Systematics of the pygmy resonance in keV neutron capture γ-ray spectra of nuclei with N ≈ 82–126

Igashira, M.; Kitazawa, H.; Shimizu, M.; Komano, H.; Yamamuro, N.

doi:10.1016/0375-9474(86)90380-5

Systematics of the pygmy resonance in keV neutron capture γ-ray spectra of nuclei with N ≈ 82–126

1986

16 pages

Published in:

Nucl.Phys.A 457 (1986) 301-316

Published: 1986

DOI:

10.1016/0375-9474(86)90380-5

View in:

Nuclear Science References

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Abstract: (Elsevier)

We have measured capture gamma-ray spectra of Pr, Tb, Ho, Lu, Ta and Au at neutron energies of 10 to 800 keV with an anti-Compton NaI(Tl) detector, employing a time-of-flight technique. An anomalous bump, so-called the pygmy resonance, was observed in all these spectra. Remarkable features of the pygmy resonance were found to be that the resonance energy and the electric-dipole strength exhausted in the resonance increase with neutron number but these quantities decrease precipitously around the neutron magic number of N = 82. Comparison with theoretical calculations suggests that the pygmy resonance is mainly made up of neutron particle-hole states decoupled from the giant electric-dipole resonance and is excited in a collective mode.

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