We present the giant electric-dipole and electric-quadrupole cross sections of ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ca}$ and ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ca}$ measured by inelastic electron scattering with incident energies between 124 and 250 MeV. Spectra were decomposed into dipole, quadrupole, and other higher multipole components. The giant dipole resonances in both nuclei have a large width of approximately 12 MeV, with at least two gross resonance structures. The quadrupole resonances are distributed in several clusters between 10 and 22 MeV, depleting (61±9)% in ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ca}$ and (46±7)% in ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ca}$ of the isoscalar energy-weighted sum rule, respectively. Higher multipole resonances were also found in the same excitation energy region. The observed structure in the dipole and quadrupole resonances are examined in terms of the collective model, and it is suggested that the splitting of the dipole resonance revealed in ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ca}$ may reflect the effect of nuclear deformation.

NUCLEAR REACTIONS ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ca}$ ($e$,$e^{\prime }$) and ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ca}$ ($e$,$e^{\prime }$), $E=124\mathrm{}\sim 250$ MeV, $q=0.4\mathrm{}\sim 1.2$ fm${}_{}{}^{-1\mathrm{}}{}_{}{}^{},\mathrm{e}\mathrm{n}\mathrm{r}\mathrm{i}\mathrm{c}\mathrm{h}\mathrm{e}\mathrm{d}$ target, measured $\sigma (E^{\prime },\theta )$ up to 35 MeV in excitation energy; deduced electric-dipole, electric-quadrupole, and higher multipole strength in the giant resonance region.

• Received 18 February 1981

DOI:https://doi.org/10.1103/PhysRevC.24.1969