Excitation of Giant Resonances Via Direct Reactions
Excitation of Giant Resonances Via Direct Reactions

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Published: 1982

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Experimental measurements of electric giant multipole resonances are discussed. The parameters of the giant quadrupole resonance are now firmly established by an extensive set of measurements. The GQR is providing a significant influence in other areas of nuclear physics. The monopole resonance has now been established and its observation has provided the first direct measure of the nuclear compressibility. A strong case for the existence of a giant octupole resonance is now being made through a variety of hadron reactions. However, the supply of giant multipole resonances has not been exhausted. The newer techniques such as higher energy proton scattering, charge exchange reactions, heavy-ion scattering and pion reactions offer considerable hope for identifying new resonances during the next few years.

Excitation of Giant Resonances Via Charge Exchange Reactions
Excitation of Giant Resonances Via Charge Exchange Reactions

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Published: 1979

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Charge-exchange reactions can be useful for identifying isovector resonances. At present the most promising use of charge-exchange reactions with respect to giant resonances is to locate and study Gamow-Teller (GT) resonances. Detailed comparisons between GT and M1 strengths can yield further structure information. 7 figures.

Giant Resonances in Single and Double Charge Exchange
Giant Resonances in Single and Double Charge Exchange

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Published: 1991

Total Pages: 11

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A long-standing issue in nuclear physics is whether or not multiple excitations of the giant-dipole resonance do exist. Recent studies at LAMPF using pion-induced double-charge exchange reactions show the existence of previously unobserved giant resonances in the continuum at high-excitation energies. Based on their energies, characteristic angular distributions, and the cross sections at which the resonances are observed, they have been identified as two different types of double-collective-excitation modes of the nucleus: (1) The isovector giant-dipole resonance built on the isobaric analog state and (2) the isovector giant-dipole resonance built on the giant dipole. In this report we will discuss the general features of the new resonances as they have emerged from DCX experiments performed recently at LAMPF. 12 refs., 7 figs.

Giant Resonances
Giant Resonances

Author: P.F. Bortigan

Publisher: Taylor & Francis

Published: 2023-05-31

Total Pages: 290

ISBN-13: 1000940667

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The series of volumes, Contemporary Concepts in Physics, is addressed to the professional physicist and to the serious graduate student of physics. The subject of many-body systems constitutes a central chapter in the study of quantum mechanics, with applications ranging from elementary particle and condensed matter physics to the behaviour of compact stellar objects. Quantal size effects is one of the most fascinating facets of many-body physics; this is testified to by the developments taking place in the study of metallic clusters, fullerenes, nanophase materials, and atomic nuclei. This book is divided into two main parts: the study of giant resonances based on the atomic nucleus ground state (zero temperature), and the study of the y-decay of giant resonances from compound (finite temperature) nuclei.

Coupled-Channel Models of Direct-Semidirect Capture Via Giant-Dipole Resonances
Coupled-Channel Models of Direct-Semidirect Capture Via Giant-Dipole Resonances

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Published: 2013

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Semidirect capture, a two-step process that excites a giant-dipole resonance followed by its radiative de-excitation, is a dominant process near giant-dipole resonances, that is, for incoming neutron energies within 5 20 MeV. At lower energies such processes may affect neutron capture rates that are relevant to astrophysical nucleosynthesis models. We implement a semidirect capture model in the coupled-channel reaction code Fresco and validate it by comparing the cross section for direct-semidirect capture 208Pb(n, g)209Pb to experimental data. We also investigate the effect of low-energy electric dipole strength in the pygmy resonance. We use a conventional single-particle direct-semidirect capture code Cupido for comparison. Furthermore, we present and discuss our results for direct-semidirect capture reaction 130Sn(n, g)131Sn, the cross section of which is known to have a significant effect on nucleosynthesis models.

Recent Results from Proton Capture to Giant Resonances Built on Highly-excited States
Recent Results from Proton Capture to Giant Resonances Built on Highly-excited States

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Published: 1984

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New measurements of the (p, .gamma.) reaction on natural targets of K and Ca at intermediate proton energies (E/sub p/ = 11 to 36 MeV) reveal excitation functions that are dominated by excited-state giant dipole resonances (ESGDR's) built upon single-particle states in 4°Ca and 41Sc. These ESGDR's all peak near E/sub .gamma./ = 20 MeV and have widths which increase monotonically with the final state's excitation energy. The integrated, inverse (.gamma., P0) cross sections are shown to be proportional to the known single-particle spectroscopic strengths indicating a semi-direct mechanism for the capture process. 12 references, 13 figures.

Excitation and Photon Decay of Giant Multipole Resonances
Excitation and Photon Decay of Giant Multipole Resonances

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Published: 1990

Total Pages: 14

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A brief review of the excitation of giant multipole resonances via Coulomb excitation is given which emphasizes the very large cross sections that can be realized through this reaction for both isoscalar and isovector resonances. Discussion and results where available, are provide for the measurement of the photon decay of one and two phonon giant resonances. It is pointed out throughout the presentation that the use of E1 photons as a tag'' provides a means to observe weakly excited resonances that cannot be observed in the singles spectra. 14 refs., 12 figs., 1 tab.