Nuclear Physics and Atomic Energy

ядерна ф≥зика та енергетика
Nuclear Physics and Atomic Energy

  ISSN: 1818-331X (Print), 2074-0565 (Online)
  Publisher: Institute for Nuclear Research of the National Academy of Sciences of Ukraine
  Languages: Ukrainian, English, Russian
  Periodicity: 4 times per year

  Open access peer reviewed journal


 Home page   About 
Nucl. Phys. At. Energy 2020, volume 21, issue 2, pages 129-136.
Section: Nuclear Physics.
Received: 28.11.2019; Accepted: 19.03.2020; Published online: 3.09.2020.
PDF Full text (en)
https://doi.org/10.15407/jnpae2020.02.129

Isoscalar dipole response of heavy nuclei in low-energy region within kinetic model

V. I. Abrosimov*, O. I. Davydovska

Institute for Nuclear Research, National Academy of Sciences of Ukraine, Kyiv, Ukraine

*Corresponding author. E-mail address: abrosim@kinr.kiev.ua

Abstract: The isoscalar dipole response of heavy spherical nuclei in the low-energy region is studied by using a semiclassical model, based on the solution of the linearized Vlasov kinetic equation for finite Fermi systems. In this translation-invariant model, the excitations of the center of mass motion are exactly separated from the internal ones. The isoscalar dipole strength function displays three resonance structures in the energy region up to 15 MeV. Calculations of the velocity fields associated with resonance structures at centroid energies show the vortex (toroidal) nature of two overlying resonances. The main toroidal resonance gives a qualitative description of the low-energy isoscalar dipole resonance, which is observed in heavy spherical nuclei. The origin of the lowest isoscalar dipole resonance structure is apparently related to dipole single-particle excitations. Its centroid energy is close to the minimum energy of the dipole single-particle spectrum, and taking into account the residual interaction leads only to an insignificant shift of the centroid energy towards lower energy. However, the inclusion of residual interaction noticeably enhances the velocity field associated with the lowest resonance, which indicates collective effects in this resonance structure.

Keywords: kinetic model, low-energy resonance structures, velocity field, toroidal resonances.

References:

1. H.L. Clark, Y.-W. Lui, D.H. Youngblood. Isoscalar giant dipole resonance in 90Zr, 116Sn, and 208Pb. Phys. Rev. C 63 (2001) 031301. https://doi.org/10.1103/PhysRevC.63.031301

2. D.H. Youngblood et al. Isoscalar E0 - E3 strength in 166Sn, 144Sm, 154Sm, and 208Pb. Phys. Rev. C 69 (2004) 034315. https://doi.org/10.1103/PhysRevC.69.034315

3. M. Uchida et al. Isoscalar giant dipole resonance in 208Pb via inelastic alpha scattering at 400 MeV and nuclear incompressibility. Phys. Lett. B 557 (2003) 12. https://doi.org/10.1016/S0370-2693(03)00137-0

4. M. Uchida et al. Systematics of the bimodal isoscalar giant dipole resonance. Phys. Rev. C 69 (2004) 051301(R). https://doi.org/10.1103/PhysRevC.69.051301

5. D. Vretenar, A. Wandelt and P. Ring. Isoscalar dipole mode in relativistic random phase approximation. Phys. Lett. B 487 (2000) 334. https://doi.org/10.1016/S0370-2693(00)00827-3

6. G. Colo et al. On dipole compression modes in nuclei. Phys. Lett. B 485 (2000) 362. https://doi.org/10.1016/S0370-2693(00)00725-5

7. M.L. Gorelik, M.H. Urin. Properties of the isoscalar giant dipole resonance Phys. Rev. C 64 (2001) 047301. https://doi.org/10.1103/PhysRevC.64.047301

8. D. Vretenar et al. Toroidal dipole resonances in the relativistic random phase approximation. Phys. Rev. C 65 (2002) 021301(R). https://doi.org/10.1103/PhysRevC.65.021301

9. J. Kvasil et al. Compressional and toroidal dipole modes in nuclei. J. Phys. G: Nucl. Part. Phys. 29 (2003) 753. https://doi.org/10.1088/0954-3899/29/4/312

10. A. Repko et al. Toroidal nature of the low-energy E1 mode. Phys. Rev. C 87 (2013) 024305. https://doi.org/10.1103/PhysRevC.87.024305

11. P.-G. Reinhard et al. Nuclear vorticity in isoscalar E1 modes: Skyrme-random-phase approximation analysis. Phys. Rev. C 89 (2014) 024321. https://doi.org/10.1103/PhysRevC.89.024321

12. Yoshiko Kanada-En'yo, Yuki Shikata. Toroidal, compressive, and E1 properties of low-energy dipole modes in 10Be. Phys. Rev. C 95 (2017) 064319. https://doi.org/10.1103/PhysRevC.95.064319

13. V.O. Nesterenko et al. Individual Low-Energy Toroidal Dipole State in 24Mg. Phys. Rev. Lett. 120 (2018) 182501. https://doi.org/10.1103/PhysRevLett.120.182501

14. A. Repko et al. Systematics of toroidal dipole modes in Ca, Ni, Zr, and Sn isotopes. Eur. Phys. J. A 55 (2019) 242. https://doi.org/10.1140/epja/i2019-12770-x

15. A. Repko, J. Kvasil, V.O. Nesterenko. Elimination of spurious modes within quasiparticle random-phase approximation. Phys. Rev. C 99 (2019) 044307. https://doi.org/10.1103/PhysRevC.99.044307

16. E.B. Balbutsev, I.V. Molodtsova, A.V. Unzhakova. Compressional and toroidal dipole excitations of atomic nuclei. Europhys. Lett. 26 (1994) 499. https://doi.org/10.1209/0295-5075/26/7/004

17. V.I. Abrosimov, A. Dellafiore, F. Matera. Kinetic-theory description of isoscalar dipole modes. Nucl. Phys. A 697 (2002) 748. https://doi.org/10.1016/S0375-9474(01)01273-8

18. M. Urban. Pygmy resonance and torus mode within Vlasov dynamics. Phys. Rev. C 85 (2012) 034322. https://doi.org/10.1103/PhysRevC.85.034322

19. V.I. Abrosimov, O.I. Davydovska. Residual interaction effect on isoscalar dipole modes in heavy nuclei. Ukr. J. Phys. 61 (2016) 571. https://doi.org/10.15407/ujpe61.07.0565

20. V.I. Abrosimov, O.I. Davydovska. Nature of isoscalar dipole resonances in heavy nuclei. Ukr. J. Phys. 63 (2018) 1043. https://doi.org/10.15407/ujpe63.12.1043

21. V.I. Abrosimov, A. Dellafiore, F. Matera. Collective motion in finite Fermi systems within Vlasov dynamics. Phys. Part. Nucl. 36 (2005) 699. http://www1.jinr.ru/Pepan/2005-v36/v-36-6/pdf/v-36-6_02.pdf

22. I. Hamamoto, H. Sagawa, X.Z. Zhang. Displacement fields of excited states in stable and neutron drip-line nuclei. Nucl. Phys. A 648 (1999) 203. https://doi.org/10.1016/S0375-9474(99)00024-X

23. E. Lipparini, S. Stringari. Sum rules and giant resonances in nuclei. Phys. Rep. 175 (1989) 103. https://doi.org/10.1016/0370-1573(89)90029-X