Shell-structure and asymmetry effects in level densities
| Autor: | A. I. Sanzhur, Shalom Shlomo, A. I. Levon, Alexander G. Magner, S. N. Fedotkin |
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| Rok vydání: | 2021 |
| Předmět: |
Physics
Nuclear and High Energy Physics Nuclear Theory Proton Computer Science::Information Retrieval media_common.quotation_subject F.2 Astrophysics::Instrumentation and Methods for Astrophysics Nuclear structure General Physics and Astronomy Semiclassical physics FOS: Physical sciences Computer Science::Computation and Language (Computational Linguistics and Natural Language and Speech Processing) Nuclear system Asymmetry Nuclear physics Nuclear Theory (nucl-th) Computer Science::General Literature Particle Neutron Energy (signal processing) media_common |
| DOI: | 10.48550/arxiv.2109.01830 |
| Popis: | Level density $\rho(E,N,Z)$ is derived for a nuclear system with a given energy $E$, neutron $N$, and proton $Z$ particle numbers, within the semiclassical extended Thomas-Fermi and periodic-orbit theory beyond the Fermi-gas saddle-point method. We obtain $~~\rho \propto I_\nu(S)/S^\nu$,~~ where $I_\nu(S)$ is the modified Bessel function of the entropy $S$, and $\nu$ is related to the number of integrals of motion, except for the energy $E$. For small shell structure contribution one obtains within the micro-macroscopic approximation (MMA) the value of $\nu=2$ for $\rho(E,N,Z)$. In the opposite case of much larger shell structure contributions one finds a larger value of $\nu=3$. The MMA level density $\rho$ reaches the well-known Fermi gas asymptote for large excitation energies, and the finite micro-canonical limit for low excitation energies. Fitting the MMA $\rho(E,N,Z)$ to experimental data on a long isotope chain for low excitation energies, due mainly to the shell effects, one obtains results for the inverse level density parameter $K$, which differs significantly from that of neutron resonances. Comment: 26 pages, 3 figures, 1 table. arXiv admin note: text overlap with arXiv:2103.16480 |
| Databáze: | OpenAIRE |
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