The level structure of 142Pr deduced from the 141Pr(n,γ)142Pr reaction

Abstract

A study of the low lying levels of 142Pr observed via the 141Pr(n,γ)142Pr reaction has revealed this nuclide to possess a much more complex structure than previously reported. Acquiring high precision spectra, which readily permitted detection of transitions with intensities greater than 0.01% and employing deconvolution techniques to achieve an effective resolution of 1 keV, resulted in identification of 455 transitions in the range of excitation energy 0 to 3500 keV. A constant temperature level density model, for which losses due to intensity and resolution effects are included, was used to describe the present results. Computations were undertaken to explore the validity of the assumptions made regarding the primary or secondary nature of the observed transitions. The models used to describe the spacing and intensity distributions in order to account for losses were verified through an examination of the experimental data. In addition, consideration of the degree of E1 and M1 contributions has been included. A high degree of self consistency of all these factors is demonstrated. An examination of the reduced radiative widths strongly suggests the influence of the giant dipole resonance. The precision of the energy measurements permitted the derivation of level energies with an average uncertainty of less than 100 eV. In addition to obtaining a neutron separation energy of 5843.14(10) keV for 142Pr, precise values were determined for nuclides 144Nd, 156Gd, 158Gd, and 208Pb.