학술논문
Fine Structure of the Isovector Giant Dipole Resonance in $^{142-150}$Nd and $^{152}$Sm
Document Type
Working Paper
Author
Donaldson, L. M.; Carter, J.; von Neumann-Cosel, P.; Nesterenko, V. O.; Neveling, R.; Reinhard, P. -G.; Usman, I. T.; Adsley, P.; Bertulani, C. A.; Brümmer, J. W.; Buthelezi, E. Z.; Cooper, G. R. J.; Fearick, R. W.; Förtsch, S. V.; Fujita, H.; Fujita, Y.; Jingo, M.; Kheswa, N. Y.; Kleinig, W.; Kureba, C. O.; Kvasil, J.; Latif, M.; Li, K. C. W.; Mira, J. P.; Nemulodi, F.; Papka, P.; Pellegri, L.; Pietralla, N.; Ponomarev, V. Yu.; Rebeiro, B.; Richter, A.; Shirikova, N. Yu.; Sideras-Haddad, E.; Sushkov, A. V.; Smit, F. D.; Steyn, G. F.; Swartz, J. A.; Tamii, A.
Source
Phys. Rev. C 102, 064327 (2020)
Subject
Language
Abstract
Background: Inelastic proton scattering at energies of a few hundred MeV and very-forward angles including $0^\circ$ has been established as a tool to study 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. Purpose: 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 iThemba LABS in Cape Town, South Africa. The scattering products were momentum-analysed by the K600 magnetic spectrometer positioned at $\theta_{\mathrm{Lab}}=0^\circ$. Using dispersion-matching techniques, energy resolutions of $\Delta E \approx 40 - 50$ keV were obtained. After subtraction of background and contributions from other multipoles, the spectra were converted to photo-absorption cross sections using the equivalent virtual-photon method. Results: Wavelet-analysis techniques are used to extract characteristic energy scales of the fine structure of the IVGDR from the experimental data. Comparisons with the Quasiparticle-Phonon Model (QPM) and Skyrme Separable Random Phase Approximation (SSRPA) predictions provide insight into the role of different giant resonance damping mechanisms. Conclusions: Fine structure is observed even for the most deformed nuclei studied. Fragmentation of the one particle-one hole ($1p1h$) strength seems to be the main source of fine structure in both spherical and deformed nuclei. Some impact of the spreading due to coupling of the two particle-two hole ($2p2h$) states to the $1p1h$ doorway states is seen in the spherical/transitional nuclei, where calculations beyond the $1p1h$ level are available.
Comment: 17 pages, 17 figures; Minor changes made such as those clarifying the descriptions of the analysis procedure, but the results are unchanged. The current version was accepted for publication by PRC on 7 December 2020
Comment: 17 pages, 17 figures; Minor changes made such as those clarifying the descriptions of the analysis procedure, but the results are unchanged. The current version was accepted for publication by PRC on 7 December 2020