Low-energy dipole strength and the critical case of 48Ca

摘要: Abstract Recent theoretical work has not led to a consensus regarding the nature of low-energy E1 strength in 40,44,48 Ca isotopes, for which high-resolution ( γ , ′ ) data exist. Here we revisit this problem using first-order quasiparticle random-phase approximation (QRPA) and different interactions. First examine all even isotopes with N = 14 – 40 . All are predicted undergo dipole transitions at low energy, large comparable isoscalar but varying strength. Provided moderate uniform energetic shift is introduced results, QRPA Gogny D1S interaction able account data, because, up 28 it yields rather pure oscillation. A neutron-skin oscillation anticipated ⩾ 30 This contradicts existing predictions that 44,48 develop mode. Which result correct cannot be resolved conclusively available data. We propose alpha-scattering, possibly followed by an electroexcitation experiment, could resolve situation thereby help improve models aspiring describe reliably nuclei.