A benchmark experiment on (208)Pb shows that polarized proton inelastic scattering at very forward angles including 0° is a powerful tool for high-resolution studies of electric dipole (E1) and spin magnetic dipole (M1) modes in nuclei over a broad excitation energy range to test up-to-date nuclear models. The extracted E1 polarizability leads to a neutron skin thickness r(skin) = 0.156(-0.021)(+0.025) fm in (208)Pb derived within a mean-field model [Phys. Rev. C 81, 051303 (2010)], thereby constraining the symmetry energy and its density dependence relevant to the description of neutron stars.

High-resolution study of Gamow-Teller excitations in thê {42}Ca(^{3}He,t)^{42}Sc reaction and the observation of a "low-energy super-Gamow-Teller state"Phys. Rev. C 91, 064316

A 76 Ge( 3 He,t) 76 As charge-exchange experiment at an incident energy of 420 MeV has been performed with an energy resolution of 30 keV. The Gamow-Teller GT − strength distribution in 76 As, which is the intermediate nucleus in the double-beta (ββ) decay of 76 Ge, has been extracted. An unusually strong fragmentation of the GT − strength is observed even at low excitation energies of E x 5 MeV. By combining the data with those for GT + transitions from a recent 76 Se(d, 2 He) 76 As measurement, the nuclear matrix element for the 76 Ge 2νββ decay has been evaluated. A lack of correlation among the GT transition strengths feeding the same levels from the two different directions is observed. The impact on the 76 Ge 2νββ decay nuclear matrix element is discussed. PHYSICAL REVIEW C 86, 014304 (2012) 76 Ge 76 As 76 Se 2 − 1 + 1 + 1 + 0 + 0 + β − β − 44.425(1) keV 86.787(1) keV 120.258(1) keV Q β − β − = 2039.00(5) keV Q β − = 2962 keV Q EC = 923 keV J π =1 +

Gamow-Teller (GT) transitions in atomic nuclei are sensitive to both nuclear shell structure and effective residual interactions. The nuclear GT excitations were studied for the mass number A ¼ 42, 46, 50, and 54 "f-shell" nuclei in ( 3 He, t) charge-exchange reactions. In the 42 Ca → 42 Sc reaction, most of the GT strength is concentrated in the lowest excited state at 0.6 MeV, suggesting the existence of a low-energy GT phonon excitation. As A increases, a high-energy GT phonon excitation develops in the 6-11 MeV region. In the 54 Fe → 54 Co reaction, the high-energy GT phonon excitation mainly carries the GT strength. The existence of these two GT phonon excitations are attributed to the 2 fermionic degrees of freedom in nuclei.