Giant Resonances in the Doubly Magic NucleusC48afrom the (e,

Abstract

The 48Ca(e,e(')n) reaction has been investigated for excitation energies 11-25 MeV and momentum transfers 0.22-0.43 fm(-1) at the superconducting Darmstadt electron linear accelerator S-DALINAC. Electric dipole and quadrupole plus monopole strength distributions are extracted from a multipole decomposition of the spectra. Their fragmented structure is described by microscopic calculations allowing for coupling of the basic particle-hole excitations to more complex configurations. Comparison of the excitation spectrum of the residual nucleus 47Ca with statistical model calculations reveals a 39(5)% contribution of direct decay to the damping of the giant dipole resonance.

Direct-decay properties of giant resonances

“…The value of 21.4%, obtained for 48 Ca, is found to be only in qualitative agreement with the corresponding experimental value of 39(5)% [2].…”

“…Direct-decay properties of GRs have been studied experimentally for a long time (see, e.g., Refs. [1][2][3][4] and references therein). To describe systematically these properties we developed a semi-microscopic approach, based on the continuum-RPA (CRPA) method and a phenomenological treatment of the spreading effect.…”

Isoscalar giant resonances inCa48

“…There is an almost Gaussian peak below 25 MeV contributing around 65% of E2 EWSR and the rest is distributed roughly uniformly between 25 and 40 MeV. The combined E0 + E2 distributions from our work are compared to the electron scattering data [16] in Fig. 7.…”

“…Strauch et al studied giant resonances in 48 Ca [16] using inelastic scattering of electrons in coincidence with neutron decay. They extracted a strength function representing the combined isoscalar giant monopole and giant quadrupole resonance strengths as well as the strength function for the isovector giant dipole resonance.…”

Semimicroscopical description of the simplest photonuclear reactions accompanied by excitation of the giant dipole resonance in medium-heavy mass nuclei

“…We make also predictions for several partial (γ, n)-reaction cross sections in the vicinity of the GDR in 208 Pb and, consequently, calculate partial direct-neutron decay branching ratios for this GR. The total branching ratio is also evaluated for the GDR in 48 Ca and compared with recent (e, e ′ n)-reaction data [13].…”