Partial level density of n-quasiparticle excitations, radiative strength functions and new experimental information on the dynamics of nuclear structure change in the B n range

Semiphenomenological approximation of the sums of experimental radiative strength functions for dipole gamma transitions of energy E γ below the neutron binding energy B n for mass numbers in the range 40 ≤ A ≤ 200

“…The excitation energy, corresponding to the positions of local peaks in the radiative strength functions of the considered nuclei (for E 1 > 1 MeV) is compared with the threshold energy of appearing four (five)-quasiparticle levels in Fig.5. Taking into account unavoidable errors and ambiguity of the analysis [11], their complete compliance with the position of one of the peaks is observed. In the first approximation in the scale of B n − E 1 the position of another one coincides with the energy of quadrupole phonons (for example, about 1 MeV for the deformed even-even nuclei) or the region of mainly one-or two-particle levels in even-odd and odd-odd nuclei, respectively.…”

“…Such possibility follows from the successful description [11,12] of the experimental data for ρ from [6,9] by the superposition of partial level densities, determined by nquasiparticle excitations with enhancement of the quasiparticle level densities of K vibr >> 1 times at the phonon type excitations expense of the ofdomination.…”

“…Namely, these are well described by ρ = ψ(E ex ) and k = φ(E 1 ) functions, the parameters of which differ sufficiently weak at changing of masses of the studied nuclei or when their changing does not contradict the unconditionally set theoretical notions about nucleus. A fraction of levels with purely dominating vibration components of wave functions (at least lower than ∼ 0.5B n ) is very significant [11,12]. However, the existing and practically used [15] models of the radiative strength functions do not completely take into account this fact.…”

“…The results are presented in Fig.1-4 for the main part of the studied by the present nuclei. Particular values of the parameters by the approximating curve for all nuclei [11,12] are given in the Table. Upon taking into account the type of compound state established by theory of components of wave function and laws of nuclear states fragmentation determining their value, the value of w parameter is to a greater or lesser extent determined by the structure of the wave function of neutron resonance. This implies that w parameter may change from resonance to resonance and, probably, correlate with values of their reduced neutron widths.…”

Completely model-free determination of the level density, radiative strength functions and their main peculiarities

“…Most probably it is caused [10] by breaking of two Cooper nucleon pairs at corresponding excitation energies of nucleus and change of their correlation function ∆ from maximum value to zero in the 2∆ 0 interval.…”