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7 pags., 5 figs., The proton drip-line nucleus 17Ne is investigated experimentally in order to determine its two-proton halo character. A fully exclusive measurement of the 17Ne(p,2p)16F->15O+p quasi-free one-proton knockout reaction has been performed at GSI at around 500 MeV/nucleon beam energy. All particles resulting from the scattering process have been detected. The relevant reconstructed quantities are the angles of the two protons scattered in quasi-elastic kinematics, the decay of 16F into 15O (including gamma decays from excited states) and a proton, as well as the 15O+p relative-energy spectrum and the 16F momentum distributions. The latter two quantities allow an independent and consistent determination of the ratio of l=0 and l=2 motion of the valence protons in 17Ne. With a resulting relatively small l=0 component of only around 35(3)%, it is concluded that 17Ne exhibits a rather modest halo character only. The quantitative agreement of the two values deduced from the energy spectrum and the momentum distributions supports the theoretical treatment of the calculation of momentum distributions after quasi-free knockout reactions at high energies by taking into account distortions based on the Glauber theory. Moreover, the experimental data allow the separation of valence-proton knockout and knockout from the 15O core. The latter process contributes with 11.8(3.1) mb around 40% to the total proton-knockout cross section of 30.3(2.3) mb, which explains previously reported contradicting conclusions derived from inclusive cross sections., This work is supported by the German Federal Ministry for Education and Research (BMBF) under contract No. 05P15RDFN1, the ExtreMe Matter Institute (EMMI), HIC for FAIR, and the GSI- TU Darmstadt cooperation agreement. Financial support from the Swedish Research Council, from the Russian Foundation for Ba- sic Research (RFBR Grant 12-02-01115-a), and from the Spanish grants from MICINN AEI FPA2017-87568-P, PGC2018-0099746-B- C21, FPA2015-64969-P, PID2019-104390GB-I00, RTI2018-098868- B-100, and Maria de Maeztu Units of excellence MDM-2016-0692 are also acknowledged. One of us (B. J.) is a Helmholtz Interna- tional Fellow. C.A.B. acknowledges support by the U.S. DOE grant DE-FG02-08ER41533 and the U.S. NSF Grant No. 1415656

The surface excitation spectra of the B-terminated and Mg-terminated MgB(0001) surfaces are studied in the ab initio time-dependent density functional theory approach. The band structure of both these surfaces is fully included into evaluation of the surface response function using a linear response approach. We find that different surface electronic structures for these surface terminations result in very different surface collective electronic excitations. Due to a number of surface states and peculiarity of the MgB dielectric properties several surface plasmons, such as surface plasmon, interband surface plasmon, acoustic surface plasmon, and others have been found. We trace their evolution with momentum transfer change on both surfaces. Whereas at vanishing momentum transfers the plasmons in both systems can be understood considering the bulk MgB dielectric function, upon momentum increase the collective excitations present very different behavior. We relay such behavior to the differences in the surface electronic structure of the studied terminations., V.M.S. and E.V.C. acknowledge the partial support from the Spanish Ministry of Economy and Competitiveness MINECO, Grant Nos. FIS2016-76617-P and FIS2016-75862-P. V.M.S acknowledges project PI2017-30 of the Departamento de Educación, Política Lingüística y Cultura of the Basque government. E.V.C. acknowledges support of the Tomsk State University Academic D.I. Mendeleev Fund Program (Grant No. 8.1.01.2017) and Saint Petersburg State University (Project 15.61.202.2015).

36 pages, 10 figures, 8 tables, 3 appendices.-- PACS nrs.: 27.20.+n; 24.70.+s.-- Printed version published Jul 15, 2007., Fragmentation reactions in a carbon target with beams of Li-11 and Be-14 at relativistic energies have been studied in a kinematically complete experiment at the ALADIN-LAND setup at GSI. Excited states in Li-11 and Be-14 were obtained from the data in the inelastic channel. The measured cross sections with the core nucleus in the final state show that in the Be-14 case core polarization plays an important role. In the one-neutron knockout channels the measured angular correlations between fragment and neutron are asymmetric, which demonstrates the presence of states with different parities in the Li-11 and Be-14 ground states. For Li-10 a low-lying virtual s-state, a p-state and evidence for a d-state could be extracted from the data, while the Be-12 + n system shows resonances with more complicated structure., This work was supported by the BMBF under Contracts No. 06 DA 115, No. 06 OF 838 and No. 06 MZ 864 I and by GSI via Hochschulzusammenarbeitsvereinbarungen under Contracts No. DA RICK, No. OF ELZ, No. MZ KRAK and partly supported by the Polish Committee of Scientific Research under Contract No. KBN/2P03B/144/10, CICYT under Contract No. FPA2005-02379 (MJGB, OT), RFBR under Contract No. 04-02-17251, EC under Contract No. ERBCHGE-CT92-0003, and under the auspices of the US Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No.W-7405-Eng-48. One of us (T.N.) is a Royal Swedish Academy of Sciences Research Fellow supported by a grant from the Knut and Alice Wallenberg Foundation.

