Weak and Electromagnetic Interactions in Nuclei pp 129-131 | Cite as

# Excitation of Stretched Particle-Hole States in Closed Shell Nuclei

## Abstract

High-spin states of unnatural parity have recently been observed in nuclei over a wide range of the nuclear charts by using various hadronic and leptonic reactions [1]. The high-spin states are expected to be generated by a simple particle-hole (p-h) configuration j_{p}j_{h} ^{-1}, where j_{p}=ℓ_{p}+1/2 and j_{h}=ℓ_{h}+1/2 are the largest angular momenta found in the first open shell and the last filled shell, respectively. When the j_{p} and j_{h} couple to the angular momentum of the maximum value J_{max}=j_{p}+j_{h}=ℓ_{p}+ℓ_{h}+1, the high-spin states are often referred to as stretched p-h states. A number of experimental data indicate that the excitation strengths of the stretched and nearly stretched p-h states are suppressed by a factor of 1/5–1/2 compared to those predicted by the single-particle shell model. Subnucleonic effects such as the isobar-hole excitations and the mesonic exchange currents are expected to be rather weak in the stretched transitions due to higher multipole transitions[2]. The observed quenching of the strengths might be therefore attributed mainly to nuclear structure effects, such as ground state correlations and higher-shell configuration mixing effects. Since the stretched state in a closed shell nucleus is a unique p-h state with the lℏω excitation, and since the number of configurations is severely limited due to high angular momentum of the state, a perturbative method would be applicable in order to estimate the nuclear structure effects. We attempt to make a systematic configuration mixing calculation of the transition strengths for the high-spin p-h states in the closed shell nuclei from ^{12}C to ^{208}Pb. Several calculations[3,4] have so far been made to interpret inelastic electron scattering form factors of the 14^{-} and 12^{-} states in ^{208}Pb.

## Keywords

Form Factor Transition Strength High Angular Momentum Large Angular Momentum Ground State Correlation## Preview

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## References

- 1.A. Lindgren: Journal de Physique, Supplement C4, 433 (1984)Google Scholar
- 2.T. Suzuki, S. Krewald and J. Speth: Phys. Lett. 107B, 9 (1981)ADSGoogle Scholar
- 3.I. Hamamoto, J. Lichtenstadt and G. F. Bertsch: Phys. Lett. 93B, 213 (1980)ADSGoogle Scholar
- 4.T. Suzuki, M. Oka, H. Hyuga and A. Arima: Phys. Rev. C26, 750 (1982)ADSGoogle Scholar
- 5.A. de Shalit and H. Feshbach: Theoretical Nuclear Physics (John Wiley & Sons, 1974)Google Scholar
- 6.H. Noya, A. Arima and H. Horie: Prog. Theor. Phys., Supplement 8, 33 (1958)CrossRefGoogle Scholar