Two-quanta γ decays after thermal neutron capture in 139La nuclei

Decays covering two subsequent γ-transitions upon capture of thermal neutrons in 139La were studied. Eight distributions of the intensities of two-quantum decays completed by a number of low-lying levels or their close multiplets were obtained. Intensities and energies of γ-transitions were determined for 266 decays initiating 125 intermediate levels of 140La composite nucleus. Energy dependence of their intensity summed up as to all finite levels of decays was determined. Its comparison with the similar data for other nuclei demonstrated occurrence of smoothly varying at N variation from 82 up to 126 general rules of γ-decay process. They were interpreted in terms of the concept about the essential effect of vibration excitations on the nucleus structure and about their transition to excitations of quasi-partial type