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Title: Excitation of Soft Dipole Modes in Electron Scattering

Abstract

The excitation of soft dipole modes in light nuclei via inelastic electron scattering is investigated. I show that, under the proposed conditions of the forthcoming electron-ion colliders, the scattering cross sections have a direct relation to the scattering by real photons. The advantages of electron scattering over other electromagnetic probes is explored. The response functions for direct breakup are studied with few-body models. The dependence on final-state interactions is discussed. A comparison between direct breakup and collective models is performed. The results of this investigation are important for the planned electron-ion colliders at the GSI and RIKEN facilities.

Authors:
 [1]
  1. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
931350
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review C; Journal Volume: 75
Country of Publication:
United States
Language:
English

Citation Formats

Bertulani, Carlos A. Excitation of Soft Dipole Modes in Electron Scattering. United States: N. p., 2007. Web. doi:10.1103/PhysRevC.75.024606.
Bertulani, Carlos A. Excitation of Soft Dipole Modes in Electron Scattering. United States. doi:10.1103/PhysRevC.75.024606.
Bertulani, Carlos A. Mon . "Excitation of Soft Dipole Modes in Electron Scattering". United States. doi:10.1103/PhysRevC.75.024606.
@article{osti_931350,
title = {Excitation of Soft Dipole Modes in Electron Scattering},
author = {Bertulani, Carlos A},
abstractNote = {The excitation of soft dipole modes in light nuclei via inelastic electron scattering is investigated. I show that, under the proposed conditions of the forthcoming electron-ion colliders, the scattering cross sections have a direct relation to the scattering by real photons. The advantages of electron scattering over other electromagnetic probes is explored. The response functions for direct breakup are studied with few-body models. The dependence on final-state interactions is discussed. A comparison between direct breakup and collective models is performed. The results of this investigation are important for the planned electron-ion colliders at the GSI and RIKEN facilities.},
doi = {10.1103/PhysRevC.75.024606},
journal = {Physical Review C},
number = ,
volume = 75,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • The excitation of soft dipole modes in light nuclei via inelastic electron scattering is investigated. I show that, under the proposed conditions of the forthcoming electron-ion colliders, the scattering cross sections have a direct relation to the scattering by real photons. The advantages of electron scattering over other electromagnetic probes is explored. The response functions for direct breakup are studied with few-body models. The dependence on final-state interactions is discussed. A comparison between direct breakup and collective models is performed. The results of this investigation are important for the planned electron-ion colliders at the GSI and RIKEN facilities.
  • Inelastic electron scattering form factors of the J/sup ..pi../ = 1/sup +/ states at excitation energies E/sub x/ = 5.800 and 5.846 MeV in /sup 206/Pb and /sup 208/Pb, respectively, are discussed in terms of a simple model of isoscalar-isovector mixing. It is known that for these states, which are often called loosely ''isoscalar'' 1/sup +/ states, about half of the transition strength is accounted for by this mixing. It is demonstrated here that the isoscalar-isovector mixing is also crucial for explaining the momentum dependence and the absolute magnitude of the form factor. The relative importance of the convection currentmore » contribution to the form factor with respect to the spin one is also studied. Finally, the isovector M1 strength distribution in /sup 206/Pb between E/sub x/ = 6.7--8.2 MeV derived from high resolution inelastic electron scattering is shown to agree in shape and magnitude with the one measured recently in an experiment with tagged polarized photons.« less
  • The Goldhaber-Teller model of the giant dipole resonance of a nucleus was cast in the language of the shellcollective model by using the generator coordinate method of Hill, Wheeler, and Griffin. The wave function for the excited state found in this way was used to evaluate explicitly the inelastic electron scattering form factor for excitation of the gaint dipole resonance of the nucleus. The form factor is found to be proportional to the elastic form factor multiplied by the momentum transfer. From an estimate of the bremsstrahlung background extracted from Fregeaus's data it is concluded that experimental investigation of themore » giant dipole resonance by electron scattering is feasible at optimum momentum transfer. (auth)« less
  • The cross section for the excitation of the nuclear giant resonance by electrons is calculated in a model in which the protons are assumed to oscillate as a unit against the neutrons. The longitudinal component of the field of the electrons is shown to have a cross section that agrees with results obtained previously by Fallieros, Ferrell and Pal. The transverse component is shown to have a form factor proportional to the elastic scattering form factor. Preliminary measurements in C, Al, and Kr with 41.5 Mev electrons scattered at 180 c- , where only the transverse component is present, showmore » cross sections smaller by about a factor of four than the calculated ones. For C and Al, these results are not surprising, because the Goldhaber-Teller model predicts a -absorption cross section that exhausts the dipole sum-rule and photonuclear experiments have shown that light elements fall considerably short of this. The discrepancy in the case of Kr could result from the failure of the Born approximation used in the theory. Another interesting possibility is that the Goldhaber-Teller model previously thought to be a fairly good description of the giant resonance in medium and heavy nuclei, is not correct in detail. (auth)« less
  • The lineshape of the [ital v]=0--1 vibrational mode in the high resolution electron energy loss spectrum of physisorbed O[sub 2] on Pt(111) shows discrete loss peaks attributed to a low frequency molecule-surface vibration and its overtones. The energy and angular dependence of these vibrations is consistent with the molecular negative ion resonance mechanism predicted by Gadzuk.