Initial Exciton Number Research Articles

Pre-equilibrium Effects on Alpha Particle Induced Reactions on Niobium Isotope from Threshold upto 100MeV using the Computer Code COMPLET

Excitation functions (EF) for four reactions of the type 93Nb (α, xn); x = 1-4 were studied. This study provides current evidences about the dominance of pre-equilibrium processes at high energies followed by compound nucleus equilibration at low energies. The main objective of the work is to look pre-equilibrium emission induced by alpha particle energies up to 100 MeV on Niobium through describing, analyzing and interpreting the theoretical results of cross sections obtained from computer code COMPLET by comparing with experimental data obtained from EXFOR library. COMPLET code has been used for the analysis using the initial exciton number n0 = 4(4p+oh) and level density parameter ACN/10. A general agreement was found for all reactions.

A new study on pre-equilibrium and equilibrium effects of excitation functions of alpha-induced reactions on 51V, 55Mn and 59Co nuclei

In this article, the cross section simulations of 51V(α,n)54Mn, 55Mn(α,n)58Co, 55Mn(α,2n)57Co, 59Co(α,2n)61Cu and 59Co(α,α2n)57Co nuclear reactions were carried out using the pre-equilibrium and equilibrium models. TALYS 1.9 and ALICE/ASH codes for the above nuclear reactions were used to describe the formation of the reaction process. Besides, the contribution on the cross section calculations of initial exciton number for alpha-induced reactions at the pre-equilibrium emissions is discussed. The results of this paper are compared with the measured nuclear data found in the literature. It was found that the initial exciton number n0 = 5 appears to give a good harmony to the measured values.

Theoretical determination of (d, n) and (d, 2n) excitation functions of some structural fusion materials irradiated by deuterons

Nuclear fusion is one of the world’s primary energy sources. Studies on the structural fusion materials are very important in terms of the development of fusion technology. Chromium, nickel, zinc, scandium, titanium, and yttrium are important structural fusion materials. In this paper, for use in nuclear science and technology applications, the excitation functions of the 50Cr(d, n)51Mn, 58Ni(d, n)59Cu, 64Zn(d, n)65Ga, 66Zn(d, n)67Ga, 45Sc(d, 2n)45Ti, 47Ti(d, 2n)47V, 48Ti(d, 2n)48V, and 89Y(d, 2n)89Zr nuclear reactions were investigated. The calculations that are based on the pre-equilibrium and equilibrium reaction processes were performed using ALICE–ASH computer code. A comparison with geometry-dependent hybrid model has been made using the initial exciton numbers n 0 = 4–6 and level density parameters α = A/5; A/8; A/11. Also, the present model-based calculations were compared with the cross sections obtained using the formulae suggested from our previous studies. Furthermore, the cross section results have been compared with TENDL data based on TALYS computer code and the measured data in the literature.

Studying the Nuclear Structure of Some Target Nuclei Used for Radiotherapy Nuclei Production by Using Skyrme-Hartree-Fock Method

The nuclear structure for some target nuclei namely: 32S, 58Ni, 89Y, 90Zr, 100Mo and 197Au used for production of the therapeutic radionuclides; 32P, 58Co, 89Sr, 90Y, 99Mo, 100Tc, 197Pt and 197Hg has been investigated using Skyrme-Hartree-Fock method based on Skyrme effective two-body interaction. For these purpose, we have calculated the various nuclear densities, the corresponding root mean square radii and nuclear binding energies. The density dependent initial neutron and proton exciton numbers have been also calculated which give the ability to investigate the neutron and proton induced reaction cross-sections for these target nuclei using hybrid model for pre-equilibrium nuclear reactions. The calculated results are compared with available experimental data.

Pre-equilibrium neutron-emission spectra of 238U with an effective nucleon–nucleon interactions

In this study, the initial exciton numbers for the target nucleus 238U were calculated through a new method offered by Tel et al. (Ann. Nucl. Energy, 35, 220, 2008). Neutron-emission spectra produced by (n,xn) reactions on 238U nuclei have been calculated by using Hartree–Fock method with effective nucleon–nucleon Skyrme interactions with SKM∗ parameters. Pre-equilibrium nuclear reactions have been used to investigate the effect of initial exciton numbers on the nucleon emission spectra. Calculations have been made in the framework of the hybrid, equilibrium and GDH models using ALICE/ASH computer code. The initial exciton numbers calculated with the theoretical neutron and proton densities have been obtained with SKM∗ for the 238U(n,xn) reaction at 14.0 and 18.0MeV incident neutron energies. We also compared the geometry-dependent hybrid model (GDH), newly evaluated with the initial exciton number calculations of the neutron emission spectra of the 238U(n,xn) reaction. The obtained results are discussed and compared with the available experimental data and are shown to be in agreement with each other. All calculated results have been compared with experimental data from Experimental Nuclear Reaction Data (EXFOR).

