Partial level density of the n-quasiparticle excitations in the nuclei of the 39< A <201 region

Level density and radiative strength functions are obtained from the analysis of two-step cascades intensities following the thermal neutrons capture. The data on level density are approximated by the sum of the partial level densities corresponding to n quasiparticles excitation. The most probable values of the collective enhancement factor of the level density are found together with the thresholds of the next Cooper nucleons pair breaking. These data allow one to calculate the level density of practically any nucleus in given spin window in the framework of model concepts, taking into account all known nuclear excitation types. The presence of an approximation results discrepancy with theoretical statements specifies the necessity of rather essentially developing the level density models. It also indicates the possibilities to obtain the essentially new information on nucleon correlation functions of the excited nucleus from the experiment.Comment: 29 pages, 8 figures, 2 table

Extended Hauser-Feshbach Method for Statistical Binary-Decay of Light-Mass Systems

An Extended Hauser-Feshbach Method (EHFM) is developed for light heavy-ion fusion reactions in order to provide a detailed analysis of all the possible decay channels by including explicitly the fusion-fission phase-space in the description of the cascade chain. The mass-asymmetric fission component is considered as a complex-fragment binary-decay which can be treated in the same way as the light-particle evaporation from the compound nucleus in statistical-model calculations. The method of the phase-space integrations for the binary-decay is an extension of the usual Hauser-Feshbach formalism to be applied to the mass-symmetric fission part. The EHFM calculations include ground-state binding energies and discrete levels in the low excitation-energy regions which are essential for an accurate evaluation of the phase-space integrations of the complex-fragment emission (fission). In the present calculations, EHFM is applied to the first-chance binary-decay by assuming that the second-chance fission decay is negligible. In a similar manner to the description of the fusion-evaporation process, the usual cascade calculation of light-particle emission from the highly excited complex fragments is applied. This complete calculation is then defined as EHFM+CASCADE. Calculated quantities such as charge-, mass- and kinetic-energy distributions are compared with inclusive and/or exclusive data for the $^{32}$S+$^{24}$Mg and $^{35}$Cl+$^{12}$C reactions which have been selected as typical examples. Finally, the missing charge distributions extracted from exclusive measurements are also successfully compared with the EHFM+CASCADE predictions.Comment: 34 pages, 6 Figures available upon request, Phys. Rev. C (to be published

Fragment Deexcitation of Fission Induced by High Energy Nucleons

The KRIF library of the neutron-, proton- and gamma-spectra emitted by the nuclei excited up to 500 MeV is presented. The KRIF contains information for about 2000 emitters which are the fragments of the ten targets fission induced by the nucleons with the energies up to 3 GeV

Description of fission yields in the nucleon-induced fission reactions

The potential model for the fission fragment mass distributions and simplified approach for the isobaric charge distribution are proposed for the description of fission yields (FY). The intermediate energy reaction code MCFx was used for the calculation of the fissionning nuclei distribution after fast (cascade), preequilibrium and statistical reaction stages. Formation of the mass distributions is considered as a result of oscillations on mass asymmetry degree of freedom in the potential well calculated with the temperature dependent shell correction method. The comparison of calculation results with the experimental data on FY for both low and intermediate energy fission show a good agreement of the data and let us conclude that the approach proposed may be useful for FY evaluations for experimentally unknown fission yields data in the case of the intermediate energy nucleon-induced fission

Description of Nucleon Induced Fission in Intranuclear Cascade -Multiparticle Preequilibrium - Hauser-Feshbach Approach

The MCFx code system for the description of neutron- and proton-induced fission of heavy nuclei in energy region 20-3000 MeV is presented. The approach integrates the optical model for reaction crosssection calculations, intranuclear cascade for description of fast particle escape, exciton model for multiparticle emission of preequilibrium nucleons and Hauser-Feshbach calculations for statistical description of fission/evaporation competition. New results of systematic calculations of fission cross-sections, multiplicities and double-differential spectra of secondary particles for Pb-Cm targets irradiated by neutrons and protons with energy 20-3000 MeV are discussed