4 pages, 4 figures, 1 table.-- PACS nrs.: 25.60.Gc, 25.60.Dz, 27.20.+n., Breakup reactions were used to study the ground-state configuration of the neutron-rich isotope O-23. The O-22 fragments produced in one-nucleon removal from O-23 at 938 MeV/nucleon in a carbon target were detected in coincidence with de-exciting γ rays, allowing to discern between 220 ground-state and excited-states contributions. From the comparison of exclusive experimental momentum distributions for the one-neutron removal channel to theoretical momentum distributions calculated in an Eikonal model for the knockout process, and spin and parity assignment of I-π = 1/2(+) was deduced for the 230 ground state. This result solved the existent experimental discrepancy.

14 pages, 6 figures.-- PACS nrs.: 27.20.+n; 24.70.+. Dissociation of a 240 MeV/u beam of He-6, incident on carbon and lead targets, has been studied in kinematically complete experiments to investigate low-lying excitation modes in the halo nucleus He-6. It is shown that alignment effects characterize the inelastic scattering and allow an unambiguous assignment of the spin of a narrow resonance observed in the excitation energy spectrum. The differential cross sections for the He-6 inelastic scattering on carbon and lead targets were deduced from the measured moments of the two neutrons and the a-particle. An analysis of these distributions shows that quadrupole and, possibly, monopole excitations characterize the hadronic interaction, while the dipole mode is dominating in Coulomb dissociation. Neither theoretically predicted new resonance states in He-6 nor nuclear excitation of a dipole mode were found. Direct evidence has been obtained for strong suppression of Coulornb post-acceleration in direct Coulomb breakup in a lead target. This work was supported by the BMBF under Contracts 06 DA 820, 06 OF 112 and 06 MZ 864 and by GSI via Hochschulzusammenarbeitsvereinbarungen under Contracts DA RICK, OF ELZ, MZ KRK and partly supported by the Polish Committee of Scientific Research under Contract PBZ/PB03/113/09, EC under contract ER-BCHGE-CT92-0003, CICYT under contract AEN92-0788-C02-02 MJGB.and WTZ under contract RUS 609-96. One of us (B.J.) acknowledges the support through an Alexander von Humboldt Research Award.

26 pages, 5 tables, 10 figures.-- PACS nrs.: 25.60.+v; 27.20.+n; 25.70.Mn; 25.70.De., Break-up of secondary Li-11 ion beams (280 MeV/nucleon) on C and Pb targets into Li-9 and neutrons is studied experimentally. Cross sections and neutron multiplicity distributions are obtained, characterizing different reaction mechanisms. Invariant-mass spectroscopy for Li-11 and Li-10 is performed. The E1 strength distribution, deduced from electromagnetic excitation of Li-11 up to an excitation energy of 4 MeV comprises ~8% of the Thomas-Reiche-Kuhn energy-weighted sumrule strength. Two low-lying resonance-like structures are observed for Li-10 at decay energies of 0.21(5) and 0.62(10) MeV, the former one carrying 26(10)% of the strength and likely to be associated with an s-wave neutron decay. A strong di-neutron correlation in Li-11 can be discarded. Calculations in a quasi-particle RPA approach are compared with the experimental results for Li-10 and Li-11., The authors are indebted to the staff personel of the GSI accelerator group and of the target laboratory for their support. We acknowledge support by the German Federal Minister for Research and Technology (BMBF) under Contracts 06DA 665 I, 06OF 112 and 06MZ 465, by GSI under Contracts DA RIK, OF ELZ, MZ KRK, by the Polish Committee of Scientific Research under Contract PBZ/PB03 / 113/09, EC under contract ERBCHGE-CT92-0003 and by the Spanish CICYT under contract AEN92-0788-C02-02(MJGB).

4 pages, 2 figures.-- PACS nrs.: 25.60.Gc, 24.70.+s, 27.10.+h., Peripheral fragmentation of a 240 MeV/nucleon beam of the halo nucleus He-6 incident on carbon target has been studied in a kinematically complete experiment. It is found that one-neutron stripping to the unbound nucleus He-5 is the dominant fragmentation mechanism and that it leads to a spin alignment of He-5 in a plane perpendicular to the He-5 momentum vector. This is expected to be a common feature for all neutron halo nuclei., This work was supported by the BMBF under Contracts No. 06 DA 665 I, No. 06 OF 112, and No. 06 MZ 465 and by GSI via Hochschulzusammenarbeitsvereinbarungen under Contracts No. DA RICK, No. OF ELZ, and No. MZ KRK, as well as partly supported by the Polish Committee of Scientific Research under Contract No. PBZyPB03y113y09, EC under Contract No. ERBCHGE-CT92-0003, and CICYT under Contract No. AEN92-0788-C02-02 (MJGB).

Low-lying resonance state in 7He(6He + n) which was formed after fragmentation reactions of a 227 MeV/nucleon 8He beam on a carbon target was investigated. The produced nuclei was separated using the fragment separator (FRS) before interacting with a 1.3 g/cm2 carbon target. The result shows that the relative energy spectrum in the 6He + n system shows a structure as the 7He ground state unbounded with 0.43(2) MeV with respect to the 6He + n system and having a width of γ = 0.15(8) MeV overlapping with an excited state observed at 1.0(1) MeV with a width of γ = 0.75(8) MeV.