Photophysics in Single-Walled Carbon Nanotubes with (6,4) Chirality at High Excitation Densities: Bimolecular Auger Recombination and Phase-Space Filling of Excitons

The photophysics in single-walled carbon nanotubes (SWNTs) at high excitation densities has been attracting significant attention for exciton stability. Exciton–exciton interactions and an exciton Mott transition of quasi-one-dimensional excitons in SWNTs are of fundamental interest because the screening effect of the Coulomb interaction is suppressed in one-dimensional systems. In this study, we investigate exciton dynamics and a bimolecular Auger recombination process in SWNTs with (6,4) chirality using femtosecond transient absorption measurements at high excitation densities in the range of 2.4 × 1013–4.8 × 1015 photons cm–2 per pulse. Temporal evolutions of the change in the absorption coefficient are analyzed with an analytical expression for the bimolecular Auger recombination dynamics. We determine the Auger recombination coefficient and initial exciton number per tube, and the absorption cross section is also obtained. By using the phase-space filling model, the exciton size is estimated to be 3.1 ± 1.3 or 2.2 ± 1.0 nm, which depends on the corresponding wave function. Based on the estimated exciton size, the possibility of the Mott transition of quasi-one-dimensional excitons is discussed.

On the nuclear properties of 32S, 64Zn, 67Zn, 89Y, 90Zr and 153Eu targets used for production of 32P, 64Cu, 67Cu, 89Sr, 90Y and 153Sm therapeutic radionuclides

We have calculated the nuclear binding energy per particle, root mean square (rms) charge radii, neutron and proton densities, and density dependent initial exciton numbers of the target nuclei 32S, 64Zn, 67Zn, 89Y, 90Zr and 153Eu used for production of the therapeutic radionuclides 32P, 64Cu, 67Cu, 89Sr, 90Y and 153Sm. The calculations are performed using the Skyrme Hartree–Fock (SHF) and Skyrme–Hartree–Fock–Bogoliubov (SHFB) approximations based on an effective Skyrme force. The calculated results are discussed and compared with experimental data and with results obtained using relativistic mean field theory.

Pre-equilibrium Emission Spectra Calculations of 232Th(n,xn) Using New Evaluated Method

The knowledge of the thorium (232Th) cycle potentialities are required for the design of a fusion-fission (hybrid) reactor. Pre-equilibrium nuclear reactions have been used to investigate the effect of initial exciton numbers on the nucleon emission spectra. In this study, the initial exciton numbers for the target nucleus of 232Th were calculated through a method of offered by Tel et al. and then were used to obtain the effect cross section of the neutron emission spectra. Using this new method, a different way from the literature, the initial exciton numbers calculated with the theoretical neutron and proton densities have been obtained with SKM* on the 232Th(n,xn) reaction at 14.1 and 18.0 MeV incident neutron energies. The results were analyzed by comparing the empirical results in the literature.

Neutron skin effect of some Mo isotopes in pre-equilibrium reactions

The neutron skin effect has been investigated for even isotopes of molybdenum at 25.6 MeV 94 − 100Mo(p, xn) reaction using the geometry-dependent hybrid model of pre-equilibrium nuclear reactions. Here the initial neutron/proton exciton numbers were calculated from the neutron/ proton densities obtained from an effective nucleon–nucleon interaction of the Skyrme type. Initial exciton numbers from different radii of even Mo isotopes were used to obtain the corresponding neutron emission spectra. In this investigation the calculated results are compared with the experimental data as also with each other. The results using central densities in the geometry-dependent hybrid model are in better agreement with the experimental data.

