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Title: Spin dependence of the giant-dipole-resonance strength function in highly excited nuclei in the mass region A =39--45

Abstract

Continuum {gamma}-ray spectra and angular distributions from decays of highly excited {sup 39}K, {sup 40}K, {sup 42}Ca, and {sup 45}Sc compound nuclei produced by bombarding {sup 27}Al with {sup 12}C, {sup 13}C, {sup 15}N, and {sup 18}O ions have been measured and the giant-dipole-resonance strength function has been extracted. The effective temperature associated with the states upon which the giant dipole resonance is built is nearly constant (1.7--1.8 MeV) for these reactions, while the final average spin varies from 8 to 18.5{h bar} as the projectile energy varies from 32 to 72.5 MeV. The parameters of the giant-dipole-resonance strength function extracted from fits of statistical model calculations to the {gamma}-ray spectra measured at {theta}{sub {gamma}}=90{degree} provide direct information on the spin dependence of the hot nuclear shape. The mean energy of the giant dipole resonance shows a weak spin dependence that has a different character for {sup 39}K and {sup 45}Sc nuclei. The width of the giant dipole resonance increases rapidly with spin for all reactions studied, from 11.6{plus minus}0.3 MeV at 8{h bar} to 14.7{plus minus}0.5 MeV at 18.5{h bar} for {sup 45}Sc{sup *} at {ital T}{sub {ital f}}=1.7--1.8 MeV, for example, presumably due to rotational broadening of themore » giant dipole resonance. For the reactions {sup 12}C+{sup 27}Al at {ital E}{sub lab}=62.7 MeV and {sup 18}O+{sup 27}Al at {ital E}{sub lab}=44.9 and 72.5 MeV, angular distributions have been measured. The observed energy dependence of the {ital a}{sub 2} coefficient suggests large nuclear deformation consistent with oblate noncollective or prolate collective rotation. The level density in nuclei with {ital A}{congruent}40 has been calculated in the Reisdorf approach with parameters fitted to low-energy level density data for nuclei in this mass region.« less

Authors:
 [1]; ; ; ; ;  [2]
  1. Institute of Experimental Physics, University of Warsaw, 00681 Warsaw, (Poland) Nuclear Physics Laboratory, University of Washington, Seattle, Washington 98195 (USA)
  2. Nuclear Physics Laboratory, University of Washington, Seattle, Washington 98195 (USA)
Publication Date:
OSTI Identifier:
7095691
Resource Type:
Journal Article
Journal Name:
Physical Review, C (Nuclear Physics); (USA)
Additional Journal Information:
Journal Volume: 41:5; Journal ID: ISSN 0556-2813
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; ALUMINIUM 27 TARGET; CARBON 12 REACTIONS; CARBON 13 REACTIONS; NITROGEN 15 REACTIONS; OXYGEN 18 REACTIONS; CALCIUM 42; GIANT RESONANCE; HEAVY ION FUSION REACTIONS; POTASSIUM 39; POTASSIUM 40; SCANDIUM 45; ANGULAR DISTRIBUTION; COMPOUND NUCLEI; GAMMA DECAY; MEV RANGE 10-100; NUCLEAR DEFORMATION; SPIN; STATISTICAL MODELS; STRENGTH FUNCTIONS; ALKALI METAL ISOTOPES; ALKALINE EARTH ISOTOPES; ANGULAR MOMENTUM; BETA DECAY RADIOISOTOPES; BETA-MINUS DECAY RADIOISOTOPES; BETA-PLUS DECAY RADIOISOTOPES; CALCIUM ISOTOPES; CHARGED-PARTICLE REACTIONS; DECAY; DEFORMATION; DISTRIBUTION; ELECTRON CAPTURE RADIOISOTOPES; ENERGY RANGE; EVEN-EVEN NUCLEI; FUNCTIONS; HEAVY ION REACTIONS; INTERMEDIATE MASS NUCLEI; ISOMERIC TRANSITION ISOTOPES; ISOTOPES; LIGHT NUCLEI; MATHEMATICAL MODELS; MEV RANGE; NUCLEAR DECAY; NUCLEAR REACTIONS; NUCLEI; ODD-EVEN NUCLEI; ODD-ODD NUCLEI; PARTICLE PROPERTIES; POTASSIUM ISOTOPES; RADIOISOTOPES; RESONANCE; SCANDIUM ISOTOPES; STABLE ISOTOPES; TARGETS; YEARS LIVIN; 651520* - Nuclear Properties & Reactions, A=39-58, Experimental

