Cut-rose production in response to planting density in two contrasting cultivars

Growing in lower planting density, rose plants produce more assimilates, which can be used to produce more and/or heavier flowering shoots. The effect of planting density was investigated during a period including the first five flowering flushes of a young crop. In a heated greenhouse two cut-rose cultivars were grown under bent canopy management. ‘Akito’ on own-roots and ‘Ilios’ on ‘Natal Briar’ rootstock were planted with densities of 8 and 4 plants per m2. Starting at the end of June 2007, flowering shoots were harvested over a time span of eight months. Based on ‘flowering flushes’, times of high harvest rate, the harvesting time span could be divided into five consecutive periods, each including one flush. The cultivars showed contrasting responses to planting density. In the first three periods the response in ‘Ilios’ was extraordinary, because at low density plants did not produce more flowering shoots, as would be expected. However, the response in shoot fresh weight was larger for ‘Ilios’ than for ‘Akito’, 35% compared to 21% over the entire study period. The results imply that there was a genetic difference in the effect of assimilate availability and/or local light environment. During the first three periods, these factors can not have influenced shoot number in ‘Ilios’, while they did in ‘Akito’. It is suggested that decreases of assimilate availability in winter caused the shoot number response to emerge for ‘Ilios’ later on

Tetrahedral Symmetry in Ground- and Low-Lying States of Exotic A ~ 110 Nuclei

Recent theoretical calculations predict a possible existence of nuclei with tetrahedral symmetry: more precisely, the mean-field hamiltonians of such nuclei are symmetric with respect to double point-group Td. In this paper, we focus on the neutron-rich Zirconium isotopes as an example and present realistic mean-field calculations which predict tetrahedral ground-state configurations in 108,110Zr and low-lying excited states of tetrahedral symmetry in a number of N > 66 isotopes. The motivations for focusing on these nuclei, as well as a discussion of the possible experimental signatures of tetrahedral symmetry are also presented.Comment: Accepted in Phys. Rev. C - Rapid Communication

Spectroscopy of 35^{35}P using the one-proton knockout reaction

The structure of $^{35}$P was studied with a one-proton knockout reaction at88~MeV/u from a $^{36}$S projectile beam at NSCL. The $\gamma$ rays from thedepopulation of excited states in $^{35}$P were detected with GRETINA, whilethe $^{35}$P nuclei were identified event-by-event in the focal plane of theS800 spectrograph. The level scheme of $^{35}$P was deduced up to 7.5 MeV using$\gamma-\gamma$ coincidences. The observed levels were attributed to protonremovals from the $sd$-shell and also from the deeply-bound $p\_{1/2}$ orbital.The orbital angular momentum of each state was derived from the comparisonbetween experimental and calculated shapes of individual ($\gamma$-gated)parallel momentum distributions. Despite the use of different reactions andtheir associate models, spectroscopic factors, $C^2S$, derived from the$^{36}$S $(-1p)$ knockout reaction agree with those obtained earlier from$^{36}$S($d$,\nuc{3}{He}) transfer, if a reduction factor $R\_s$, as deducedfrom inclusive one-nucleon removal cross sections, is applied to the knockout transitions.In addition to the expected proton-hole configurations, other states were observedwith individual cross sections of the order of 0.5~mb. Based on their shiftedparallel momentum distributions, their decay modes to negative parity states,their high excitation energy (around 4.7~MeV) and the fact that they were notobserved in the ($d$,\nuc{3}{He}) reaction, we propose that they may resultfrom a two-step mechanism or a nucleon-exchange reaction with subsequent neutronevaporation. Regardless of the mechanism, that could not yet be clarified, thesestates likely correspond to neutron core excitations in \nuc{35}{P}. Thisnewly-identified pathway, although weak, offers the possibility to selectivelypopulate certain intruder configurations that are otherwise hard to produceand identify.Comment: 5 figures, 1 table, accepted for publication in Physical Review

Shell Model Study of the Neutron-Rich Nuclei around N=28

We describe the properties of the neutron rich nuclei around N=28 in the shell mode framework. The valence space comprises the $sd$ shell for protons an the $pf$ shell for neutrons without any restriction. Good agreement is found with the available experimental data. The N=28 shell closure, even if eroded due to the large neutron excess, persists. The calculations predict that $^{40}$S and $^{42}$S are deformed with $\beta=0.29$ and $\beta=0.32$ respectively.Comment: 17 pages and 19 figures, LateX, RevTe

How magic is the magic 68Ni nucleus?