The effect of the initial exciton numbers on 54,56Fe(p, xp) Pre-Equilibrium Reactions

In pre-equilibrium nuclear reactions, the geometry-dependent hybrid model is applied with the use of the neutron and proton densities to investigate the effect of initial exciton numbers on the nucleon emission spectra. The initial exciton numbers calculated with the theoretical neutron and proton densities have been obtained within the Skryme-Hartree-Fock method with SKM* and SLy4 forces on target nuclei in the 54,56Fe(p, xp) reaction at 61.5-MeV incident proton energy by using a new calculationmethod of Tel et al. Also, the differences between the initial exciton numbers for protons and neutrons as a function of nuclear radius, focusing on systematic discrepancies correlated to differences in the proton and neutron densities have been investigated.

Investigation of neutron skin effect with density dependence by using a new calculation method for initial exciton numbers on pre-equilibrium reactions

In this study, we investigated the pre-equilibrium effect by using a new evaluated geometry-dependent hybrid model and a neutron skin effect with density dependence for the 204,206,207Pb(p, xn) reaction at 25.5 MeV incident proton energy. We calculated the initial exciton numbers obtained from the modified Skyrme force based on fitting the fission barriers of heavy deformed nuclei (SKM*) and SLy4 for proton induced reaction on target nuclei 204,206,207Pb. We calculated, by using a new calculation method, the initial neutron and proton exciton numbers for 204,206,207Pb from the neutron and proton density and we investigated the shell effect by using an effective nucleon–nucleon interaction with Skyrme force. We also compared the geometry-dependent hybrid model (GDH), newly evaluated with the initial exciton number calculations of the neutron emission spectra of the 204,206,207Pb(p, xn) reaction, with the values reported in the literature at 25.5 MeV incident proton energy. The obtained results were investigated and compared with the pre-equilibrium calculations and experimental results.

Investigation of the nuclear structure of the Be, Cr and Cu isotopes

The Root-Mean-Square (RMS) nuclear charge, neutron and proton radii, charge, neutron and proton densities, neutron skin thickness and total binding energy per particle were calculated using the Hartree–Fock method with Skyrme forces for the chromium (Cr), copper (Cu) and beryllium (Be) isotopes. The obtained results were compared with the experiment. Additional to these calculations the initial neutron and proton exciton numbers for 52Cr isotope were also calculated. These exciton numbers can be used for pre-equilibrium proton induced (p, xn) reactions on 52Cr isotope.

Calculation of induced reactions of 3He-particles on natSb in 10–34 MeV energy range

Calculations for the excitation functions of the 121Sb( 3He, xn) 121,122,123I, and 123Sb( 3He xn) 122,123,124,125I reactions have been carried out using statistical and pre-equilibrium nuclear reaction models in 10−34 MeV energy range. These excitation functions have been used to derive the excitation functions of the natSb( 3He, xn) 121,123,124I reactions and compared with reported measurements. For studying the improvement with measurements two values of the diffuseness parameter a w equal to 0.9 and 0.7 fm have been used in the calculations. The dependence of pre-equilibrium calculations on the initial exciton numbers has also been considered.

New calculation method for initial exciton numbers on nucleon induced pre-equilibrium reactions

In this study, we investigate the pre-equilibrium effect by using new evaluated geometry dependent hybrid model for the {sup 208}Pb (p,xn) reaction at 25.5 and 62.9 MeV incident proton energies. We also suggest that the initial neutron and proton exciton numbers for the nucleon induced precompound reactions be calculated from the neutron and proton density by using an effective nucleon-nucleon interaction with Skyrme force. We calculate the initial exciton numbers obtained from SKM* and SLy4 for a proton induced reaction on target nuclei {sup 208}Pb. The obtained results have been investigated and compared with the pre-equilibrium calculations and experimental results.

Measurement and Analysis of Alpha Particle Induced Reactions on Praseodymium

Excitation functions (EFs) for the reaction 141 Pr(α, n ) 144 Pm and 141 Pr(α,2 n ) 143 Pm have been measured using 141 Pr as a target up to 50 MeV α-particle energy. Stacked foil activation technique and γ-ray spectroscopy using 100 cm 3 Ge (Li) detector, has been used. Excitation functions are also calculated theoretically using Blann's geometry dependent hybrid (GDH) model code ALICE-91, with and without inclusion of pre-equilibrium particle emission. It has been observed that high-energy tails of the EFs are dominated by pre-equilibrium reaction mechanism. With the accepted set of input parameter, initial exciton number n 0 =4 (2 p +2 n +0 h ), a good qualitative agreement is found. However, quantitative agreement for this magic nucleus 141 Pr is also good when theoretical calculations are normalized by a multiple factor of 0.5.