Citation Formats

Kicinska-Habior, M, Snover, K A, Behr, J A, Feldman, G, Gossett, C A, and Gundlach, J H. Spin dependence of the giant-dipole-resonance strength function in highly excited nuclei in the mass region A =39--45. United States: N. p., 1990. Web. doi:10.1103/PhysRevC.41.2075.
Kicinska-Habior, M, Snover, K A, Behr, J A, Feldman, G, Gossett, C A, & Gundlach, J H. Spin dependence of the giant-dipole-resonance strength function in highly excited nuclei in the mass region A =39--45. United States. doi:10.1103/PhysRevC.41.2075.
Kicinska-Habior, M, Snover, K A, Behr, J A, Feldman, G, Gossett, C A, and Gundlach, J H. Tue . "Spin dependence of the giant-dipole-resonance strength function in highly excited nuclei in the mass region A =39--45". United States. doi:10.1103/PhysRevC.41.2075.
@article{osti_7095691,
title = {Spin dependence of the giant-dipole-resonance strength function in highly excited nuclei in the mass region A =39--45},
author = {Kicinska-Habior, M and Snover, K A and Behr, J A and Feldman, G and Gossett, C A and Gundlach, J H},
abstractNote = {Continuum {gamma}-ray spectra and angular distributions from decays of highly excited {sup 39}K, {sup 40}K, {sup 42}Ca, and {sup 45}Sc compound nuclei produced by bombarding {sup 27}Al with {sup 12}C, {sup 13}C, {sup 15}N, and {sup 18}O ions have been measured and the giant-dipole-resonance strength function has been extracted. The effective temperature associated with the states upon which the giant dipole resonance is built is nearly constant (1.7--1.8 MeV) for these reactions, while the final average spin varies from 8 to 18.5{h bar} as the projectile energy varies from 32 to 72.5 MeV. The parameters of the giant-dipole-resonance strength function extracted from fits of statistical model calculations to the {gamma}-ray spectra measured at {theta}{sub {gamma}}=90{degree} provide direct information on the spin dependence of the hot nuclear shape. The mean energy of the giant dipole resonance shows a weak spin dependence that has a different character for {sup 39}K and {sup 45}Sc nuclei. The width of the giant dipole resonance increases rapidly with spin for all reactions studied, from 11.6{plus minus}0.3 MeV at 8{h bar} to 14.7{plus minus}0.5 MeV at 18.5{h bar} for {sup 45}Sc{sup *} at {ital T}{sub {ital f}}=1.7--1.8 MeV, for example, presumably due to rotational broadening of the giant dipole resonance. For the reactions {sup 12}C+{sup 27}Al at {ital E}{sub lab}=62.7 MeV and {sup 18}O+{sup 27}Al at {ital E}{sub lab}=44.9 and 72.5 MeV, angular distributions have been measured. The observed energy dependence of the {ital a}{sub 2} coefficient suggests large nuclear deformation consistent with oblate noncollective or prolate collective rotation. The level density in nuclei with {ital A}{congruent}40 has been calculated in the Reisdorf approach with parameters fitted to low-energy level density data for nuclei in this mass region.},
doi = {10.1103/PhysRevC.41.2075},
journal = {Physical Review, C (Nuclear Physics); (USA)},
issn = {0556-2813},
number = ,
volume = 41:5,
place = {United States},
year = {1990},
month = {5}
}