We calculate the B(E2) strength in 68Ni and other nickel isotopes using several theoretical approaches. We find that in 68Ni the gamma transition to the first 2+ state exhausts only a fraction of the total B(E2) strength, which is mainly collected in excited states around 5 MeV. This effect is sensitive to the energy splitting between the fp shell and the g_{9/2}orbital. We argue that the small experimental B(E2) value is not strong evidence for the double-magic character of 68Ni.Comment: 4 pages, 4 figure

Spectroscopy of 28^{28}Na: shell evolution toward the drip line

Excited states in $^{28}$Na have been studied using the $\beta$-decay of implanted $^{28}$Ne ions at GANIL/LISE as well as the in-beam $\gamma$-ray spectroscopy at the NSCL/S800 facility. New states of positive (J$^{\pi}$=3,4$^+$) and negative (J$^{\pi}$=1-5$^-$) parity are proposed. The former arise from the coupling between 0d$\_{5/2}$ protons and a 0d$\_{3/2}$ neutron, while the latter are due to couplings with 1p$\_{3/2}$ or 0f$\_{7/2}$ neutrons. While the relative energies between the J$^{\pi}$=1-4$^+$ states are well reproduced with the USDA interaction in the N=17 isotones, a progressive shift in the ground state binding energy (by about 500 keV) is observed between $^{26}$F and $^{30}$Al. This points to a possible change in the proton-neutron 0d$\_{5/2}$-0d$\_{3/2}$ effective interaction when moving from stability to the drip line. The presence of J$^{\pi}$=1-4$^-$ negative parity states around 1.5 MeV as well as of a candidate for a J$^{\pi}$=5$^-$ state around 2.5 MeV give further support to the collapse of the N=20 gap and to the inversion between the 0f$\_{7/2}$ and 1p$\_{3/2}$ levels below Z=12. These features are discussed in the framework of Shell Model and EDF calculations, leading to predicted negative parity states in the low energy spectra of the $^{26}$F and $^{25}$O nuclei.Comment: Exp\'erience GANIL/LISE et NSCL/S80

New pathway to bypass the 15O waiting point

We propose the sequential reaction process $^{15}$O($p$,$\gamma)(\beta^{+}$)$^{16}$O as a new pathway to bypass of the $^{15}$O waiting point. This exotic reaction is found to have a surprisingly high cross section, approximately 10$^{10}$ times higher than the $^{15}$O($p$,$\beta^{+}$)$^{16}$O. These cross sections were calculated after precise measurements of energies and widths of the proton-unbound $^{16}$F low lying states, obtained using the H($^{15}$O,p)$^{15}$O reaction. The large $(p,\gamma)(\beta^{+})$ cross section can be understood to arise from the more efficient feeding of the low energy wing of the ground state resonance by the gamma decay. The implications of the new reaction in novae explosions and X-ray bursts are discussed.Comment: submitte

Probing Nuclear forces beyond the drip-line using the mirror nuclei 16^{16}N and 16^{16}F

Radioactive beams of $^{14}$O and $^{15}$O were used to populate the resonant states 1/2$^+$, 5/2$^+$ and $0^-,1^-,2^-$ in the unbound $^{15}$F and $^{16}$F nuclei respectively by means of proton elastic scattering reactions in inverse kinematics. Based on their large proton spectroscopic factor values, the resonant states in $^{16}$F can be viewed as a core of $^{14}$O plus a proton in the 2s$_{1/2}$ or 1d$_{5/2}$ shell and a neutron in 1p$_{1/2}$. Experimental energies were used to derive the strength of the 2s$_{1/2}$-1p$_{1/2}$ and 1d$_{5/2}$-1p$_{1/2}$ proton-neutron interactions. It is found that the former changes by 40% compared with the mirror nucleus $^{16}$N, and the second by 10%. This apparent symmetry breaking of the nuclear force between mirror nuclei finds explanation in the role of the large coupling to the continuum for the states built on an $\ell=0$ proton configuration.Comment: 6 pages, 3 figures, 2 tables, accepted for publication as a regular article in Physical Review