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Title: Probing nuclear shapes close to the fission limit with the giant dipole resonance in {sup 216}Rn

Abstract

The gamma-ray decay of the giant dipole resonance (GDR) in the compound nucleus {sup 216}Rn formed with the reaction {sup 18}O+{sup 198}Pt at the bombarding energy of 96 MeV was investigated. High-energy gamma-ray spectra in coincidence with both prompt and delayed low-energy transitions were measured. The obtained GDR width at the average temperature <T>{approx_equal}1 MeV was found to be larger than that at T=0 MeV and to be approximately constant as a function of spin. The measured width value of 7 MeV is found to be consistent with the predictions based on calculations of the nuclear shape distribution using the newest approach for the treatment of the fission barrier within the liquid drop model. The present study is the first investigation of the giant dipole resonance width from the fusion-evaporation decay channel in this nuclear mass range.

Authors:
; ; ; ; ; ;  [1]; ; ; ; ; ; ;  [2];  [3];  [4]; ;  [5];  [6]
  1. Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, ul. Radzikowskiego 152, 31-342 Cracow (Poland)
  2. Dipartimento di Fisica, Universita di Milano and INFN Sez. Milano, Via Celoria 16, 20133 Milan (Italy)
  3. Niels Bohr Institute, Blegdamsvej 15-17, 2100 Copenhagen (Denmark)
  4. Institute of Experimental Physics, Warsaw University, Warsaw (Poland)
  5. Institut de Recherches Subatomiques and Louis Pasteur University, 23 rue du Loess, BP28 F-67037, Strasbourg Cedex 2 (France)
  6. Department of Physics, 30BC04, University of Surrey, Guildford GU2 1XH (United Kingdom)
Publication Date:
OSTI Identifier:
20695815
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 70; Journal Issue: 6; Other Information: DOI: 10.1103/PhysRevC.70.064317; (c) 2004 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; COMPOUND NUCLEI; DIPOLES; ENERGY-LEVEL TRANSITIONS; EVAPORATION MODEL; FISSION; FISSION BARRIER; GAMMA RADIATION; GAMMA SPECTRA; GIANT RESONANCE; LIQUID DROP MODEL; MEV RANGE; NUCLEAR DECAY; OXYGEN 18 REACTIONS; PLATINUM 198 TARGET; RADON 216; SPIN

