PYGMY dipole resonance in 232Th, 236U and 238U

The E1 response of 232Th, 236U and 238U actinide nuclei below the particle threshold were studied using transitional and Galilean invariant quasi particle random-phase approximation. Especially strength properties of the pygmy dipole resonanse (PDR) with spin and parity are investigated and studied their contribution to 6-10 MeV region. The question discussed whether the pygmy dipole resonances are like the GDR collective states in the microscopic definition. The calculated total width for the spin-flip resonances states are about a factor of 10-2 weaker than the summed width of the states during PDR at this energy region and cannot concurrences with PDR. The results that have been obtained for E1 dipole excitations indicate the importance of the separation of the spurious center-of-mass motion of the nucleus for a correct description of the PDR