Results 1 - 10 of 12950
Results 1 - 10 of 12950. Search took: 0.028 seconds
|Sort by: date | relevance|
[en] We study the quadrupole moments and the B(E2; ) values for the states and the first states, respectively, by using a multi-j generalized seniority approach in the Cd (), Sn () and Te () isotopic chains. The g-factor trends have also been discussed. Although, Cd and Te isotopes represent two-proton hole and two-proton particle systems, thus involving both kind of particles (protons and neutrons) in contrast to Sn () where only neutrons play a role, we find that a similar model based on neutron valence space alone is able to explain nearly all the gross features and trends. This paper represents the first attempt to test the validity of the generalized seniority scheme away from the semi-magic region and appears to be surprisingly successful. The linearly varying quadrupole moments in Cd, Sn and Te isotopes, are described by using a consistent multi-j configuration. The asymmetric double-hump behavior of B(E2) values in Cd and Te isotopes are understood in a manner identical to that of Sn isotopes by using the generalized seniority scheme for the first time. No shell quenching is supported in the calculations; hence, the neutron magic numbers, and , remain robust in these isotopic chains.
[en] Parameters of the resonances , , , , and as well as the corresponding residues of the S-matrix are extracted from experimental data on elastic scattering. This is done by locating zeros of the Jost function at complex energies. The Jost function is constructed by fitting the corresponding partial cross sections for the elastic -scattering. These cross sections are obtained from the available R-matrix analysis of the raw experimental data. An exact semi-analytic representation for the Jost function is used, where all the factors responsible for the branching of the Riemann surface are given explicitly. The remaining unknown functions in this representation are approximated by several terms of the Taylor series where the expansion coefficients serve as the data-fitting parameters. Such an approximation does not affect the correct analytic structure of the Jost function, and thus the corresponding analytic structure of the S-matrix also remains correct.
[en] Fusion dynamics and the onset of quasi-fission in reactions, leading to production of superheavy nuclei are investigated using the constrained molecular dynamics model. Constraints on the parameters of the nuclear equation of state are derived from experimental fusion probabilities. The obtained constraint on the modulus of incompressibility of nuclear matter MeV is consistent with the results of previous study using the Boltzmann-Uehling-Uhlenbeck equation and also with constraints derived using the recent neutron star binary collision event GW170817. Unlike the modulus of incompressibility of symmetric nuclear matter, the stiffness of the density-dependence of symmetry energy influences the fusion probability only weakly.
[en] We study the pion-induced inclusive hyperon production from nuclei near threshold within a nuclear spectral function approach accounting for incoherent primary meson–proton production processes. We calculate the absolute differential and total cross sections for the production of hyperons off carbon and tungsten nuclei at laboratory angles of 0∘–10∘, 10∘–45∘ and 45∘–85∘ by mesons with momentum of 1.7 GeV/c as well as their relative (transparency ratio) differential and integral yields from these nuclei within four scenarios for their total in-medium width. We demonstrate that these absolute observables, contrary to the relative ones, reveal some sensitivity to the in-medium width. Therefore, their measurement in a dedicated experiment at the GSI pion beam facility will allow to shed light on this width.
[en] The response functions, S(E), and centroid energies, ECEN, of the isoscalar and isovector giant resonances of multipolarity L = 0–3 in 92,94,96,98,100Mo and 90,92,94Zr have been calculated employing the spherical Hartree-Fock (HF) based random phase approximation (RPA) method, using the Skyrme-type effective nucleon-nucleon interaction. In particular, we investigate the recent experimental results of the uncharacteristic behavior of ECEN for the isoscalar giant resonances, by extending our HF-based RPA calculations with only the KDE0v1 interaction to 32 additional Skyrme interactions. The main result of our investigation is that we find significant disagreements between the theoretical and the experimental values of ECEN for isoscalar giant monopole and dipole resonance of some nuclei. For the isoscalar giant octupole resonance we find the theoretical values of the ECEN to be well above the experimental results. We also study the sensitivity of ECEN to nuclear matter (NM) properties, including the effective mass, the incompressibility coefficient and the symmetry energy at saturation density, by determining the Pearson linear correlation coefficient between the calculated values of ECEN and the various nuclear matter properties of each Skyrme parametrization. For the isovector giant dipole resonance we find good agreement between the experimental and theoretical values of ECEN for Skyrme interactions with values of the enhancement coefficient of the energy weighted sum rule, κ, in the range between 0.25–0.70.
