High-spin states and evidence for hole-core coupling in the 143Sm 81 and 145Gd 81 nuclei

Abstract

The level structure of the 143Sm and 145Gd nuclei has been studied using the 142Nd (α, 3nγ) 143Sm and 144Sm(α, 3nγ) 145Gd reactions. Singles γ-ray, γ-γ coincidence spectra, angular and time distributions with respect to the beam burst have been measured. Gamma transitions between excited states with spin values up to 29 2 in 143Sm and up to 21 2 in 145Gd have been observed. The observed level structure in both nuclei can be explained if the neutron-hole is coupled to the doubly even core excitations. The coupling of the h 11 2 neutron-hole with the 2 + and 3 − vibrations is calculated in the weak and intermediate coupling models. The results obtained in these calculations are in reasonably good agreement with the experimental data. The energies of the three-particle states, being the result of the coupling of the h 11/2 neutron-hole with the two-proton excitations in the core, are nicely reproduced in the calculations. Empirical values of the two-body interaction matrix elements have been used. However, the three-particle calculation does not explain the existence of the 30 ms 23 2 − isomeric level in the 143Sm nucleus.