Citation Formats

Kmiecik, M., Maj, A., Brekiesz, M., Krolas, W., Meczynski, W., Styczen, J., Zieblinski, M., Million, B., Bracco, A., Camera, F., Benzoni, G., Leoni, S., Wieland, O., Brambilla, S., Herskind, B., Kicinska-Habior, M., Dubray, N., Dudek, J., and Schunck, N.. Probing nuclear shapes close to the fission limit with the giant dipole resonance in {sup 216}Rn. United States: N. p., 2004. Web. doi:10.1103/PhysRevC.70.064317.
Kmiecik, M., Maj, A., Brekiesz, M., Krolas, W., Meczynski, W., Styczen, J., Zieblinski, M., Million, B., Bracco, A., Camera, F., Benzoni, G., Leoni, S., Wieland, O., Brambilla, S., Herskind, B., Kicinska-Habior, M., Dubray, N., Dudek, J., & Schunck, N.. Probing nuclear shapes close to the fission limit with the giant dipole resonance in {sup 216}Rn. United States. doi:10.1103/PhysRevC.70.064317.
Kmiecik, M., Maj, A., Brekiesz, M., Krolas, W., Meczynski, W., Styczen, J., Zieblinski, M., Million, B., Bracco, A., Camera, F., Benzoni, G., Leoni, S., Wieland, O., Brambilla, S., Herskind, B., Kicinska-Habior, M., Dubray, N., Dudek, J., and Schunck, N.. 2004. "Probing nuclear shapes close to the fission limit with the giant dipole resonance in {sup 216}Rn". United States. doi:10.1103/PhysRevC.70.064317.
@article{osti_20695815,
title = {Probing nuclear shapes close to the fission limit with the giant dipole resonance in {sup 216}Rn},
author = {Kmiecik, M. and Maj, A. and Brekiesz, M. and Krolas, W. and Meczynski, W. and Styczen, J. and Zieblinski, M. and Million, B. and Bracco, A. and Camera, F. and Benzoni, G. and Leoni, S. and Wieland, O. and Brambilla, S. and Herskind, B. and Kicinska-Habior, M. and Dubray, N. and Dudek, J. and Schunck, N.},
abstractNote = {The gamma-ray decay of the giant dipole resonance (GDR) in the compound nucleus {sup 216}Rn formed with the reaction {sup 18}O+{sup 198}Pt at the bombarding energy of 96 MeV was investigated. High-energy gamma-ray spectra in coincidence with both prompt and delayed low-energy transitions were measured. The obtained GDR width at the average temperature <T>{approx_equal}1 MeV was found to be larger than that at T=0 MeV and to be approximately constant as a function of spin. The measured width value of 7 MeV is found to be consistent with the predictions based on calculations of the nuclear shape distribution using the newest approach for the treatment of the fission barrier within the liquid drop model. The present study is the first investigation of the giant dipole resonance width from the fusion-evaporation decay channel in this nuclear mass range.},
doi = {10.1103/PhysRevC.70.064317},
journal = {Physical Review. C, Nuclear Physics},
number = 6,
volume = 70,
place = {United States},
year = 2004,
month =
}
  • The present paper describes the measurement of high energy gamma rays ({approximately}5{endash}22 MeV) in the reaction {sup 16}O+{sup 181}Ta. Singles measurements were performed at {ital E}({sup 16}O)=84, 89, and 107 MeV and the multiplicity gated measurements along with the angular distributions were made at {ital E}({sup 16}O)=94 MeV. It is seen that the Tl nuclei are nonspherical at the excitation energies and spins relevant for the present work. The angular distribution data can be explained only by incorporating large orientation fluctuations. An attempt has been made to extract information on shape fluctuations directly from the {gamma} spectra. Under the restrictionmore » of using a common {open_quote}{open_quote}intrinsic{close_quote}{close_quote} strength function characterized by {ital E}{sub 0} and {Gamma}{sub 0} for the multiplicity gated data sets, a small increase of the effective mean deformation and a drive towards triaxiality ({gamma}{approximately} 30{degree}) with angular momentum is brought out. If this restriction is relaxed, however, the data can be understood also with a smaller value of {gamma}. The singles data can be understood within the same framework with a higher value of {Gamma}{sub 0}. {copyright} {ital 1996 The American Physical Society.}« less
  • The influence of alpha clustering on nuclear reaction dynamics is investigated using the giant dipole resonance (GDR) lineshape studies in the reactions {sup 20}Ne (E{sub lab}=145,160 MeV) + {sup 12}C and {sup 20}Ne (E{sub lab}=160 MeV) + {sup 27}Al, populating {sup 32}S and {sup 47}V, respectively. The GDR lineshapes from the two systems are remarkably different from each other. Whereas, the non-alpha-like {sup 47}V undergoes Jacobi shape transition and matches exceptionally well with the theoretical GDR lineshape estimated under the framework rotating liquid drop model (RLDM) and thermal shape fluctuation model (TSFM) signifying shape equilibration, for the alpha cluster {supmore » 32}S an extended prolate kind of shape is observed. This unusual deformation, seen directly via gamma decay for the first time, is predicted to be due to the formation of orbiting dinuclear configuration or molecular structure of {sup 16}O + {sup 16}O in the {sup 32}S superdeformed band.« less
  • The spectrum shape and the angular distribution of {gamma} rays from highly excited and rotating {sup 90}Zr and {sup 92}Mo compound nuclei were measured and analyzed. The results are in good agreement with theory including both intrinsic-shape fluctuations and shape-orientation fluctuations about an equilibrium shape which changes from spherical to oblate deformed with increasing spin.
  • High-energy {gamma} rays emitted by the decay of the hot compound nucleus {sup 194}Hg, formed in the reaction {sup 30}Si(142 MeV)+{sup 164}Dy, have been measured in coincidence with different residual nuclei. The measured spectra and the relative residual-nucleus cross sections were simultaneously analyzed with the statistical model. Calculations assuming contributions from a GDR in superdeformed states were also made. No clear evidence was found that superdeformed shapes seen at T=0 survive at average nuclear temperature {l_angle}T{r_angle}{approx_equal}1.3 MeV. Instead, an average nuclear deformation corresponding to {l_angle}{beta}{r_angle}=0.3 constant with spin has been deduced for 20{lt}I{lt}38 {h_bar} by comparing the measured width tomore » that predicted by the model of thermal shape fluctuations. {copyright} {ital 1999} {ital The American Physical Society}« less