[en] Complete text of publication follows. Recently, a strong movement of the single particle states in neutron rich O and C isotopes has been revealed, which resulted in N=14,16 subshell closures in the oxygen isotopes. As a consequence, a close lying doublet of neutron s_1/2 and d_5/2 states is expected along the whole C isotopic chain. In order to reveal this possibility, we studied the structure of the neutron-rich nuclei ^17,19C using fragmentation reactions of radioactive beams. Based on particle-γ and particle-γγ coincidence data, level schemes were constructed for the studied nuclei. The γ-ray spectrum of the odd nucleus ¹⁷C exhibits two transitions (see figure 1). The relative intensity is the same in the γ-ray spectra of ¹⁷C obtained from the low and high γ-ray multiplicity events. This indicates that the two transitions correspond to the decay of two excited states at 207 and 329 keV directly to the ground state. The ¹⁷C ground state has a 3/2⁺ spin value. From the ¹⁷C(p,p') study a tentative spin 1/2⁺ was assigned to the lower energy excited state and a spin 5/2⁺ to the higher energy one. The proposed level scheme, shown in figure 2, is in a reasonable agreement with shell model calculations. For ¹⁹C a 1/2⁺ configuration have been proposed for the ground state. As the 201-keV γ-transition is observed in our work as a prompt radiation, it should connect states separated by small spin differences such as 3/2⁺ → 1/2⁺. Shell-model calculations predict the existence of three low-lying states with spins 1/2⁺, 3/2⁺, and 5/2⁺ within a few hundred keV (see figure 2). In the Riken (p,p') experiment the 5/2⁺ has been found 72 keV above the 3/2⁺ one. Thus, both in ¹⁷C and ¹⁹C the 1/2⁺ and 5/2⁺ states are a few hundred keV away

[en] The breakup of a halo nuclei from a stable nucleus is a sensitive tool of the reaction framework. In order to study the halo continuum, both resonant and nonresonant contributions should be taken into account. In addition a proper treatment of the few-body dynamics of the three-body problem should be accomplished in case only few degrees of freedom play a role in the reaction mechanism. Most recently, the Faddeev/AGS multiple scattering reaction formalism [1,2,3] has been applied to the study of reactions involving two-body halo nuclei [4,5,6]. These works have shown that a tighter control in the reaction theory is needed and that traditional reaction approaches may not be adequate to interpret and extract accurate and reliable structure information from the data. Our aim is to use the Faddeev/AGS scattering approach to analyse the experimental data, which unlike other approximate reaction methods provides a numerically exact solution of the underlying effective three-body Hamiltonian. We calculate inclusive breakup angular cross sections and energy spectrum observables for the scattering of one neutron-halo nuclei 1^1Be and 1^9C from a proton target at intermediate energies and compare with existing experimental data [7,8] respectively.(author)

[en] Three-dimensional (3D) seismic-reflection analysis of a major Miocene-to-Pleistocene (c. 19–2 Ma) clinoform succession of the central Taranaki Basin offshore New Zealand reveals two distinct intervals of downbuilding progradation (c. 7.5–6 Ma; and c. 4–2 Ma). Downbuilding clinoforms are of kilometre scale and characterized by straight upper foreset gullies that initiate near or at the clinoform breakpoint, in places connected to topset distributary channels. Foreset mass-transport complexes occur mainly in the basal parts of downbuilding clinoform successions. Upbuilding progradational clinoforms formed between c. 6–5.5 Ma and c. 4.5–4 Ma. These clinoforms are generally smaller, with topsets in places comprising beach ridges and tidal channels. The foresets of the upbuilding clinoforms contain large gullies and sinuous deepwater channels, locally connected to topset channels. Retrogradational deposits in the studied succession (c. 5.5–4.5 Ma) lack a distinct clinoform geometry, show a few slope channels and gullies, and are characterized by extensive landward-stepping networks of shallow-marine and fluvial channels. 3D seismic-reflection analysis of the c. 2000 km² study area allows an exemplary 3D documentation of migrating depositional systems along a highly progradational clastic margin, constrained by a stratigraphic framework tightly defined by the two intervals of major depositional downbuilding. The Late Miocene downbuilding is interpreted as forced by tectonic uplift along the Cape Egmont fault and neighbouring structures in the south of the study area. In contrast, the Plio-Pleistocene downbuilding is interpreted as dominantly controlled by eustasy in a tectonic environment characterized by subsidence. Excellent preservation of the 4–2 Ma clinoform topsets provides unique insights into depositional systems at and above the shelf break imaging palaeo-shoreline and palaeo-backshore environments. The detailed 3D clinoform analyses presented contribute to the understanding of clastic sedimentation processes from shelf to slope, which can be used to predict deepwater depositional facies.

