained by comparing with the existing corresponding experimental data.

Mass-number dependence of statistical model parameters and its impact on incomplete fusion fraction calculations

Incomplete fusion processes and estimation of strength of incomplete fusion in heavy ion induced nuclear reactions have been explored for several combinations of projectile-target nuclei. Dynamics of these reactions is explained using an optical model. Parameters of the optical model affect the shape and depth of nuclear potential and hence influence the theoretical predictions. For heavy ion induced reactions, the optical model potential parameters are not unique and different sets of these parameters may be used for different ranges of mass number $A$ and incident energy $E$. To explore the effect of optical model potential parameters, a comparative study of available experimental data for excitation functions of four systems, $^{16}\mathrm{O}+^{181}\mathrm{Ta}, ^{12}\mathrm{C}+^{165}\mathrm{Ho}, ^{14}\mathrm{N}+^{163}\mathrm{Dy}$, and $^{16}\mathrm{O}+^{74}\mathrm{Ge}$, with corresponding theoretically predicted excitation functions, made by PACE4 using different sets of optical model potential parameters, has been done. It has been observed that a single set of optical model potential parameters is not adequate for all the systems. The variations in these parameters change the theoretical cross-section predictions for various channels considerably, which in turn, change the correspondingly estimated fraction of incomplete fusion $({F}_{\mathrm{ICF}})$. The effect of deformation of target nuclei on fractional incomplete fusion has also been investigated for the above mentioned systems. ${F}_{\mathrm{ICF}}$ has been plotted as a function of deformation parameter $({\ensuremath{\beta}}_{2})$ of the target nuclei and it is found to increase as the deformation parameter of the corresponding target nuclei increases on either side of the intrinsic spherical symmetry.

Model calculation of the differential cross sections and angle-integrated cross sections of the emitted triton for neutron-induced Li6 reactions at low incident energies

Regarded as important for applications and theoretical studies, the differential cross sections of the emitted triton for the neutron-induced $^{6}\mathrm{Li}$ reaction at low incident energies were calculated, based on the zero-range distorted-wave Born approximation theory with the assumption of $^{6}\mathrm{Li}$ nucleus consisting of $t{+}^{3}\mathrm{He}$ or $d+\ensuremath{\alpha}$. As a function of widths and excited energies of the discrete energy levels, an effective excited energy formula was proposed to describe their partial contributions. In addition, the optical model potential parameters, which had been successfully used to reproduce the double-differential cross sections of the emitted neutrons in our previous works in incident energy range from 5.0 to 20.0 MeV were extended in a low-energy range from 1.0 eV to 3.0 MeV in this paper. The calculated results agreed well with the measured differential cross sections recently published in 2020 and were further consistent with the measured angle-integrated cross sections. This indicates that the knock-out process and heavy-particle knockout process were dominant in an energy range from 1.0 eV to 3.0 MeV, whereas the shapes of the measured angular distributions in incident energy range from 0.1 to 1.0 MeV could be successfully explained by the Hauser-Feshbach model.

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.

Calculation and Evaluation for the n+51V Reaction

A set of optical model potential parameters for the n+51V reaction is obtained based on the experimental data of the total cross section, elastic scattering cross section, and elastic scattering angular distribution at incident energies up to 300 MeV. All cross sections, angular distributions, energy spectra, and double-differential cross sections for the n+51V reaction are consistently calculated and analyzed at incident neutron energies below 250 MeV. The theoretical nuclear models including the optical model, distorted wave Born approximation theory, Hauser-Feshbach theory, evaporation model, exciton model, and intranuclear cascade model are used in the analysis. The calculated results are compared with the experimental data and the evaluated results in ENDF/B-VII.1 and JENDL-4.

Global 6He optical model potential

A set of global [Formula: see text]He phenomenological optical model potential (OMP) parameters with incident energies up to 250[Formula: see text]MeV is obtained. They are based on a smooth, unique functional form for the energy dependence of the potential depths, and on physically constrained geometry parameters. The available experimental data including the reaction cross-sections and elastic scattering angular distributions from target [Formula: see text]Li to [Formula: see text]Bi are used. The global OMP parameters obtained for [Formula: see text]He are analyzed and used to calculate the reaction for [Formula: see text]He projectile. It is found that the present form of the global OMP can reproduce the experimental data for [Formula: see text]He and [Formula: see text]He projectiles.

