dorsal/arxiv
View SchemaPopulation of isomers in decay of the giant dipole resonance
| Authors | N. Tsoneva, Ch. Stoyanov, Yu. P. Gangrsky, V. Yu. Ponomarev, N. P. Balabanov, A. P. Tonchev |
|---|---|
| Categories | |
| ArXiv ID | nucl-th/9909039 |
| URL | https://arxiv.org/abs/nucl-th/9909039 |
| DOI | 10.1103/PhysRevC.61.044303 |
| Journal | Phys.Rev. C61 (2000) 044303 |
Abstract
The value of an isomeric ratio (IR) in N=81 isotones ($^{137}$Ba, $^{139}$Ce, $^{141}$Nd and $^{143}$Sm) is studied by means of the ($\gamma, n)$ reaction. This quantity measures a probability to populate the isomeric state in respect to the ground state population. In ($\gamma, n)$ reactions, the giant dipole resonance (GDR) is excited and after its decay by a neutron emission, the nucleus has an excitation energy of a few MeV. The forthcoming $\gamma$ decay by direct or cascade transitions deexcites the nucleus into an isomeric or ground state. It has been observed experimentally that the IR for $^{137}$Ba and $ ^{139}$Ce equals about 0.13 while in two heavier isotones it is even less than half the size. To explain this effect, the structure of the excited states in the energy region up to 6.5 MeV has been calculated within the Quasiparticle Phonon Model. Many states are found connected to the ground and isomeric states by $E1$, $E2$ and $M1$ transitions. The single-particle component of the wave function is responsible for the large values of the transitions. The calculated value of the isomeric ratio is in very good agreement with the experimental data for all isotones. A slightly different value of maximum energy with which the nuclei rest after neutron decay of the GDR is responsible for the reported effect of the A-dependence of the IR.
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"abstract": "The value of an isomeric ratio (IR) in N=81 isotones ($^{137}$Ba, $^{139}$Ce,\n$^{141}$Nd and $^{143}$Sm) is studied by means of the ($\\gamma, n)$ reaction.\nThis quantity measures a probability to populate the isomeric state in respect\nto the ground state population. In ($\\gamma, n)$ reactions, the giant dipole\nresonance (GDR) is excited and after its decay by a neutron emission, the\nnucleus has an excitation energy of a few MeV. The forthcoming $\\gamma$ decay\nby direct or cascade transitions deexcites the nucleus into an isomeric or\nground state. It has been observed experimentally that the IR for $^{137}$Ba\nand $ ^{139}$Ce equals about 0.13 while in two heavier isotones it is even less\nthan half the size. To explain this effect, the structure of the excited states\nin the energy region up to 6.5 MeV has been calculated within the Quasiparticle\nPhonon Model. Many states are found connected to the ground and isomeric states\nby $E1$, $E2$ and $M1$ transitions. The single-particle component of the wave\nfunction is responsible for the large values of the transitions. The calculated\nvalue of the isomeric ratio is in very good agreement with the experimental\ndata for all isotones. A slightly different value of maximum energy with which\nthe nuclei rest after neutron decay of the GDR is responsible for the reported\neffect of the A-dependence of the IR.",
"arxiv_id": "nucl-th/9909039",
"authors": [
"N. Tsoneva",
"Ch. Stoyanov",
"Yu. P. Gangrsky",
"V. Yu. Ponomarev",
"N. P. Balabanov",
"A. P. Tonchev"
],
"categories": [
"nucl-th"
],
"doi": "10.1103/PhysRevC.61.044303",
"journal_ref": "Phys.Rev. C61 (2000) 044303",
"title": "Population of isomers in decay of the giant dipole resonance",
"url": "https://arxiv.org/abs/nucl-th/9909039"
},
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