Competing T = 0 and T = 1 structures in the N = Z nucleus 3162Ga

The low-lying levels in the odd-odd N = Z nucleus 62Ga have been identified for the first time. These data reveal a cascade of stretched-E2 transitions based on a T = 0, 1+ bandhead which decays directly to the T = 1, 0+ ground state. The observed levels are interpreted in the context of theshell model, using as a basis, the pf5/2g9/2 orbits with a 56Ni core

High-spin study of rotational structures in 72Br

High-spin states in 3572Br37 were studied using the 40Ca(36Ar, 3pn) reaction. The existing level scheme has been significantly modified and extended. Evidence has been found for a spin reassignment of -1ℏh to the previously observed negative-parity band, which carries implications for the interpretation of a signature inversion in this structure. One signature of the previously assigned positive-parity band is interpreted as negative parity and has been extended to I π=(22-) and its signature partner has been observed up to Iπ = (19-) for the first time. The remaining positive-parity band has been extended to Iπ=(29+). A sequence of states observed to Iπ=(22+) may be the signature partner of this structure. Configurations have been assigned to each of these three structures through comparisons to cranked Nilsson-Strutinsky calculations

Symmetries in the nuclei near the centre of the f7_2 shell

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN023426 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Action of a diffusible target-derived chemoattractant on cortical axon branch induction and directed growth

Cortical axons innervate their brainstem target, the basilar pons, by the initiation and extension of collateral branches interstitially along their length. To address whether a diffusible pons-derived chemoattractant controls these events, we used cocultures in collagen matrices and time-lapse microscopy. Pontine explants enhanced by 5-fold the de novo initiation of transient branches along cortical axons; most branches were directed toward pons. Of the branches extended toward pons, 2%-3% were stabilized; those extended away were not. Pontine explants also enhanced the stable bifurcation of growth cones and prompted directional changes by growth cone turning and collateral extension. These effects were distance dependent and mimicked by pons-conditioned medium. This evidence indicates that the pons activity promotes branch initiation interstitially along cortical axons, a novel property for a chemoattractant, and provides a directional cue for their growth. These findings suggest that the pons chemoattractant serves as a diffusible target-recognition molecule.Peer Reviewe

High-spin study of rotational structures in Br-72

High-spin states in Br-72(35)37 were studied using the Ca-40(Ar-36,3pn) reaction. The existing level scheme has been significantly modified and extended. Evidence has been found for a spin reassignment of -1h to the previously observed negative-parity band, which carries implications for the interpretation of a signature inversion in this structure. One signature of the previously assigned positive-parity band is interpreted as negative parity and has been extended to I-pi=(22(-)) and its signature partner has been observed up to I-pi=(19(-)) for the first time. The remaining positive-parity band has been extended to I-pi=(29(+)). A sequence of states observed to I-pi=(22(+)) may be the signature partner of this structure. Configurations have been assigned to each of these three structures through comparisons to cranked Nilsson-Strutinsky calculations

Nonyrast high-spin states in N=Z 44Ti

High-spin states have been investigated in the N-Z=22 nucleus 44Ti. A newly observed set of states with J?=6+ , 8 + , 10+ , and 12+ are assigned to be members of a band built upon an excited 0+ state. This band displays rotational-like level spacings, with a near-linear J(J+1) dependence. A third set of J?=8+ , 10+ , and 12+ states have also been tentatively assigned and a negative-parity intruder band has been extended to J? =13-. Comparisons with df-shell model calculations show a good agreement for both energy levels and branching ratios. These calculations indicate that the excited 0+ band is dominated by a mixture of 8p-4h and 6p-2h configurations relative to 40Ca

Neutron-proton pairing, Coulomb effects and shape coexistence in odd-odd N= Z 46V

High-spin states up to the f7/2-shell band termination at J? = 15+ have been observed in the odd-odd N = Z = 23 nucleus V. A revised and significantly extended level scheme contains two distinct structures corresponding to spherical and prolate shapes. A band exhibiting rotational-like behaviour in the latter structure has excellent correspondence with the yrast sequence in Ti and is therefore assumed to be a T = 1 configuration. The difference between excited analogue states in the two nuclei is interpreted as a Coulomb effect and its variation with spin associated with np-pair alignment effects in V. Shell-model calculations have been performed and are in good quantitative agreement with experimental level energies. The competition between T = 1 and T = 0 structures is also reproduced. © 1999 Elsevier Science B.V. All rights reserved.Scientific Committee on Antarctic Research Engineering and Physical Sciences Research Council Komitet Badan Naukowych Natural Sciences and Engineering Research Council of Canada Engineering and Physical Sciences Research CouncilThe authors thank both Alfredo Poves and Alex Brown for permission to use results from their shell model codes and for helpful discussions. We also thank those responsible for all aspects of the PEX collaboration. This work was supported by the United Kingdom Engineering and Physical Sciences Research Council (EPSRC) from whom D. E. Appelbe was in receipt of an EPSRC studentship. A. Maj is grateful to the Polish State Committee for Scientific Research for partial financial support (KBN Grant No. 2 P03B 001 16). This work was also supported by the Danish Natural Science Research Council

Gamma-ray spectroscopy of high spin states near N = Z in the f7/2 shell

EG and G ORTEC;Polish State Committee for Scientific ResearchProceedings of the 1998 33rd Zakapone School of Physics, International Conference on Nuclear Physics -- 1 September 1998 through 9 September 1998 -- Zakopane -- 55236Two pairs of mirror-nuclei, 2549Mn/2449Cr and 2447Cr/2347V, and the odd-odd N = Z nucleus 2346V have been studied up to the f7/2-shell band termination states. Differences in energy between isobaric analogue states in these nuclei have been measured and interpreted in terms of Coulomb effects. Through this work, we have shown that Coulomb energies are extremely sensitive to nuclear effects such as particle alignments, band terminations and shape changes. This has allowed us to investigate the extent to which the Coulomb energy can be used as a probe of the nuclear structure

Field-cycling long-lived-state NMR of 15N2 spin pairs

A range of nuclear magnetic resonance spectroscopy and imaging applications are limited by the short lifetimes of magnetisation in solution. Long-lived states, which are slowly relaxing configurations of nuclear spins, have been shown to alleviate this limitation. Long-lived states have decay lifetimes significantly exceeding the longitudinal relaxation time , in some cases by an order of magnitude. Here we present an experimental case of a long-lived state for a 15N labelled molecular system in solution. We observe a strongly biexponential decay for the long-lived state, with the lifetime of the slowly relaxing component exceeding 40 minutes, ∼21 times longer than the spin-lattice relaxation time . The lifetime of the long-lived state was revealed by using a dedicated two-field NMR spectrometer capable of fast sample shuttling between high and low magnetic fields, and the application of a resonant radiofrequency field at low magnetic field. The relaxation characteristics of the long-lived state are examined