Test of the notch technique for determining the radial sensitivity of the optical model potential**Supported by National Natural Science Foundation of China (11375268, 11475263, U1432246 and U1432127) and the National Key Basic Research Program of China (2013CB834404)

Detailed investigations on the notch technique are performed on ideal data generated by the optical model potential parameters extracted from the 16O+208Pb system at the laboratory energy of 129.5 MeV, to study the sensitivities of this technique to the model parameters as well as the experimental data. It is found that for the perturbation parameters, a sufficiently large reduced fraction and an appropriate small perturbation width are necessary to determine the accurate radial sensitivity; while for the potential parameters, almost no dependence was observed. For the experimental measurements, the number of data points has little influence for heavy target systems, and the relative inner information of the nuclear potential can be derived when the measurement is extended to a lower cross section.

Prediction of reaction cross section forp-Cr

Nuclear matter densities and charge radii for even 46−62 Cr isotopes have been calculated using relativistic Hartree-Bogoliubov model based on density-dependent meson-exchange relativistic energy density functional. The calculated root-mean-square charge radii agree well with corresponding data and the kink at N =28 is reproduced by the calculation. The calculated target matter densities are folded with the Jeukenne, Lejeune, and Mahaux-Bruyeres inter-nucleon interaction to obtain semi-microscopic optical model potentials for incident protons of 65 MeV on even 46−62 Cr isotopes. The elastic scattering differential cross sections calculated using the proton optical potentials reproduce corresponding data for stable isotopes. The optical model potential parameters required for prediction of differential and total reaction cross sections for unstable even isotopes have been obtained.

A Lane consistent optical model potential for nucleon scattering on actinide nuclei with extended coupling

An extension for odd-A actinides of a previously derived dispersive coupledchannel optical model potential (OMP) for 238 U and 232 Th nuclei is presented. It is used to fit simultaneously all the available experimental databases including neutron strength functions for nucleon scattering on 232 Th, 233,235,238 U and 239 Pu nuclei. Quasi-elastic (p,n) scattering data on 232 Th and 238 U to the isobaric analogue states of the target nucleus are also used to constrain the isovector part of the optical potential. For even-even (odd) actinides almost all low-lying collective levels below 1 MeV (0.5 MeV) of excitation energy are coupled. OMP parameters show a smooth energy dependence and energy independent geometry.

Global optical model potential for alpha projectile

A new set of global phenomenological optical model potential (OMP) parameters for alpha projectile is obtained by simultaneously fitting the experimental data of reaction cross-sections and elastic scattering angular distributions in the mass range of target nuclei [Formula: see text] at incident energies below 386[Formula: see text]MeV. The total reaction cross-sections and elastic scattering angular distributions are calculated and compared with experimental data for different targets. A satisfactory agreement is presented between them.

Optical Model Potential Using CINDA Library for Neutron Induced Cross Section Reactions for Spherical Uranium-235,238 Isotopes

The calculation are based mainly on the nuclear optical model potential and relevant parameters are collected and selected from References Input Parameter Library (RIPL) which is being developed under the international project coordinated by the International Atomic Energy Agency (IAEA). The analyzing of a complete energy range has done starting from threshold energy for each reaction. The cross sections are reproduced in fine steps of incident neutron energy with 0.01MeV intervals with their corresponding errors. The recommended cross sections for available experimental data taken from CINDA library have been calculated for all the considered neutron induced reactions for spherical U-235 and U-238 isotopes. The calculated results are analyzed and compared with the experimental data. The optimized optical potential model parameters give a very good agreement with the experimental data over the energy range 0.001-20MeV for neutron induced cross section reactions (n,f), (n,tot), (n,el), (n,inl), (n,2n), (n,3n), and (n,γ) for spherical U-235 and U-238 target elements.

