The electric dipole response of even-even ^154–164Dy isotopes

Abstract

The excitation of pygmy dipole resonance (PDR) and giant dipole resonance (GDR) in even-even 154-164Dy isotopes is examined through quasiparticle random-phase approximation (QRPA) with the effective interactions that restores the broken translational and Galilean invariances. In each isotope, an electric response emerges by showing ample distribution at energies below and above 10 MeV. We, therefore, study the transition cross sections and probabilities, photon strength functions, transition strengths, isospin character, and collectivity of the predicted E1 responses.

Microscopic calculation of the electromagnetic dipole strength for 239,243Pu isotopes

“…In odd-A nuclei, the ΔK=±1 component of the E1 operator can couple the { } = K I K , 0 0 0 ground state to four excited levels with quantum numbers {( ) ( 243 Pu is distributed almost evenly between the K π =7/2 − and K π =9/2 − states, with both having excitation energy 10.60 MeV (appendix C). Indeed, as in the doubly even nuclei [97,98], these two isotopes' first and second peaks in the GDR spectra are concentrated in the ΔK=0 and the ΔK=±1 E1 strengths, respectively. In the PDR energy region, the E1 peaks feature a dominant single-quasiparticle⊗phonon configuration with ΔK=0 and ΔK=±1 .…”

“…Tables that include the quasiparticle⊗phonons configurations paired with several one-quasiparticle components are also given in appendices C and D. Here, the lm Q i phonon operator λ represents the multipole degree of vibration, μ stands for the angular momentum projection on the symmetry axis, and i symbolizes the phonon number. In the TGI-QRPA phonon structure [97,98], the electric dipole states are mainly given by pure neutron and/or proton two-quasiparticle configurations. In odd-A nuclei, the ΔK=±1 component of the E1 operator can couple the { } = K I K , 0 0 0 ground state to four excited levels with quantum numbers {( ) ( 243 Pu is distributed almost evenly between the K π =7/2 − and K π =9/2 − states, with both having excitation energy 10.60 MeV (appendix C).…”

Effectiveness of the TGI-QRPA approach for studying the electric dipole response

“…The advantage of QRPA-based approaches is that they can in principle be applied to all nuclei other than a few very light systems, and they are successful and accurate at reproducing observed quantities. Among QRPA-based approaches we could mention translational and Galilean invariant (TGI)-QRPA [1][2][3][4][5][6][7][8][9][10], the self-consistent QRPA approach based on Skyrme [11][12][13][14][15][16][17][18], and the relativistic density functional QRPA [19][20][21][22][23][24] and QRPA on Gogny force [25][26][27][28], to name but a few. As a rule, these models often employed phenomenological potentials (e.g., oscillator, Nilsson, Woods-Saxon, etc).…”

“…In our studies have frequently applied TGI-QRPA to investigate dipole excitations in well-deformed nuclei [2][3][4][5][6][7][8]. The main advantages of this approach include the use of a realistic mean-field potential (e.g., Woods-Saxon), the ability to account for pairing correlations, freedom from spurious effects caused by broken symmetries, and the restoration of broken translational and Galilean invariances without additional parameters for the deformed mean field [2][3][4]8].…”

“…In our studies have frequently applied TGI-QRPA to investigate dipole excitations in well-deformed nuclei [2][3][4][5][6][7][8]. The main advantages of this approach include the use of a realistic mean-field potential (e.g., Woods-Saxon), the ability to account for pairing correlations, freedom from spurious effects caused by broken symmetries, and the restoration of broken translational and Galilean invariances without additional parameters for the deformed mean field [2][3][4]8]. Using only two model parameters makes TGI-QRPA less sensitive to the model, but one of the main disadvantages of this approach is that it is not fully self-consistent, where the selfconsistency is achieved only partly through the restoration of broken translational and Galilean invariances and this could influence the obtained results.…”