MeV For States Research Articles

Study of the coherence widths Γ in 28Si measured by the 12C( 16O, α) reaction

States in 24Mg were populated by the 12C( 16O, α) 24Mg reaction. Excitation functions were measured in the bombarding energy range E c.m. = 17.1–19.7 MeV for states in 24Mg with excitation energies from 0 to 12 MeV. A fluctuation analysis of the excitation functions was made and the coherence widths Γ of the compound nuclear states were extracted. By comparing theoretical calculations of Γ with present and previous measurements values for the moment of inertia and the spin cutoff parameter of 28Si were extracted.

On the energy spectra of single-particle states in nuclei

The single-particle spectra of 16O, 40Ca, 48Ca and 56Ni have been studied using self- consistent field methods and a quadratically velocity-dependent two-nucleon effective (reaction- matrix) interaction. The self-consistent field equations are derived in some detail for the spin- independent interaction which is used. A one-body spin-orbit interaction of the Thomas form is added. The applicability of Koopmans' theorem to nuclear removal energies is discussed at some length. It is concluded that this theorem should be applied with caution. Orbital rearrangement energies are calculated and are found to be less than or about 0.2 MeV for states at the Fermi surface and 1–2 MeV for the deepest states.

Angular correlation analysis of the 58Ni(p, p′γ) reaction

Energy averaged angular distributions have been measured for 58Ni(p, p'γ) radiations at E p = 6.52 and 6.92 MeV for states up to 4.1 MeV excitation, using a Ge(Li)-NaI(Tl) coincidence-anticoincidence spectrometer. In order to obtain spin assignments and γ-ray multipolarities, the data were analysed in terms of χ 2 fits to predictions of statistical reaction theory. The present results, together with other recent measurements, lead to best energies and J π values for 58Ni levels: namely 1454.0±0.1 keV 2 1 +, 2459.1 ±0.34 1 +, 2775.2±0.22 2 +, 2901.8 ±0.2 1 1, 2942.4±0.20 2 +, 3037.6±0.32 3 +, 3263.4±0.22 4 +, 3420.3±0.33 1 (+), 3530.9±0.3, 3593.4±0.3 1 2 (+), 3620.0±0.44 2 +, 3774.4±0.43 2 (+), 3898.3±0.32 5 +, and 4107.7±0.3 2 6 (+). The previously accepted 4 + assignment for the 3530.9 keV level has been ruled out. Available information concerning the γ-ray branches, multipolarities and transition rates is discussed. Outstanding discrepancies with shell-model predictions for energy spectra and transition rates are pointed out, particularly with regard to the energies of the 1 1 and 1 2 levels and the puzzling γ-ray decay properties of the 0 + 2 state.