Background-free inelastic scattering spectra have been obtained for 144,148,150,152,154Sm with 386 MeV α particles at forward angles (including 0°) to investigate the effect of deformation on the isoscalar giant dipole resonance. The strength distributions for isoscalar giant resonances have been extracted via a multipole decomposition analysis using angular distributions calculated in the framework of the density-dependent single-folding model. The effects of deformation are found to be different for the low- and high-excitation energy components of the isoscalar giant dipole resonance. Evidence has been obtained for the theoretically-predicted mixing between the isoscalar giant dipole resonance and the high energy octupole resonance.
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