Phase-space selection of the GDR gamma ray emission from hot 162Yb nuclei

doi:10.1016/0370-2693(92)91392-M

Physics Letters B

Volume 291, Issue 4, 1 October 1992, Pages 385-390

https://doi.org/10.1016/0370-2693(92)91392-M Get rights and content

Abstract

The angular distribution of the high energy gamma rays emitted in the decay of the giant dipole resonance built on excited states, in mainly ¹⁶²Yb, has been measured using a differential technique to enhance decays originating from the highest region of nuclear temperatures. A simple formalism to analyze such data is presented. Such experiments provide information on the shapes and orientation distribution of atomic nuclei at finite temperature.

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Cited by (13)

The giant dipole resonance strength and width at high temperature
2001, Nuclear Physics A
Excited states in 161,162Yb seen as mass asymmetric nuclear molecules
1996, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
GDR γ-ray decay in 156Dy* from regions selected on temperature and angular momentum
1995, Physics Letters B
The strength distribution of the GDR built on highly excited states in a restricted temperature domain in ¹⁵⁶Dy and ¹⁵⁵Dy nuclei has been deduced by subtraction of γ-ray spectra obtained for the decay of ¹⁵⁴Dy^∗ and ¹⁵⁶Dy^∗ from regions selected on angular momentum. The resulting difference spectra have been analyzed within the statistical model. The results show a large deformation (|β| ∼ 0.51±0.29 and 0.35±0.14) for the angular-momentum regions with $〈J〉 ∼ 32 h ̵$ at T ≈ 1.8±0.2 MeV and $〈J〉 ∼ 46 h ̵$ at T ≈ 1.7±0.2 MeV, respectively, in satisfactory agreement with calculations performed in the framework of Landau theory of shape transitions and statistical fluctuations. The deduced centroid energies are in agreement with the systematics of the GDR built on the ground state. The width of the GDR shows a systematic increase with increasing temperature.
Isomer-selected decay of the GDR in 156Dy*
1995, Nuclear Physics, Section A
The strength distribution of high-energy γ-rays emitted in the statistical decay of the ¹⁵⁶Dy^∗ compound nucleus, with $E^{∗} = 92.5 MeV$ , has been measured inclusively and for selected decay pathways in which isomers in ¹⁴⁹Dy, ¹⁵¹Dy and ¹⁵²Dy were populated. For both spectra a deformation |β| = 0.3 is deduced and the centroid energies agree with those found from ground-state systematics. The high-energy γ-ray spectrum triggered on isomeric decay shows an increase of the width of the GDR in comparison with the inclusive spectrum.
Large effects of orientation fluctuations in the angular distribution of the GDR photons
1994, Nuclear Physics, Section A
Measurements of the angular distribution of high energy γ rays emitted in the decay of compound nuclei ^165–167Er, ^175,176Hf, ¹¹⁰Sn at $E^{∗} = 50–90 MeV and I ≤ 40$ are presented. In all cases the measured anisotropies as a function of the gamma transition energy are small. The compound nuclei were formed with heavy ion fusion reactions and the high energy y rays were detected by the HECTOR array. A comparison between the data and model predictions shows that both shape and orientation fluctuations are very important and must be taken into account to reproduce the experimental results. The dominant role played by orientation fluctuations on the GDR lineshape and the effective induced nuclear deformations are discussed.
Angular distribution of photons from the delay of the GDR in hot and rotating light Yb nuclei from exclusive experiments
1994, Nuclear Physics, Section A
Angular distributions of photons associated with the damping of excited-state giant dipole resonances (GDR) in hot and rotating ^161,162Yb nuclei have been measured in exclusive experiments using the HECTOR array. In reactions with heavy ions (⁴⁸T) angular distributions are determined as a function of the angular momentum of the compound nuclei. In reactions with lighter ions (^17,18O) a difference method is applied to isolate GDR decays originating from specific excitation regions. The systematics of the measured angular distributions as a function of excitation energy and angular momentum are compared to theories taking into account fluctuations of the shape and orientation of the excited nuclei.

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^☆: This work has been supported by the Danish Carlsberg Foundation, the Danish Natural Science Research Council and the Italian Istituto Nazionale di Fisica Nucleare (INFN). The authors are indebted to Y. Alhassid, Yale, for the Landau parameters used in the shape calculations in this work and to F. Camera, Milan, and W. Korten, NBI, for inspiring discussions.

¹: Permanent address: Niewodniczanski Institute of Nuclear Physics, PL-31 342 Cracow, Poland.

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Physics Letters B

Abstract

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Cited by (13)

The giant dipole resonance strength and width at high temperature

Excited states in <sup>161,162</sup>Yb seen as mass asymmetric nuclear molecules

GDR γ-ray decay in <sup>156</sup>Dy<sup>*</sup> from regions selected on temperature and angular momentum

Isomer-selected decay of the GDR in <sup>156</sup>Dy<sup>*</sup>

Large effects of orientation fluctuations in the angular distribution of the GDR photons

Angular distribution of photons from the delay of the GDR in hot and rotating light Yb nuclei from exclusive experiments

Phase-space selection of the GDR gamma ray emission from hot 162Yb nuclei☆

Abstract

Nucl. Phys. A

Nucl. Phys. A

Phys. Rev. Lett.

Annu. Rev. Nucl. Part. Sci.

Annu. Rev. Nucl. Part. Sci.

Phys. Rev. Lett.

Phys. Rev. Lett.

Phys. Rev. C

Phys. Rev. Lett.

Phase-space selection of the GDR gamma ray emission from hot ¹⁶²Yb nuclei☆