Isoscalar giant monopole, dipole, and quadrupole resonances inZr90,92andMo92

Abstract

The isoscalar giant monopole, dipole, and quadrupole strength distributions have been deduced in 90,92 Zr, and 92 Mo from "background-free" spectra of inelastic α-particle scattering at a beam energy of 385 MeV at extremely forward angles, including 0 • . These strength distributions were extracted by a multipole-decomposition analysis based on the expected angular distributions of the respective multipoles. All these strength distributions for the three nuclei practically coincide with each other, affirming that giant resonances, being collective phenomena, are not influenced by nuclear shell structure near A ∼90, contrary to the claim in a recent measurement.

Where we stand on structure dependence of ISGMR in the Zr-Mo region: Implications on K∞

“…In the analysis of 90,92 Zr and 92 Mo in the earlier measurements [31,23], only one peak was found sufficient for the description of the ISGMR response. The parameters for the Lorentzian-distribution fits to the experimental ISGMR strength distributions are presented in Table 2.…”

“…It was argued in Refs. [31,23] that the modeling of the instrumental background could introduce some effects of this nature. Some studies have been done to ascertain the sensitivities of the giant resonance strengths to the choice of continuum in this alternative method of analysis [33].…”

“…The details of the MDA procedure employed here, as well as its suitability with regards to estimations of parameter uncertainties, are discussed in Ref. [23]. The Python implementation, emcee, for the Markov-Chain Monte-Carlo algorithm of Goodman and Weare was employed [24,25].…”

“…In 92 Mo, a different choice of optical model could increase the EWSR exhausted. Published data from Ref [23]…”

Compressional-mode resonances in the molybdenum isotopes: Emergence of softness in open-shell nuclei near A=90

“…Experimentally extracted moment ratios for 94−100 Mo calculated between 0 -35 MeV from the fit distributions of Table1. Also presented are the corresponding moment ratios from the ISGMR data of 90,92 Zr, 92 Mo[39], 112 Cd[16], 116 Sn[12,13], and 208 Pb[21] which have been re-evaluated using the distributions of Table1over this energy range.It is important to note here that while the predicted ISGMR centroid energy of 208 Pb is consistent within experimental uncertainties, the amounts by which the centroid energies of 112 Cd1 N.B. the development of deformation in 98,100 Mo causes a modest decrease in the experimentally extracted ISGMR centroid energies, which remains unaccounted for in the presented spherical RPA calculations.…”