[en] In this paper, we study the evaporation residue cross section for superheavy elements using the phenomenological model taking into account the deformation and orientation effects of the target and the projectile. Calculations are done for the 3n and 4n channels in the reactions 54Cr+244−248,250Cm, 50V+245−250Bk, 55Mn+240−244Am, and 58Fe+240−242,244,246Pu. To test this model, we compared results of the 3n channel cross section in the reactions 48Ca+243Am, 48Ca+248Cm, 48Ca+249Bk and 48Ca+249Cf and the 4n channel cross section in the reactions 48Ca+243Am, 48Ca+248Cm, and 48Ca+249Bk with the experimental data. The agreement between the experimental data and the theoretical results based on deformed target and projectile is better than theoretical results for spherical target and projectile. Using this model, we predicted the maximum value and the corresponding energy of the 3n and 4n channel cross sections for spherical and deformed colliding nuclei for synthesizing Z=120. By applying the deformation effect and averaging over orientation, it is found that the maximum value of the 3n channel is 70.14 fb at 26.04 MeV for the reaction 54Cr+247Cm, whereas the maximum value of the 4n channel is 0.47 fb at 34.61 MeV for the reaction 54Cr+250Cm.
[en] We present a coupled channels separable potential approach to ηN and interactions using a chiral-symmetric interaction kernel. The s-wave πN amplitudes and induced total cross sections are reproduced satisfactorily in a broad interval of energies despite limiting the channel space to two-body interactions of pseudoscalar mesons with the baryon ground-state octet. It is demonstrated that an explicit inclusion of the meson singlet field leads to a more attractive ηN interaction, with the real part of the scattering length exceeding 1 fm. The diagonal coupling appears sufficient to generate an bound state but the inter-channel dynamics moves the respective pole far from the physical region making the interaction repulsive at energies around the channel threshold. The and resonances are generated dynamically and the origin and properties of the S-matrix poles assigned to them are studied in detail. We also hint at a chance that the state might also be formed provided a suitably varied model setting is found.
[en] The possibility of describing the available experimental data for the total cross section for the reaction of the neutron capture on 10B at energies from 25.3 meV to 1.0 MeV was considered in the framework of the modified potential cluster model with forbidden states, with the classification of the orbital cluster states according to Young diagrams and taking into account the resonance behavior of phase shifts of the B elastic scattering. The obtained results are found to be in agreement with the experimental measurements. The calculated total cross sections are used for obtaining the reaction rate of the neutron capture on 10B at the temperature range of 0.01 to 10 . The reaction rate increases essentially at temperatures above 0.3–0.4 , conditioned by the resonances at energy above 100 keV. The results obtained here demonstrate the validity of the used model to this reaction, without taking into account coupling of channels or the imaginary component of potential.
[en] Cluster decay half-lives of actinides ranging from 221Fr to 242Cm are studied with a model where MGLDM (Modified Generalized Liquid Drop Model) includes pre-formation factor which depends on size of cluster and daughter nucleus and also on iso-spin parameter. Theoretical prediction could replicate experimental values with a standard deviation of about 0.569. Also we checked the applicability of our model in the case of alpha decay and obtained exactly matching results. Then we make prediction of half-lives of several clusters which are not detected experimentally so far so that this will be very helpful for future investigation in this field.
[en] We investigate the effect of variation of nuclear surface diffuseness, through diffuseness parameter, on the evaluation of survival probability, absorption effects, Coulomb excitation cross section and total nuclear reaction cross section of Au system. The diffuseness parameter is found to be affecting all the above mentioned quantities appreciably. Specifically, the survival probability and Coulomb excitation cross section are found to be decreasing with increase in a while absorption effects and are found to be increasing.