Evaluation of Optical Model Potential Using Neutron Induced Cross Section Reaction for Spherical Uranium-238 Isotope up to 20MeV

The evaluation are based on mainly on the calculations of the nuclear optical model potential and relevant parameters are collected and selected from References Input Parameter Library (RIPL) which is being developed under the international project coordinated by the International Atomic Energy Agency (IAEA). The analyzing of a complete energy range has done starting from threshold energy for each reaction. The cross sections are reproduced in fine steps of incident neutron energy with 0.01MeV intervals with their corresponding errors. The recommended cross sections for available experimental data taken from EXFOR library have been calculated for all the considered neutron induced reactions for U-238 isotopes. The calculated results are analyzed and compared with the experimental data. The optimized optical potential model parameters give a very good agreement with the experimental data over the energy range 0.001-20MeV for neutron induced cross section reactions (n,f), (n,tot), (n,el), (n,inl), (n,2n), (n,3n), and (n,γ) for spherical U-238 target elements.

Optical Model Potential Using CINDA Library for Neutron Induced Cross Section Reactions for Spherical Uranium-235,238 Isotopes

The calculation are based mainly on the nuclear optical model potential and relevant parameters are collected and selected from References Input Parameter Library (RIPL) which is being developed under the international project coordinated by the International Atomic Energy Agency (IAEA). The analyzing of a complete energy range has done starting from threshold energy for each reaction. The cross sections are reproduced in fine steps of incident neutron energy with 0.01MeV intervals with their corresponding errors. The recommended cross sections for available experimental data taken from CINDA library have been calculated for all the considered neutron induced reactions for spherical U-235 and U-238 isotopes. The calculated results are analyzed and compared with the experimental data. The optimized optical potential model parameters give a very good agreement with the experimental data over the energy range 0.001-20MeV for neutron induced cross section reactions (n,f), (n,tot), (n,el), (n,inl), (n,2n), (n,3n), and (n,γ) for spherical U-235 and U-238 target elements.

Evaluation of Optical Model Potential Using Neutron Induced Cross Section Reaction for Spherical Uranium-238 Isotope up to 20MeV

The evaluation are based on mainly on the calculations of the nuclear optical model potential and relevant parameters are collected and selected from References Input Parameter Library (RIPL) which is being developed under the international project coordinated by the International Atomic Energy Agency (IAEA). The analyzing of a complete energy range has done starting from threshold energy for each reaction. The cross sections are reproduced in fine steps of incident neutron energy with 0.01MeV intervals with their corresponding errors. The recommended cross sections for available experimental data taken from EXFOR library have been calculated for all the considered neutron induced reactions for U-238 isotopes. The calculated results are analyzed and compared with the experimental data. The optimized optical potential model parameters give a very good agreement with the experimental data over the energy range 0.001-20MeV for neutron induced cross section reactions (n,f), (n,tot), (n,el), (n,inl), (n,2n), (n,3n), and (n,γ) for spherical U-238 target elements.

Experimental study ofAl26through the1npick-up reactionAl27(d,t)

The $^{27}\mathrm{Al}(d,t)$ reaction has been studied to extract spectroscopic information for the odd-odd nucleus $^{26}\mathrm{Al}$. The excited states of $^{26}\mathrm{Al}$ up to 5.50 MeV have been analyzed using the local, zero range distorted wave Born approximation. A new set of optical model potential parameters was extracted from the measured elastic scattering angular distribution. The spectroscopic factors calculated for these states are found to be in good agreement with previously reported values for the same; they are also in agreement with those obtained from shell model predictions.

Structure of26Al studied by one - nucleon transfer reaction27Al(d,t)

The excited states of 26 Al have been produced and studied using 27 Al(d,t) reaction with 25 MeV deuteron as projectile. Optical model potential parameters were extracted from the measured elastic scattering angular distribution. Zero range distorted wave Born approximation analysis for the ground and 0.223 MeV states of 26 Al have been done. The spectroscopic factors calculated for these states are found to be in good agreement with the previously reported values.