Comparission of E1 Response of 154Sm and 155Sm in the Pygmy Dipole Resonance (PDR) Region

Abstract

The dipole response associated with the pygmy dipole resonance (PDR) in ¹⁵⁴Sm and ¹⁵⁵Sm has been studied. In the ¹⁵⁴Sm nucleus 1^- phonons with K=0 and K=1 branches have been calculated using the Translation and Galilean Invariant Quasiparticle Random Phase Approximation (TGI-QRPA). The structure of the more pronounced electric dipole (E1) peaks in PDR region in ¹⁵⁴Sm is composed of predominantly two-quasiproton or two-quasineutron states. The calculations in ¹⁵⁵Sm has been performed in the framework of the Translation and Galilean Invariant Quasiparticle Phonon Nuclear Model (TGI-QPNM) based on the TGI-QRPA 1^- phonons calculated for ¹⁵⁴Sm. When going from ¹⁵⁴Sm to neighbouring ¹⁵⁵Sm, the fragmentation of the E1 strength is dramatically enhanced. The results emphasize the role of the quasiparticle⨂phonon interactions in enhancing the fragmentation of the strength in the PDR region in ¹⁵⁵Sm. Even though the strong fragmentation of the E1 strength obtained for ¹⁵⁵Sm, in 5-8 MeV energy region the summed E1 strength is comparable to that in ¹⁵⁴Sm. The results indicate that one quasiparticle behaves solely as a spectator in ¹⁵⁵Sm.

 

Keywords

• TGI-QRPA,TGI-QPNM,PDR,154Sm,155Sm,E1

Project Number

118F094

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