Testing the modified dependence of the radiative strength function on different excitation energies in the light nucleus 28Al

The spectrum of random functions of level density as well as radiative strength functions of dipole E1- and M1-transitions of 28Al were determined. Obtained functions can reproduce very precisely the intensity of the two-step cascade following the radiative capture of thermal neutrons for a given energy of the primary transitions. The density of the observed intermediate levels can be reproduced correctly using the mean value of these functions. In this work we proposed a new hypothesis about the dependence of radiative strength functions for gamma-transitions in heated nucleus on the energy of excited levels. The results provide a solid basis that this new hypothesis allows to get realistic estimation on the parameters of nuclear structure in any nucleus, including the light ones.

LORENTZIAN-LIKE MODELS OF E1 RADIATIVE STRENGTH FUNCTIONS

Photoabsorption cross sections and dipole γ-decay strength functions are calculated and compared with experimental data to test Lorentzian-like models of their description in the middle-weight and heavy atomic nuclei. Approaches with asymmetric shape of the radiative strength function are recommended for overall estimation of the dipole γ-strengths. The ready-to-use table of giant dipole resonance parameters and their errors are obtained from fitting the theoretical calculations for photoabsorption cross sections to the experimental data. Systematics for giant dipole resonance parameters are given.

THE SIMPLIFIED DESCRIPTION OF DIPOLE RADIATIVE STRENGTH FUNCTION

The gamma-decay strength function is calculated and compared with experimental data to test simple methods of the descriptions of the dipole radiative strength function (RSF) of gamma-decay in the middle-weight and heavy atomic nuclei. Simplified version of the modified Lorentzian model is proposed. It is shown that the phenomenological closed-form models with asymmetric shape can be used for overall estimates of the dipole RSF in the gamma-ray energy region up to about 20 MeV when giant dipole resonance (GDR) parameters are known or the GDR systematics can be adopted.

COMPARISON AND TESTING OF METHODS FOR E1 STRENGTH CALCULATIONS

Extensive comparisons of E1 strength calculations within framework of the various methods are performed in atomic nuclei near beta-stability line. Photoabsorption cross-sections are calculated and compared with experimental data to test radiative strength function models.