Coulomb displacement energies and decay widths of isobaric analog states from Sm(3He,t) at θ = 0°

The ^{144,147,148,149,150,154}Sm(³He, t)^{144,147,148,149,150,152,154}Eu reactions leading to ground-state isobaric analog states (IAS) have been studied at θ = 0° and E(3He) = 45.9 MeV. The Coulomb displacement energies decrease more rapidly than $\text{A}{}^{\mathrm{<mtext>?1</mtext><mtext>3</mtext>}}$. Approximately 110 keV of the total decrease of about 470 keV from A = 144 (spherical) to A = 154 (deformed) can be ascribed to deformation. No discontinuity is apparent at the transition from spherical to deformed shapes at N = 88–90. This is attributed to two effects: (i) rms radii increase with static deformations and with dynamical vibrations; (ii) Coulomb displacement energies depend on rms charge radii and on the rms radii of the neutron excess. The data suggest neutron deformations greater than proton deformations for A = 148 and 150 but smaller for A = 152 and 154. The IAS widths increase from ～30 keV to ～90 keV and can be attributed to mixing with the (T₀?1) component of a proposed isovector giant monopole resonance.