Deep excursion beyond the proton dripline. I. Argon and chlorine isotope chains

The proton-unbound argon and chlorine isotopes have been studied by measuring trajectories of their decay-in-flight products by using a tracking technique with microstrip detectors. The proton (1p) and two-proton (2p) emission processes have been detected in the measured angular correlations "heavy-fragment"+p and "heavy-fragment"+p+p, respectively. The ground states of the previously unknown isotopes Cl30 and Cl28 have been observed for the first time, providing the 1p-separation energies Sp of -0.48(2) and -1.60(8), MeV, respectively. The relevant systematics of 1p- and 2p-separation energies have been studied theoretically in the core+p and core+p+p cluster models. The first-time observed excited states of Ar31 allow one to infer the 2p-separation energy S2p of 6(34) keV for its ground state. The first-time observed state in Ar29 with S2p=-5.50(18) MeV can be identified as either a ground state or an excited state according to different systematics

Floral structure and development in the monoecious palm Gaussia attenuata (Arecaceae ; Arecoideae)

Sexual dimorphism, at both the flower and plant level, is widespread in the palm family (Arecaceae), in contrast to the situation in angiosperms as a whole. The tribe Chamaedoreeae is of special interest for studies of the evolution of sexual expression since dioecy appears to have evolved independently twice in this group from a monoecious ancestor. In order to understand the underlying evolutionary pathways, it is important to obtain detailed information on flower structure and development in each of the main clades. Dissection and light and scanning electron microscopy were performed on developing flowers of Gaussia attenuata, a neotropical species belonging to one of the three monoecious genera of the tribe. Like species of the other monoecious genera of the Chamaedoreeae (namely Hyophorbe and Synechanthus), G. attenuata produces a bisexual flower cluster known as an acervulus, consisting of a row of male flowers with a basal female flower. Whereas the sterile androecium of female flowers terminated its development at an early stage of floral ontogeny, the pistillode of male flowers was large in size but with no recognizable ovule, developing for a longer period of time. Conspicuous nectary differentiation in the pistillode suggested a possible role in pollinator attraction. Gaussia attenuata displays a number of floral characters that are likely to be ancestral to the tribe, notably the acervulus flower cluster, which is conserved in the other monoecious genera and also (albeit in a unisexual male form) in the dioecious genera (Wendlandiella and a few species of Chamaedorea). Comparison with earlier data from other genera suggests that large nectariferous pistillodes and early arrest in staminode development might also be regarded as ancestral characters in this tribe

Probing the cluster structure of Li 7 via elastic scattering on protons and deuterons in inverse kinematics

Elastic scattering measurements were performed for the Li7+p system in inverse kinematics at energies of 16, 25, 35, and 38.1 MeV and for the Li7+d system at 38.1 MeV. The heavy ejectiles were detected by the large acceptance MAGNEX spectrometer at the Laboratori Nazionali del Sud in Catania, Italy. The results are analyzed using the Jeukenne-Lejeune-Mahaux and continuum discretized coupled channel frameworks. In the latter case the cluster structure of Li7 proves to be critical for the theoretical interpretation of the experimental results

Elastic scattering measurements for the system 7Be + 28Si at 17.2 MeV

Elastic scattering of 7Be+28Si was studied at several near barrier energies for probing the energy dependence of the optical potential. Our analysis at 17.2 MeV will be presented in this article and discussed, in terms of Continuum Coupled Channel Calculations (CDCC). This research is part of a long term plan concerning the energy dependence of the optical potential for weakly bound projectiles, at near barrier energies and for probing the potential threshold anomaly. The experiment took place at the EXOTIC facility - Laboratori Nationali di Legnaro (LNL), and refers to an angular distribution measurement, using the detector array EXPADES (Exotic Particle Detection System). Results at 9 MeV (Rutherford region) were also analyzed and were used for estimating the solid angle. Our analysis for other energies is under process

