Observation of very large electromagnetic dissociation cross sections

Hill, J. C.; Wohn, F. K.; Schwellenbach, David; Smith, Alan Р.

doi:10.1016/0370-2693(91)90285-x

Cited by 19 publications

(18 citation statements)

References 20 publications

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“…17 shows that this expectation could be verified: the soft-spheres calculation for 1n-removal from 197 Au by ED processes (upper full curve) is almost indistinguishable from a sharp-cutoff calculation using b BCV min (upper dotted curve). This remarkable agreement tells us that for practical purposes we can avoid the extra numerical complication connected with the use of a soft spheres model and corroborates the use of b BCV min in sharp-cutoff calculations in earlier works [47,48]. We also think that the soft-spheres calculation (and the sharp-cutoff calculation using b BCV min ) is physically better justified than the Kox parametrization [44] since the former is derived from realistic nuclear density distributions, whereas the latter is an extrapolation of measured total reaction cross sections into a region where no data points are available.…”

Section: Nucleon Removal In Peripheral Relativistic Heavy Ion Collisionssupporting

confidence: 86%

Microscopic studies of two-phonon giant resonances

Ponomarev

1999

Nuclear Physics A

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A new class of giant resonances in nuclei, namely double giant resonances, is discussed. They are giant resonances built on top of other giant resonances. Investigation on their properties, together with similar studies on low-lying two-phonon states, should give an answer on how far the harmonic picture of boson-type excitations holds in the finite fermion systems like atomic nuclei.The main attention in this review is paid to double giant dipole resonances (DGDR) which are observed in relativistic heavy ion collisions with very large cross sections. A great experimental and theoretical effort is underway to understand the reaction mechanism which leads to the excitation of these states in nuclei, as well as the better microscopic understanding of their properties. The Coulomb mechanism of the excitation of single and double giant resonances in heavy ion collision at different projectile energies is discussed in details. A contribution of the nuclear excitation to the total cross section of the reaction is also considered. The Coulomb excitation of double resonances is described within both, the second-order perturbation theory approach and in coupled-channels calculation. The properties of single and double resonances are considered within the phenomenologic harmonic vibrator model and microscopic quasiparticle-RPA approach. For the last we use the Quasiparticle-Phonon Model (QPM) the basic ideas and formalism of which are presented. The QPM predictions of the DGDR properties (energy centroids, widths, strength distributions, anharmonicities and excitation cross sections) are compared to predictions of harmonic vibrator model, results of other microscopic calculations and experimental data available. : 24.30.Cz, 25.70.De, Pacs

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Section: Nucleon Removal In Peripheral Relativistic Heavy Ion Collisionssupporting

confidence: 86%

Microscopic studies of two-phonon giant resonances

Ponomarev

1999

Nuclear Physics A

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“…cr, "' is the experimental electromagnetic cross section from Refs. [9,11]. o ww is the cross section calculated using the WW (first-order dipole) approximation [given in Eq.…”

Section: Theorymentioning

confidence: 99%

“…o'""p' is the experimental total (electromagnetic plus nuclear) cross section from Refs. [9,11]. o. x, +z2+o.…”

Section: Comparison Between Theory and Experimentsmentioning

confidence: 99%

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Explanation of recent observations of very large electromagnetic dissociation cross sections. II. Higher order corrections

Norbury

Baur

1993

Phys. Rev. C

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Hill, Wohn, Schwellenbach, and Smith have recently measured very large electromagnetic dissociation cross sections in the collisions of very heavy nuclei. Weizsacker-Williams (WW) theory predicts that these cross sections should be even larger. It has recently been shown that WW theory fails for these reactions because the associated probabilities are too large. However, WW theory is based on first order perturbation theory and an electric dipole approximation. Calculations are presented which show that for those cases where WW theory and experiment disagree, higher order perturbation plus electric quadrupole corrections improve the agreement between theory and experiment. These corrections also imply that multiple electromagnetic excitations occur.PACS number(s): 25.75.+ r, 12.20.Ds

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“…Further experiments gave evidence for electromagnetic dissociation in the fragmentation of lSO projectiles at E/A = 1.7 GeV [4] and of 197Au targets excited by various projectiles [5,6]. Electromagnetic multiphonon excitations of the same targets were studied measuring the ln, 2n and 3n removal cross sections [7,8]. In other experimtents the "/-ray and neutron decay of the electromagnetically excited double giant-dipole resonance (GDR) in 2~ and 136Xe was observed [9,10,11].…”

Section: Introductionmentioning

confidence: 96%

Electromagnetic fission of238U at 600 and 1000 MeV per nucleon

Rubehn

Müller

Bassini³

et al. 1995

Z. Physik A - Hadrons and Nuclei

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Abstract. Electromagnetic fission of 23Su projectiles at E/A = 600 and 1000 MeV was studied with the ALADIN spectrometer at the heavy-ion synchrotron SIS. Seven different targets (Be, C, A1, Cu, In, Au and U) were used. By considering only those fission events where the two charges added up to 92, most of the nuclear interactions were excluded. The nuclear contributions to the measured fission cross sections were determined by extrapolating from beryllium to the heavier targets with the concept of factorization. The obtained cross sections for electromagnetic fission are well reproduced by extended Weizs~icker-Williams calculations which include E1 and E2 excitations. The asymmetry of the fission fragments' charge distribution gives evidence for the excitation of the double giant-dipole resonance in uranium.

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Observation of very large electromagnetic dissociation cross sections

Cited by 19 publications

References 20 publications

Microscopic studies of two-phonon giant resonances

Microscopic studies of two-phonon giant resonances

Explanation of recent observations of very large electromagnetic dissociation cross sections. II. Higher order corrections

Electromagnetic fission of238U at 600 and 1000 MeV per nucleon

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