Nuclear Physics A最新文献

The fission dynamics has been studied for a near super heavy compound nucleus ²⁶⁰Rf populated through ²⁸Si + ²³²Th reaction at an excitation energy of 85.7 MeV. Full momentum transfer binary events were separated from the transfer induced fission events. The contribution from transfer induced fission has been found to be $7\pm 2\text{\%}$. Mas ratio distribution, mass-total kinetic energy (TKE), and mass angle correlation have been extracted for the full momentum transfer events using two body kinematics. The experimentally extracted width of mass distribution is higher than the mass width calculated theoretically using the saddle-point model, which indicates the presence of non-compound nuclear fission in the reaction under study. The mass-TKE distribution obtained for ²⁶⁰Rf nucleus matches with the theoretical predictions from the Viola systematics and GEneral description of Fission observables (GEF) model. The mass-angle distribution for the reaction under study indicates no significant correlation between the mass and emission angles of the fission fragments.

The photon beam asymmetry of the ${}^{12}C{(\overrightarrow{\gamma },p_{01})}^{11}B$ and ${}^{12}C{(\overrightarrow{\gamma },p_{2-6})}^{11}B$ reactions has been measured in the energy range 40–65 MeV, using a tagged, linearly-polarized photon beam at the MAX-lab facility in Sweden. The asymmetry of the ${}^{12}C{(\overrightarrow{\gamma },p_{01})}^{11}B$ reaction to ground and first excited state of ${}^{11}B$ is $\Sigma \approx 0.82$ over the measured energy range. The main contribution to the ${}^{12}C{(\overrightarrow{\gamma },p_{2-6})}^{11}B$ reaction to higher excited states comes from processes in which the residual nucleus is in the $3/2^{-}$(5.02 MeV) or $7/2^{-}$(6.74 MeV) excited states. The asymmetry of this reaction is $\Sigma \approx 0.6$, close to the value for free deuteron photodisintegration.

Neutron energies and angular distributions were measured in ⁹Be(α,n)¹²C reaction for α energies of 5.5 and 6.5 MeV. Three major neutron groups were observed in the spectrum, which correspond to the ground and first two excited states of ¹²C. Measured data could only be explained by the TALYS calculation if reaction at more than one location within the target is considered for a given beam energy. The preferred locations are driven by the resonance energy levels existing in ¹³C. Neutron yield due to the ⁹Be breakup process was determined which is found to be 12.6 ± 0.2% and 18.4 ± 0.5% of the total reaction cross-section for 5.5 and 6.5 MeV respectively.

In this theoretical work, the ground state properties like binding energy per nucleon, two-neutron separation energy, two-neutron shell gap, neutron-pairing gap, neutron rms radii, proton rms radii, charge radii, neutron skin thickness and nucleon density distributions of odd-even and odd-odd gold isotopes (${}^{165-265}Au$) were systematically studied. Computations were performed for a wide mass range of gold nuclei, spanned from the proton-rich side to the neutron-rich side, following the Hartree-Fock-Bogoliubov theory. Based on this approach, the nuclear structure of gold isotopes lying up to the exotic neutron rich region where the experimental data are not available, was also investigated. Calculations, taking into account the UNEDF0 Skyrme effective interaction, reproduce the available experimental data and results of other nuclear model based estimations, such as the Relativistic-Continuum-Hartree-Bogoliubov theory and the Finite Range Droplet Models, reasonably well.

The rare-earth region has been the focus of various studies aiming at the understanding of nuclear structure and providing information on the details of the reaction mechanism. The Gd isotopes belong to this group of nuclei and despite the available spectroscopic information, several open questions about their structure still exist, such as the inter-band transitions related to shape evolution or branching-ratios in deformed states. In addition, production cross sections of different reactions to Gd isotopes are largely unknown.

In this work, we report on an experimental attempt to populate the excited states in the isotopes ^152,153,154Gd by employing the heavy-ion fusion reaction ¹⁸O+¹³⁸Ba → ^156-xGd + xn in the 58-64 MeV energy range (center-of-mass). The experiment was conducted at the 9 MV FV Pelletron Tandem at the Horia Hulubei National Institute for Physics and Nuclear Engineering, employing the ROSPHERE array. Several branching-ratios for energy levels in ^152,153Gd have been measured, offering new and updated values. Furthermore, relative cross sections regarding the fusion-evaporation reactions ¹³⁸Ba(¹⁸O, 4n)¹⁵²Gd, ¹³⁸Ba(¹⁸O, 3n)¹⁵³Gd, and ¹³⁸Ba(¹⁸O, 2n)¹⁵⁴Gd have been measured and compared with theoretical calculations with PACE4.

Within the relativistic mean field approximation, we analyse the kink effect (KE) in the evolution of the charge radius isotope shift of lead isotopes as a function of the neutron number N. We show that if the interactions between neutron and proton states responsible for the KE are assumed to be proportional either to the overlaps of their corresponding wave functions or to those of their corresponding probability density distributions, it is not possible, by themselves, to explain the KE. However, we find that the small component of the single-particle Dirac spinors plays a relevant role in the kink formation. By considering the contribution of the $N-126$ valence neutrons to the proton central potential, we can explain the generation of the KE and why neutrons in the $1i_{11/2}$ orbital are more kinky than when they are in the $2g_{9/2}$ orbital.