Nuclear spectroscopy and study of pairing modes near N = 28 with the (τ, n) reaction

Abstract

Energy spectra and angular distributions of neutrons from the (τ, n) reaction on 48,50Ti, 50,52Cr, and 54Fe at 13 MeV bombarding energy have been measured with the time-of-flight technique. Altogether 65 new levels in the final nuclei have been observed. The DWBA analysis of the angular distributions yielded 56 new J π assignments, among them 26 levels with J π = 0 + and 27 levels with J π = 2 + The transitions to 0 + states have been compared with predictions of the shell model and the pairing model. The purely harmonic pairing vibration model gives correct predictions near 56Ni, but the agreement becomes worse with increasing distance from A = 56. The inclusion of anharmonicity effects, however, leads to a good overall description of all data (energies of ground and excited states, transitions strengths).