dorsal/arxiv
View SchemaLarge-scale prediction of the parity distribution in the nuclear level density and application to astrophysical reaction rates
| Authors | D. Mocelj, T. Rauscher, G. Martinez-Pinedo, K. Langanke, L. Pacearescu, A. Faessler, F. -K. Thielemann, Y. Alhassid |
|---|---|
| Categories | |
| ArXiv ID | nucl-th/0703033 |
| URL | https://arxiv.org/abs/nucl-th/0703033 |
| DOI | 10.1103/PhysRevC.75.045805 |
| Journal | Phys.Rev.C75:045805,2007 |
Abstract
A generalized method to calculate the excitation-energy dependent parity ratio in the nuclear level density is presented, using the assumption of Poisson distributed independent quasi particles combined with BCS occupation numbers. It is found that it is crucial to employ a sufficiently large model space to allow excitations both from low-lying shells and to higher shells beyond a single major shell. Parity ratios are only found to equilibrate above at least 5-10 MeV of excitation energy. Furthermore, an overshooting effect close to major shells is found where the parity opposite to the ground state parity may dominate across a range of several MeV before the parity ratio finally equilibrates. The method is suited for large-scale calculations as needed, for example, in astrophysical applications. Parity distributions were computed for all nuclei from the proton dripline to the neutron dripline and from Ne up to Bi. These results were then used to recalculate astrophysical reaction rates in a Hauser-Feshbach statistical model. Although certain transitions can be considerably enhanced or suppressed, the impact on astrophysically relevant reactions remains limited, mainly due to the thermal population of target states in stellar reaction rates.
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"abstract": "A generalized method to calculate the excitation-energy dependent parity\nratio in the nuclear level density is presented, using the assumption of\nPoisson distributed independent quasi particles combined with BCS occupation\nnumbers. It is found that it is crucial to employ a sufficiently large model\nspace to allow excitations both from low-lying shells and to higher shells\nbeyond a single major shell. Parity ratios are only found to equilibrate above\nat least 5-10 MeV of excitation energy. Furthermore, an overshooting effect\nclose to major shells is found where the parity opposite to the ground state\nparity may dominate across a range of several MeV before the parity ratio\nfinally equilibrates. The method is suited for large-scale calculations as\nneeded, for example, in astrophysical applications. Parity distributions were\ncomputed for all nuclei from the proton dripline to the neutron dripline and\nfrom Ne up to Bi. These results were then used to recalculate astrophysical\nreaction rates in a Hauser-Feshbach statistical model. Although certain\ntransitions can be considerably enhanced or suppressed, the impact on\nastrophysically relevant reactions remains limited, mainly due to the thermal\npopulation of target states in stellar reaction rates.",
"arxiv_id": "nucl-th/0703033",
"authors": [
"D. Mocelj",
"T. Rauscher",
"G. Martinez-Pinedo",
"K. Langanke",
"L. Pacearescu",
"A. Faessler",
"F. -K. Thielemann",
"Y. Alhassid"
],
"categories": [
"nucl-th",
"astro-ph"
],
"doi": "10.1103/PhysRevC.75.045805",
"journal_ref": "Phys.Rev.C75:045805,2007",
"title": "Large-scale prediction of the parity distribution in the nuclear level density and application to astrophysical reaction rates",
"url": "https://arxiv.org/abs/nucl-th/0703033"
},
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