The nuclear photoeffect in holmium and erbium

Fuller, E. G.; Hayward, Evans

doi:10.1016/0029-5582(62)90081-0

Cited by 86 publications

(12 citation statements)

References 17 publications

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“…The estimated uncertainties are ±0. 5 MeV in E C G and ±0.7 MeV in T£. In the case of the 84-MeV 16 0 reaction, an increase of Tg from 6.0 to 6.5 MeV produces a better fit.…”

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confidence: 87%

“…At low excitation energy, for resonances built on the ground state, it is well known that the shape of the GDR reflects the shape of the nucleus. 5 The average resonance energy is related to the nuclear symmetry energy and in deformed nuclei the resonance is split into components corresponding to vibrations along the three principal nuclear axes. In rotating nuclei, because of the Coriolis force, the resonance is further divided into a total of five components.…”

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confidence: 99%

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Nuclear Shape at High Spin and Excitation Energy

et al. 1984

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High-energy gamma rays from the deexcitation of giant dipole resonance modes have been measured for the decay of 108 Sn* and 166 Er*. The structure of the observed resonances can be correlated with the shapes of these nuclei at high excitation energy (E* -60 MeV). For the deformed system 166 Er* a shape change with increasing temperature is suggested. PACS numbers: 21.10. Gv, 24.30.Cz, 25.70.Gh The shapes of nuclei arise from basic correlations in nuclear matter. It is important to study these correlations and find the limits where they break down. This is possible to do by subjecting the nucleus to extreme conditions, such as high rotation and internal exciation energy, and studying the shapes which then result. Much work has been done in recent years both theoretically and experimentally to understand the shapes of "cold" nuclei. This work expands these studies to the mostly unexplored region of high nuclear temperature.A recent development 1 in continuum spectroscopy has provided a new tool for studying high spin spin states in the unbound region where gamma-ray emission, although weak, can compete with particle evaporation. It relies on the observation of highenergy y rays (E y^\ 0 MeV) emitted predominantly in the first stages of the decay of compound nuclei formed in heavy-ion-induced fusion reactions. These gamma rays have been associated with the deexcitation of giant dipole isovector resonance (GDR) modes. This has been substantiated 1,2 by comparing the measured cross section for gamma decay to the predictions of the classical dipole sum rule. The dependence of the GDR strength on excitation energy E* has been studied, 3 and the GDR yield from the first step of the decay has been isolated. 4 The results are consistent with the statistical theory for nuclear decay and indicate that the observed GDR decay is from equilibrated systems.In the present work we use this tool to study the shapes of nuclei in regions of excitation energy not otherwise accessible. At low excitation energy, for resonances built on the ground state, it is well known that the shape of the GDR reflects the shape of the nucleus. 5 The average resonance energy is related to the nuclear symmetry energy and in deformed nuclei the resonance is split into components corresponding to vibrations along the three principal nuclear axes. In rotating nuclei, because of the Coriolis force, the resonance is further divided into a total of five components. However, because of the small Coriolis splitting and the finite widths of these components, only two major peaks can be expected to be identified experimentally for axially symmetric nuclei. For prolate nuclei approximately -y of the total GDR strength is expected to be found in the peak of highest energy, while the situation is reversed for oblate nuclei.This investigation focuses on the structure of the GDR up to excitation energies E* -60 MeV and angular momenta IH -AQH, and we find a significant difference in the shape and width of the GDR built on excited states between the (at T = 0 MeV)...

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“…The estimated uncertainties are ±0. 5 MeV in E C G and ±0.7 MeV in T£. In the case of the 84-MeV 16 0 reaction, an increase of Tg from 6.0 to 6.5 MeV produces a better fit.…”

mentioning

confidence: 87%

mentioning

confidence: 99%

Nuclear Shape at High Spin and Excitation Energy

et al. 1984

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“…i"c is an incoherent contribution to the elastic scattering cross section arising from nuclear scattering from the GDR [15]. It is related to the tensorial term of elastic scattering and corresponds to the transfer of two units of angular momentum in the scattering process.…”

Section: Experiments With Ti Neutron Capture 7-raysmentioning

confidence: 99%

“…In the present case of low level densities we define the amplitude for coherent scattering by A =AR+AD+AT+A N (15) where A N is real and takes care of the contributions of all distant levels, capable of being excited via E 1 transitions from the ground state. This procedure Except for the 7.168MeV level in 2~ which appears not to have a strong transition to excited states, we were able to establish decay schemes for at least the stronger resonances.…”

Section: Nuclear Resonance Fluorescencementioning

confidence: 99%

Nuclear photoexcitation and delbr�ck scattering studied in the energy range 2?8 MeV

et al. 1981

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Elastic scattering by nuclei in the range of mass numbers between 64 and 238 has been studied with monochromatic photons in the energy range between 2 and 8 MeV. These photons were provided either by a Ti(n,7) source installed in the tangential through channel of the Grenoble high flux reactor, or by 24Na and S6Co sources produced by deuteron bombardment of A1 or Fe at the G6ttingen cyclotron. The photoexcitation of 23 nuclear levels has been observed and the decay properties and groundstate widths of the majority of these levels have been determined. For the lead scattering target the coherent elastic differential cross section has been studied in detail. There is evidence that below the photo-neutron threshold the elastic scattering via virtual photoexcitation of the nucleus can be approximated by extrapolating the real part of the Giant Dipole Resonance amplitude along a Lorentzian curve. Coulomb corrections to Delbrtick scattering seem to play a small role at 6.5 MeV.

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“…The only structure allowed by the collective modei Is a gross splitting of the giant resonance Into two resonances corresponding to oscillations along the major and minor axes of a deformed nucleus. Experimental studies of deformed nuclei, particu larly (8), IS^Eu (9), (9) and '®^Er (10) have found structure…”

Section: Experimental Apparatus 29mentioning

confidence: 99%

A systematic study of the photo-disintegration of germanium isotopes

McCarthy

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The nuclear photoeffect in holmium and erbium

Cited by 86 publications

References 17 publications

Nuclear Shape at High Spin and Excitation Energy

Nuclear Shape at High Spin and Excitation Energy

Nuclear photoexcitation and delbr�ck scattering studied in the energy range 2?8 MeV

A systematic study of the photo-disintegration of germanium isotopes

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