Study of the 6Li + p → \rightarrow 3He + 4He reaction in inverse kinematics

Angular distribution measurements were performed for the 6Li + p$\rightarrow$3He + 4He reaction in inverse kinematics at incident energies of 2.7, 3.3, 4.2 and 4.8MeV/u. The detection of both recoils ( 3He and 4He over the laboratory angle range $\theta_{lab}=16^{\circ}$ to $34^{\circ}$ allowed the determination of the angular distribution over a wide angular range in the center-of-mass frame ( $\theta_{c.m.}\sim 40^{\circ}$ to $140^{\circ}$. The results clarify inconsistencies between existing data sets and are consistent with compound nucleus model calculations. © 2015, SIF, Springer-Verlag Berlin Heidelberg

Important influence of single neutron stripping coupling on near-barrier ⁸Li + ⁹⁰Zr quasi-elastic scattering

Quasi-elastic scattering data were obtained for the radioactive nucleus 8Li on a 90Zr target at the near-barrier energy of 18.5MeV over the angular range $\theta_{lab}=15^{\circ}$ to 80\ub0. They were analyzed within the coupled channels and coupled reaction channels frameworks pointing to a strong coupling effect for single neutron stripping, in contrast to 6, 7Li + 90Zr elastic scattering at similar energies, a non-trivial result linked to detailed differences in the structure of these Li isotopes

Probing the cluster structure of 7Li via elastic scattering on protons and deuterons in inverse kinematics

Elastic scattering measurements were performed for the Li7+p system in inverse kinematics at energies of 16, 25, 35, and 38.1 MeV and for the Li7+d system at 38.1 MeV. The heavy ejectiles were detected by the large acceptance MAGNEX spectrometer at the Laboratori Nazionali del Sud in Catania, Italy. The results are analyzed using the Jeukenne-Lejeune-Mahaux and continuum discretized coupled channel frameworks. In the latter case the cluster structure of Li7 proves to be critical for the theoretical interpretation of the experimental results

Total reaction cross sections for Li-8+Zr-90 at near-barrier energies

Total reaction cross sections for the radioactive nucleus Li-8 on Zr-90 are reported at the near-barrier energies of 18.5 and 21.5MeV, derived from quasi-elastic scattering measurements. An analysis of the quasi-elastic scattering results is performed within an optical model framework using the BDM3Y1 interaction and total reaction cross sections are deduced. These quantities, appropriately reduced, are compared with previous data obtained in elastic scattering measurements with well and weakly bound projectiles on various targets and a formula for predicting total reaction cross sections with an uncertainty of similar to 20% is obtained. Further on, the ratios of direct to total reaction cross sections are estimated for 6,8 Li on various targets and are compared with CDCC or CRC calculations. The energy dependence of the optical potential is also discussed

Elastic scattering measurements for the system Be-7+Si-28 at 17.2 MeV

Elastic scattering of Be-7+Si-28 was studied at several near barrier energies for probing the energy dependence of the optical potential. Our analysis at 17.2 MeV will be presented in this article and discussed, in terms of Continuum Coupled Channel Calculations (CDCC). This research is part of a long term plan concerning the energy dependence of the optical potential for weakly bound projectiles, at near barrier energies and for probing the potential threshold anomaly. The experiment took place at the EXOTIC facility - Laboratori Nationali di Legnaro (LNL), and refers to an angular distribution measurement, using the detector array EXPADES (Exotic Particle Detection System). Results at 9 MeV (Rutherford region) were also analyzed and were used for estimating the solid angle. Our analysis for other energies is under process

Important influence of single neutron stripping coupling on near-barrier 8Li + 90Zr quasi-elastic scattering

Quasi-elastic scattering data were obtained for the radioactive nucleus 8Li on a 90Zr target at the near-barrier energy of 18.5MeV over the angular range $\theta_{lab}=15^{\circ}$ to 80°. They were analyzed within the coupled channels and coupled reaction channels frameworks pointing to a strong coupling effect for single neutron stripping, in contrast to 6, 7Li + 90Zr elastic scattering at similar energies, a non-trivial result linked to detailed differences in the structure of these Li isotopes. © 2015, The Author(s)