Complete spectroscopy of51,52V via the50,51V(n, ?) reactions

Abstract

The gamma-ray spectra emitted after thermal neutron capture in highly enriched50V andnatV targets have been studied using in-pile targets at the ILL high flux reactor and pair and germanium detectors. The neutron binding energies in51V and52V were determined to beBn(51V)=11051.11(17) keV andBn(52V)=7311.22(26) keV. The thermal neutron capture cross-section in50V was measured to be 21−2+4 b. From 724 lines attributed to51V, 330 transitions, comprising 90% of theγ-ray flux, were placed into the level scheme. Fifty-nine primary dipole transitions from the 11/2+ or 13/2+ capture states in51V were established from which the E1 strength distribution was deduced. The energy scaling of these primary transitions was found to follow the E1-giant dipole resonance dominance. Many new levels were established; a number of states proposed in previous (d,p) and (n,γ) work were confirmed from their primary population and decaying secondary radiations. The density of levels in the high spin (9/2≦I≦15/2) region was parametrized with the Fermi gas model. The spin distributions of51V were analyzed and a spin cut-off parameter σ=2.8 (3) was deduced. — A nearly complete level scheme of52V up to 3.5 MeV excitation and similar results concerning the level density and the primary γ-ray spectrum were obtained in the51V (n, γ)52V study.