The giant dipole resonance at moderate temperature and spin

doi:10.1016/0375-9474(88)90572-6

Nuclear Physics A

Volume 482, Issues 1–2, May 1988, Pages 13-26

https://doi.org/10.1016/0375-9474(88)90572-6 Get rights and content

Abstract

The properties of the giant dipole resonance in heated nuclei at moderate spin and temperature are discussed, with emphasis on recent Seattle measurements and calculations. These new results emphasize the role of deformation fluctuations in determining the GDR shape.

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Cited by (25)

The angular-momentum dependence of the giant dipole resonance in 154Dy*
1994, Nuclear Physics, Section A
The statistical γ-ray decay of the compound nucleus ¹⁵⁴Dy^∗ formed at an excitation energy of 69 MeV is studied in three angular-momentum windows 〈J 〉 = 31,42 and 50ℏ. The GDR strength function extracted from the data indicates a constant centroid energy for the resonance E_GDR = 15.2 ± 0.5 MeV, a small deformation of the nuclear shape for all spin regions and an increase in the resonance width with increasing angular momentum. The latter might indicate larger shape fluctuations at higher angular momenta. A systematical study of the dependence of the extracted strength function with different methods of analysis is presented, and their discrepancies discussed.
The angular distribution of gamma-rays from thermal high-spin giant-dipole-resonances on superdeformed states
1993, Nuclear Physics, Section A
The microscopic approach with thermal RPA based on thermal CHFB ensemble is applied to the analysis of the angular distribution coefficient of γ-rays, a₂(E_γ), in addition to the spectrum shapes of σ_abs(E_γ), both for the ground band with small prolate deformation and for the superdeformed band in ¹³²Ce. The critical γ-ray energy where a₂(E_γ) changes its sign is much lower for the superdeformed band than for the ground band. Thermal energy-weighted sum-rule gives an account for the decrease of the peak height of σ_abs(E_γ) with increasing temperature.
The Giant Dipole Resonance at high excitation energy and spin
1993, Nuclear Physics, Section A
Observation of strongly deformed shapes in 154-152Dy nuclei at medium temperatures
1992, Physics Letters B
The γ-decay of the giant dipole resonance (GDR) built on excited states of ^154-152Dy nuclei is studied. The selection of GDR decay from high spin states leading to specific exit channels was made possible by triggering on high spin isomers. The deduced energy splitting of the GDR implies large deformations ( $|β|≌0.4–0.5$ ). The resonance widths of the components are comparable to those of the GDR built on the ground state indicating small shape fluctuations.
Calculation of the giant dipole resonance in hot nonspherical heavy nuclei with realistic forces
1992, Physics Letters B
Time-dependent fluctuations and the giant dipole resonance in hot nuclei: Solvable models
1991, Nuclear Physics, Section A
A recent macroscopic theory of time-dependent shape fluctuations in hot nuclei and their effects on the giant dipole resonance is investigated in the context of solvable models with one quadrupole shape degree of freedom. Using the framework of the Landau theory of shape transitions, both the quadrupole shape and the giant dipole degrees of freedom are described by a coupled set of stochastic equations. Two solvable models for which the dipole correlation function is found in closed form are discussed; one for a spherical nucleus and one for a deformed nucleus. The adiabatic and sudden limits of the models are examined. The latter limit is shown to produce a phenomenon known as motional narrowing. For the more general cases we introduce Monte Carlo techniques and test them against the solvable models.

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Nuclear Physics A

Abstract

References (17)

Nucl. Phys. A

Phys. Lett.

Nucl. Phys. A

Ann. Phys.

Ann. Rev. Nucl. Part. Sci.

Phys. Rev. Lett.

Cited by (25)

The angular-momentum dependence of the giant dipole resonance in <sup>154</sup>Dy<sup>*</sup>

The angular distribution of gamma-rays from thermal high-spin giant-dipole-resonances on superdeformed states

The Giant Dipole Resonance at high excitation energy and spin

Observation of strongly deformed shapes in <sup>154-152</sup>Dy nuclei at medium temperatures

Calculation of the giant dipole resonance in hot nonspherical heavy nuclei with realistic forces

Time-dependent fluctuations and the giant dipole resonance in hot nuclei: Solvable models