EXCITATION FUNCTIONS OF α-INDUCED REACTIONS IN COBALT AND PRE-EQUILIBRIUM EFFECTS

Excitation functions for the reactions (α,2n), (α,αn), (α,α2n), (α,α3n) and (α,2pn) have been measured using 57 Co as a target up to 50 MeV α-particle energy. The stacked foil activation technique and γ-ray spectroscopy method has been employed. Measured excitation functions are compared with the geometry dependent hybrid (GDH) model. A comparison shows that the pure equilibrium (EQ) compound reaction mechanism is incapable of reproducing the experimental data while the pre-equilibrium (PE) reaction mechanism along with equilibrium (EQ) decay, where it is considered that pre-equilibrium emission of particles take place prior to the establishment of the thermodynamical equilibrium of the system, is able to reproduce the experimental data. The GDH model code ALICE-91 has been used for theoretical calculations. A value of initial exciton number n0=4 with configuration (2 neutron + 2 proton + 0 hole) has been found to give the satisfactory reproduction of experimental excitation functions.

The181Ta(7Li,5n)183Osreaction: Measurement and analysis of the excitation function and isomeric cross-section ratios

Excitation function and isomeric cross-section ratios for the production of ${}^{183}{\mathrm{Os}}^{m,g}$ by ${}^{7}\mathrm{Li}$-induced reactions on ${}^{181}\mathrm{Ta}$ are obtained from the measurements of the residual activities by the conventional stacked-foils technique from threshold to 50 MeV. The excitation function and isomeric cross-section ratios for nuclear reaction ${}^{181}\mathrm{Ta}{(}^{7}\mathrm{Li}{,5n)}^{183}{\mathrm{Os}}^{m,g}$ are compared with the theoretical statistical model calculation by using the ALICE/91, STAPRE, and CASCADE codes. In the energy range of the present measurement the excitation functions are fitted fairly well by both the geometry dependent hybrid (GDH) model and the hybrid model of Blann with initial exciton number ${n}_{0}=7$ (${n}_{n}=4,$ ${n}_{p}=3,$ ${n}_{h}=0$) using the ALICE/91 code. The experimental isomeric cross-section ratios are also reproduced fairly well by the calculation using the STAPRE code. However, the CASCADE code calculations slightly underpredict the cross section but reproduce the shape. In general, the statistical model under a suitable set of global assumptions, can reproduce the excitation function as well as isomeric cross-section ratios.

Pre-equilibrium Model Analysis of Alpha Particle InducedReactions up to 80MeV

The excitation functions of the 51V[(α,n),(α,3n), (α,p3n), (α,α3n),(α,α2pn), (α,2α) and (α,2αn)]reactions were studied up to 80MeV using stacked foil activationtechnique and Ge(Li) gamma-ray spectroscopy. Secondly, a comparisonwith the pre-equilibrium hybrid model and the index model have beenmade using the initial exciton number n0 = 4(4p0h).It was observed that the hybrid model gives a better agreement thanthe index model for (α.xn) type of reactions. However,both the models failed to explain reactions involving the emission ofprotons and alpha particles.

Excitation function measurement and reaction mechanism analysis for alpha-induced reactions on

Excitation functions have been measured for and produced by -particle-induced reactions on in the incident energy range 34-50 MeV. The excitation functions of these nuclei and those of , reported earlier, are analysed in terms of direct, pre-equilibrium and evaporation emissions. The two most commonly used models of pre-equilibrium reactions, the exciton and the hybrid models, have both been used and compared. The choice of the initial exciton number, the role of the pre-equilibrium cluster and multiple nucleon emissions have been investigated. The direct emission of clusters are found to significantly affect the excitation functions of and Au isotopes.

α-particle induced reactions on yttrium and terbium

The stacked foil activation technique has been employed for the investigation of $\ensuremath{\alpha}$-particle induced reactions on the target elements yttrium and terbium up to 50 MeV. Six excitation functions for the $(\ensuremath{\alpha},xn)$ type of reactions were studied using high-resolution HPGe $\ensuremath{\gamma}$-ray spectroscopy. A comparison with Blann's geometric dependent hybrid model has been made using the initial exciton number ${n}_{0}=4(4p0h)$ and ${n}_{0}=5(5p0h)$. A broad general agreement is observed between the experimental results and theoretical predictions with an initial exciton number ${n}_{0}=4(4p0h)$.