[en] Change of shell closures far from stability are discussed. The effect of orbital changes and anomalies around N=16 shell closure is discussed with examples of ²³O and ¹⁹C

[en] In recent times, the stripping reactions measuring the longitudinal momentum distribution and absorption cross section have been used as a prolific tool to investigate the ground state properties of neutron rich nuclei. The nuclei ¹¹Be and ¹⁹C, being paradigm for single neutron halo, have attracted a significant interest, both theoretically as well as experimentally

[en] The extremely neutron-rich nucleus ¹⁹C has attracted much attention for its exotic properties. The most interesting is that the ground state of ¹⁹C behaves like a one-neutron halo. In order to understand this peculiar characteristic, we apply the complex momentum representation method to explore the weakly bound structure of ¹⁹C. We have calculated the single-particle energies for the bound and resonant states together with their evolutions to deformation, and checked the occupation probabilities of major configurations in the level occupied by the valance neutron. The result suggests that ¹⁹C is a prolate halo formed by a dominant s-wave configuration. (paper)

[en] The units of the ordinate axis of Fig. 2 on page 506 were given incorrectly as [mb/(GeV/c)]. They should be [mb/(MeV/c)]. This change does not affect any of the results in Table 1, including the cross sections, nor the subsequent discussion. (authors)

[en] We show that under certain conditions a simple relationship exists between the elastic scattering of a composite halo nucleus and of its core from a stable target. The coupling of the elastic and projectile excitation channels is crucial to the analysis, which is particularly useful when the ratio of the halo to the core mass is small. In the case of ¹¹Be elastic scattering the cross section relationship is quite well satisfied. For both ¹¹Be and ¹⁹C our analysis reveals a significant sensitivity of elastic scattering data to the halo size and structure. copyright 1997 The American Physical Society

[en] Complete text of publication follows. Theoretical calculations predict two low-lying excited states of both ¹⁷C and ¹⁹C, but only one excited state has been found in ¹⁷C. Recently, indications of two γ transitions of ¹⁷C have been reported, suggesting that both predicted excited states are bound in ¹⁷C. In addition, a γ peak in ¹⁹C was also observed. To obtain more information on the excited states in neutron rich odd carbon nuclei we have studied them by the (p,p'γ) process in inverse kinematics. The experiment was carried out at the RIKEN radioactive isotope separator RIPS. A ²²Ne primary beam of 100 pnA intensity and 110 A x MeV energy hits a ⁹Be production target of 0.8 cm thickness. For optimizing the ¹⁹C beam, the secondary cocktail beam included 20% ¹⁹C and 25% ¹⁷B. By tuning the ¹⁷C beam, practically 100% purity could be achieved. On an event-by-event basis, the identification of the incoming beam was performed by energy-loss, time-of-fight (TOF) and magnetic rigidity (Bρ) measurements. The secondary beam bombarded a liquid hydrogen target of 3 cm diameter. A NaI(Tl) array surrounded the liquid hydrogen target to detect de-excited γ rays. A silicon telescope with layers of 0.5, 2 and 2 mm thicknesses was inserted in air atmosphere to identify scattered particles. To produce γ ray spectra, one fold events in the NaI(Tl) setup were selected (Fig. 1). In the (a) panel, two peaks are clearly visible at 72(4) and 197(6) keV which can be associated with the prompt decays of excited states of ¹⁹C. Fig. 1 shows two distinct peaks at 210(4) and 331(6) keV confirming two low-lying excited states of ¹⁷C. In the panel of the ¹H(¹⁷C,¹⁷C) reaction, the higher energy peak is clearly visible, while the 210 keV peak is very faint, if it exists at all, and is situated on the Compton background of the 331 keV peak. The counting statistics in Fig. 1 allowed us to perform a γ-γ coincidence analysis, which showed that the two observed transitions of ¹⁷C are not in coincidence. The analyses of the spectra and the cross sections are now in progress. (author)

[en] The availability of radioactive ion beams has made it possible to investigate the properties of nuclei lying in the close proximity of neutron and proton drip lines. The pioneering experiments performed by I. Tanihata and collaborators using beams of highly neutron rich nuclei have confirmed the existence of a novel halo structure among some of these isotopes