A. Shevchenko

Fine structure of the isoscalar giant quadrupole resonance in 40Ca due to Landau damping

Abstract The fragmentation of the Isoscalar Giant Quadrupole Resonance (ISGQR) in 40Ca has been investigated in high energy-resolution experiments using proton inelastic scattering at E p = 200 MeV . Fine structure is observed in the region of the ISGQR and its characteristic energy scales are extracted from the experimental data by means of a wavelet analysis. The experimental scales are well described by Random Phase Approximation (RPA) and second-RPA calculations with an effective interaction derived from a realistic nucleon–nucleon interaction by the Unitary Correlation Operator Method (UCOM). In these results characteristic scales are already present at the mean-field level pointing to their origination in Landau damping, in contrast to the findings in heavier nuclei and also to SRPA calculations for 40Ca based on phenomenological effective interactions, where fine structure is explained by the coupling to two-particle–two-hole (2p–2h) states.

Distribution of the GT strength starting from the ground state of 14N

Two charge‐exchange reactions were performed at intermediate energies in order to investigate the Gamow‐Teller strength distribution starting from 14Ng.s. in β+ and β− directions: 14N(d,2He)14C and 14N(3He,t)14O. We describe here a few delicate details of the experimental techniques used in these investigations.

Magnetic Dipole and Gamow‐Teller Modes in Neutrino‐Nucleus Reactions: Impact on Supernova Dynamics and Nucleosynthesis

Some aspects of the importance of neutrino‐induced reactions on nuclei within supernova physics are discussed. It is argued that important constraints on the experimentally unknown cross sections can be obtained from experimental studies of the nuclear response in selected cases. Examples are neutral‐current induced reactions on fp‐shell nuclei extracted from high‐resolution inelastic electron scattering data providing the M1 strength distributions and the production of the exotic heavy, odd‐odd nuclei 138La and 180Ta through charged‐current reactions dominated by Gamow‐Teller transitions. The Gamow‐Teller strength can deduced from the (3He,t) charge‐exchange reaction at zero degree.

Spin‐isospin excitations from the ground‐state of 64Ni

Spin‐isospin (Gamow‐Teller) excitations in 64Cu and 64Co have been studied using (3He,t) and (d,2He) charge‐exchange reactions on 64Ni. As the isospin of the 64Ni ground‐state is T0=4, states with T=3, 4 and 5 in 64Cu are excited via the (3He,t) reaction and states with T=5 in 64Co via (d,2He). If we assume that the nuclear interaction is charge symmetric, the T=5 states in 64Cu should appear at corresponding excitation energies (if corrected for the Coulomb displacement) and with similar strengths as the T=5 states in 64Co. As in the 64Cu spectrum the T=5 states are very weakly excited, only by combining the results of the two complementary experiments one can estimate the Gamow‐Teller strength starting from 64Ni in a consistent way.

Structure of 7He studied with the 7Li(d,2He) reaction

A search for the Jπ = 1/2− spin–orbit partner of the Jπ = 3/2− ground state in 7He has been performed with the 7Li(d,2He) charge-exchange reaction. The results are incompatible with recent claims of such a state at very low excitation energy [Meister M et al 2002 Phys. Rev. Lett. 88 102501] but rather suggest a resonance with parameters Ex = (1.2+0.5 −0.4) MeV, Λ = (1.9+0.8−0.4) MeV. GT strengths deduced for the transitions to the lowest states in 7He are in remarkable agreement with ab initio quantum Monte Carlo calculations.

Study of Gamow‐Teller Transition Strengths in fp‐shell Nuclei Using the 64Ni(d,2He)64Co Reaction

The 64Ni(d,2He)64Co reaction was studied at the AGOR cyclotron of the KVI, Groningen, with the Big‐Bite Spectrometer and the EuroSuperNova detector using a deuteron beam of 170 MeV. An energy resolution of about 100 keV was achieved. In addition to the ground‐state with Jπ = 1+, several other 1+ states could be identified and the strengths of the corresponding Gamow‐Teller transitions determined.