Title: Fine structure of the isovector giant dipole resonance in ${}^{142\text{–}150}\mathrm{Nd}$ and ${}^{152}\mathrm{Sm}$

Abstract

Inelastic proton scattering at energies of a few hundred MeV and very-forward scattering angles including 0° has been established as a tool for the study of electric-dipole strength distributions in nuclei. The present work reports a systematic investigation of the chain of stable even-mass Nd isotopes representing a transition from spherical to quadrupole-deformed nuclei. Extraction of the equivalent photo-absorption cross sections and analysis of their fine structure in the energy region of the isovector giant dipole resonance (IVGDR). Method: Proton inelastic scattering reactions of 200 MeV protons were measured at the iThemba Laboratory for Accelerator Based Sciences in Cape Town, South Africa. The scattering products were momentum-analyzed by the K600 magnetic spectrometer positioned at θ_Lab = 0°. Using dispersion-matching techniques, energy resolutions of ΔE ≈ 40–50 keV (full width at half maximum) were obtained. After subtraction of background and contributions from other multipoles, the spectra were converted to photoabsorption cross sections using the equivalent virtual-photon method. Wavelet-analysis techniques are used to extract characteristic energy scales of the fine structure of the IVGDR from the experimental data. Fine structure of the IVGDR is observed even for the most deformed nuclei studied. Comparisons between the extracted experimental energy scales and those energymore » scales obtained from the quasiparticle-phonon model (QPM) and Skyrme separable random phase approximation (SSRPA) predictions provide insight into the role of different giant-resonance damping mechanisms. It can be seen that the scales in the spherical and most likely also in the deformed nuclei mainly result from the fragmentation of the one-particle-one-hole (1p1h) strength into several dominant transitions serving as doorway states. In cases where calculations beyond the 1p1h level are available, some impact of the spreading due to coupling of the two-particle-two-hole (2p2h) states to the 1p1h doorway states is observed. New virtual-photon absorption data for the chain of stable Nd isotopes and ¹⁵²Sm are presented, with a focus on the phenomenon of nonstatistical cross-section fluctuations, referred to as fine structure, in the energy region of the IVGDR. The wavelet-analysis techniques used allowed for the features of the fine structure to be quantified in the form of characteristic scales. Finally, comparisons between experimental results and model predictions indicate that Landau damping seems to be the main source of the fine structure in both the spherical and deformed nuclei, but calculations including 2p2h degrees of freedom would be beneficial to confirm this for the deformed cases.« less

Authors:

Donaldson, L. M.  ^[1];

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Carter, J. ^[2]; von Neumann-Cosel, P. ^[3]; Nesterenko, V. O. ^[4]; Neveling, R. ^[5]; Reinhard, P. -G. ^[6]; Usman, I. T. ^[2]; Adsley, P. ^[7]; Bertulani, C. A. ^[8]; Brümmer, J. W. ^[9]; Buthelezi, E. Z. ^[5]; Cooper, G. R. J. ^[2]; Fearick, R. W. ^[10]; Förtsch, S. V. ^[5]; Fujita, H. ^[11]; Fujita, Y. ^[11]; Jingo, M. ^[2]; Kheswa, N. Y. ^[5]; Kleinig, W. ^[4]; Kureba, C. O. ^[12] more »; Kvasil, J. ^[13]; Latif, M. ^[2]; Li, K. C. W. ^[9]; Mira, J. P. ^[5]; Nemulodi, F. ^[5]; Papka, P. ^[14]; Pellegri, L. ^[1]; Pietralla, N. ^[3]; Ponomarev, V. Yu. ^[3]; Rebeiro, B. ^[15]; Richter, A. ^[3]; Shirikova, N. Yu. ^[4]; Sideras-Haddad, E. ^[2]; Sushkov, A. V. ^[4]; Smit, F. D. ^[5]; Steyn, G. F. ^[5]; Swartz, J. A. ^[14]; Tamii, A. ^[11] « less

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+ Show Author Affiliations

1. iThemba LABS, Faure (South Africa); Univ. of the Witwatersrand, Johannesburg (South Africa)
2. Univ. of the Witwatersrand, Johannesburg (South Africa)
3. Technische Univ. Darmstadt (Germany). Inst. fur Kernphysik
4. Joint Inst. for Nuclear Research, Dubna (Russia). Bogoliubov Lab. of Theoretical Physics
5. iThemba LABS, Faure (South Africa)
6. Univ. Erlangen (Germany). Inst. for Theoretical Physics
7. iThemba LABS, Faure (South Africa); Univ. of the Witwatersrand, Johannesburg (South Africa); Stellenbosch Univ., Matieland (South Africa)
8. Texas A&M Univ., Commerce, TX (United States)
9. Stellenbosch Univ., Matieland (South Africa)
10. Univ. of Cape Town, Rondebosch (South Africa)
11. Osaka Univ. (Japan). Research Center for Nuclear Physics
12. Univ. of the Witwatersrand, Johannesburg (South Africa); Botswana International Univ. of Science and Technology, Palapye (Botswana)
13. Charles Univ., Prague (Czech Republic). Inst. of Particle and Nuclear Physics
14. iThemba LABS, Faure (South Africa); Stellenbosch Univ., Matieland (South Africa)
15. Univ. of the Western Cape, Cape Town (South Africa)

Publication Date:

Tue Dec 29 00:00:00 EST 2020

Research Org.:

Texas A & M Univ., Commerce, TX (United States)

Sponsoring Org.:

USDOE Office of Science (SC); National Research Foundation of South Africa; German Research Foundation (DFG); Czech Science Fondation

OSTI Identifier:

1849857

Grant/Contract Number:  

FG02-08ER41533; 85509; SFB 1245; P203-19-14048S

Resource Type:

Accepted Manuscript

Journal Name:

Physical Review. C

Additional Journal Information:

Journal Volume: 102; Journal Issue: 6; Journal ID: ISSN 2469-9985

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

73 NUCLEAR PHYSICS AND RADIATION PHYSICS; Physics; collective levels; nuclear structure & decays; resonance reactions