Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userCore Excited Fano-Resonances in Exotic Nuclei
84
0
0.0
(
0
)
Authors
S.E.A. Orrigo
Ask ChatGPT about the research
No Arabic abstract
Fano-resonances are investigated as a new continuum excitation mode in exotic nuclei. By theoretical model calculations we show that the coupling of a single particle elastic channel to closed core-excited channels leads to sharp resonances in the low-energy continuum. A signature for such bound states embedded in the continuum (BSEC) are characteristic interference effects leading to asymmetric line shapes. Following the quasiparticle-core coupling model we consider the coupling of 1-QP (one-quasiparticle) and 3-QP components and find a number of long-living resonance structures close to the particle threshold. Results for 15C are compared with experimental data, showing that the experimentally observed spectral distribution and the interference pattern are in qualitative agreement with a BSEC interpretation.
rate research
Read More
The atomic nucleus is a quantum many-body system whose constituent nucleons (protons and neutrons) are subject to complex nucleon-nucleon interactions that include spin- and isospin-dependent components. For stable nuclei, already several decades ago, emerging seemingly regular patterns in some observables could be described successfully within a shell-model picture that results in particularly stable nuclei at certain magic fillings of the shells with protons and/or neutrons: N,Z = 8, 20, 28, 50, 82, 126. However, in short-lived, so-called exotic nuclei or rare isotopes, characterized by a large N/Z asymmetry and located far away from the valley of beta stability on the nuclear chart, these magic numbers, viewed through observables, were shown to change. These changes in the regime of exotic nuclei offer an unprecedented view at the roles of the various components of the nuclear force when theoretical descriptions are confronted with experimental data on exotic nuclei where certain effects are enhanced. This article reviews the driving forces behind shell evolution from a theoretical point of view and connects this to experimental signatures.
The eXtended Continuum Discretized Coupled Channel (XCDCC) method is developed to treat reactions where core degrees of freedom play a role. The projectile is treated as a multi-configuration coupled channels system generated from a valence particle coupled to a deformed core which is allowed to excite. The coupled channels initial state breaks up into a coupled channels continuum which is discretized into bins, similarly to the original CDCC method. Core collective degrees of freedom are also included in the interaction of the core and the target, so that dynamical effects can occur during the reaction. We present results for the breakup of $^{17}$C=$^{16}$C+n and $^{11}$Be=$^{10}$Be+n on $^{9}$Be. Results show that the total cross section increases with core deformation. More importantly, the relative percentage of the various components of the initial state are modified during the reaction process through dynamical effects. This implies that comparing spectroscopic factors from structure calculations with experimental cross sections requires more detailed reaction models that go beyond the single particle model.
Recent experimental observation of magicity in $^{78}$Ni has infused the interest to examine the persistence of the magic character across the N$=$50 shell gap in extremely neutron rich exotic nucleus $^{78}$Ni in ground as well as excited states. A systematic study of Ni isotopes and N$=$50 isotones in ground state is performed within the microscopic framework of relativistic mean-field (RMF) and the triaxially deformed Nilson Strutinsky model (NSM). Ground state density distributions, charge form factors, radii, separation energies, pairing energies, single particle energies and the shell corrections show strong magicity in $^{78}$Ni. Excited nuclei are treated within the statistical theory of hot rotating nuclei where the variation of level density parameter and entropy shows significant magicity with a deep minima at N$=$50, which, persists up to the temperatures $approx$ 1.5$-$2 MeV and then slowly disappear with increasing temperature. Rotational states are evaluated and effect of rotation on N$=$50 (Z$=$20$-$30) isotones are studied. Our results agree very well with the available experimental data and few other theoretical calculations.
We present ab initio calculations of resonances for $^7$He, a nucleus with no bound states, using the realistic nucleon-nucleon interaction Daejeon16. For this, we evaluate the $n{-}{^6rm He}$ elastic scattering phase shifts obtained within an $S$-matrix analysis of no-core shell model results for states in the continuum. We predict new broad resonances likely related to fragmentary experimental evidence.
In highly dissipative collisions between heavy ions, the optimal conditions to investigate different de-excitation channels of hot nuclei such as evaporation, fission or multifragmentation are well known. One crucial issue remains the excitation energy region where fission gives way to multifragmentation. In this paper, the onset of multi-fragment exit channels is investigated in terms of sequential fission. For the first time, the dynamical approach based on solving Langevin transport equations in multidimensional collective coordinate space is used to follow the de-excitation of highly excited (up to E* =223-656 MeV) 248Rf compound nuclei. The sequential fission model we propose contains two steps: (1) time evolution of the compound nucleus up to either scission or residue formation, followed by (2) dynamical calculations of each primary fragment separately. This procedure allows to obtain from one to four cold fragments correlated with the light particles emitted during the de-excitation process. Experimental data measured with the INDRA detector for the 129Xe+ natSn reaction at beam energies 8, 12 and 15 MeV/nucleon provide strong constraints for this sequential fission scenario.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
