Formation of the isomeric pairsNd139m,gandNd141m,gin proton andHe3-particle-induced nuclear reactions

Abstract

Cross sections were measured by the activation technique for the nuclear reactions $^{141}\mathrm{Pr}$($p,n$)$^{141}\mathrm{Nd}$${}^{m}$,$^{141}\mathrm{Pr}$($p,3n$)$^{139}\mathrm{Nd}$${}^{m},{}^{\mathrm{nat}}$Ce($^{3}\mathrm{He}$,$\mathit{xn}$)$^{141}\mathrm{Nd}$${}^{m}$, and ${}^{\mathrm{nat}}$Ce($^{3}\mathrm{He}$,$\mathit{xn}$)$^{139}\mathrm{Nd}$${}^{m}$ up to proton energies of 44 MeV and $^{3}\mathrm{He}$-particle energies of 35 MeV. Using the present data and some of our earlier experimental results the isomeric cross-section ratios for the nuclide pairs $^{139}\mathrm{Nd}$${}^{m,g}$ and $^{141}\mathrm{Nd}$${}^{m,g}$ were calculated. The experimental data were compared with the results of nuclear model calculations using the code STAPRE, which combines the statistical and precompound formalisms. In general the experimentally determined excitation functions as well as the isomeric cross-section ratios could be described by the theory within the limits of experimental uncertainties, but using relatively low values of $\ensuremath{\eta}$ [i.e., the ratio of the effective moment of inertia to the rigid-body moment of inertia (${\ensuremath{\Theta}}_{\mathrm{eff}}/{\ensuremath{\Theta}}_{\mathrm{rig}}$)]. The mass dependence of $\ensuremath{\eta}$ could be confirmed.