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Register a new userRole of cross-shell excitations in the reaction 54Fe(d_pol,p)55Fe
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The reaction 54Fe(d_pol,p)55Fe was studied at the Munich Q3D spectrograph with a 14 MeV polarized deuteron beam. Excitation energies, angular distributions and analyzing powers were measured for 39 states up to 4.5 MeV excitation energy. Spin and parity assignments were made and spectroscopic factors deduced by comparison to DWBA calculations. The results were compared to predictions by large scale shell model calculations in the full pf-shell and it was found that reasonable agreement for energies and spectroscopic factors below 2.5 MeV could only be obtained if up to 6 particles were allowed to be excited from the f_7/2 orbital into p_3/2, f_5/2, and p_1/2 orbitals across the N=28 gap. For levels above 2.5 MeV the experimental strength distribution was found to be significantly more fragmented than predicted by the shell model calculations.
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The neutron-rich Ni isotopes have attracted attention in recent years due to the occurrence of shape or configuration coexistence. We report on the difference in population of excited final states in 70Ni following gamma-ray tagged one-proton, one-neutron, and two-proton knockout from 71Cu, 71Ni, and 72Zn rare-isotope beams, respectively. Using variations observed in the relative transition intensities, signaling the changed population of specific final states in the different reactions, the role of neutron and proton configurations in excited states of 70Ni is probed schematically, with the goal of identifying those that carry, as leading configuration, proton excitations across the Z = 28 shell closure. Such states are suggested in the literature to form a collective structure associated with prolate deformation. Adding to the body of knowledge for 70Ni, 29 new transitions are reported, of which 15 are placed in its level scheme.
Excited states in $^{20}$O were populated in the reaction $^{10}$Be($^{14}$C,$alpha$) at Florida State University. Charged particles were detected with a particle telescope consisting of 4 annularly segmented Si surface barrier detectors and $gamma$ radiation was detected with the FSU $gamma$ detector array. Five new states were observed below 6 MeV from the $alpha$-$gamma$ and $alpha$-$gamma$-$gamma$ coincidence data. Shell model calculations suggest that most of the newly observed states are core-excited 1p-1h excitations across the $N = Z = 8$ shell gap. Comparisons between experimental data and calculations for the neutron-rich O and F isotopes imply a steady reduction of the $p$-$sd$ shell gap as neutrons are added.
The transfer of neutrons onto 24Ne has been measured using a reaccelerated radioactive beam of 24Ne to study the (d,p) reaction in inverse kinematics. The unusual raising of the first 3/2+ level in 25Ne and its significance in terms of the migration of the neutron magic number from N=20 to N=16 is put on a firm footing by confirmation of this states identity. The raised 3/2+ level is observed simultaneously with the intruder negative parity 7/2- and 3/2- levels, providing evidence for the reduction in the N=20 gap. The coincident gamma-ray decays allowed the assignment of spins as well as the transferred orbital angular momentum. The excitation energy of the 3/2+ state shows that the established USD shell model breaks down well within the sd model space and requires a revised treatment of the proton-neutron monopole interaction.
This letter is concerned with the study of the $K^-_{stop}Arightarrow pi^pmSigma^mp A$ reaction in p-shell nuclei, i.e., $^{6,7}Li$, $^9Be$, $^{13}C$ and $^{16}O$. The $pi^pmSigma^mp / K^-_{stop}$ emission rates are reported as a function of $A$. These rates are discussed in comparison with previous findings. The ratio $pi^-Sigma^+/pi^+Sigma^-$ in p-shell nuclei is found to depart largely from that on hydrogen, which provides support for large in-medium effects possibly generated by the sub-threshold $Lambda(1405)$. The continuum momentum spectra of prompt pions and free sigmas are also discussed as well as the $pi^pmSigma^mp$ missing mass behavior and the link with the reaction mechanism. The apparatus used for the investigation is the FINUDA spectrometer operating at the DA$Phi$NE $phi$-factory (LNF-INFN, Italy).
The interpretation of the most recent solar neutrinos experiments requires a good knowledge of the cross section of the reaction 7Be(p,gamma)8B at very small energy (Ecm=18 keV). We have recently measured this cross section for Ecm=0.35-1.4 MeV and for Ecm=0.112-0.190 MeV. We report here on the description of the preparation of the radioactive targets of 7Be used in these experiments.
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