No abstract available

[en] Some aspects of clustering phenomena in nuclear structure and reactions are reviewed. Particular emphasis is placed on the relationship between cluster-like states and shape-isomeric states which arise as a result of shell effects in deformed potentials. Some recent evidence in favor of this connection is presented and discussed. 50 refs., 17 figs

[en] This paper explores the relationships between cluster-like configurations and the deformed states which arise as a result of shell structure. The particular case of ²⁴Mg is explored in detail and comparisons with experiment are made. Finally the old problem of the 8⁺ state in ¹⁶O is investigated in the context of shell structure at high angular momentum. (author)

[en] Heavy-ion-α correlation studies following direct heavy-ion reactions can yield information on both the spins of the states excited and the reaction mechanism. Recent experimental correlation data are reviewed and the advantages of the different experimental arrangements compared. It is shown that spin information is continued both in the correlation function itself and in the variation of the correlation function with the primary reaction angle. The extraction of detailed information on the reaction mechanism is discussed. (Auth.)

[en] Simple models are used to explore the relationship between cluster-like configurations and highly deformed states which arise a as a result of shell effects in deformed single particle potentials for light nuclei. It is found that the systematics of the occurrence of clustering phenomena are closely related to the appearance of shell structure in these potentials. Considerable emphasis is place don the use of the pure harmonic oscillator model as a first approximation

[en] The α-decays of states in ¹⁸O have been studied in the sequential breakup reaction ¹²C(¹⁸O, ¹⁸Osup(*) -> ¹⁴C α) at 82 MeV. Double-differential cross sections have been obtained for the states excited in ¹⁸O. A conventional analysis of the decay correlations does not yield unambiguous information on the spins of the states excited. However a systematic dependence of the correlations on the angle of the ¹⁸Osup(*) in the c.m. frame is observed, allowing the determination of the transferred angular momentum. The double-differential cross sections have been analysed with the DWBA and a strong absorption model. The latter allows the extraction of quantitative information on spins and reaction mechanism from the data. (orig.)

[en] Wuosmaa et al. have reported an unusual resonance in the ¹²C(¹²C,¹²C(O₂⁺))¹²C(O₂⁺) reaction at E_cm = 32.5 MeV. More recently resonances have been observed both in other reactions and other ¹²C + ¹²C channels, namely ¹²C(¹²C,¹²C(O₂⁺))¹²C(3^-) and ¹²C(¹²C,¹²C(3^-))¹²C(3^-), at the same centre of mass energy. Here we present a new schematic model of these resonances in which the ¹²C(3^-) states play a central role and illustrate the model by appealing to the classical theory of the symmetric top. We compare a simple partial-wave model with the new data of Wuosmaa et al. for the ¹²C(¹²C, ¹²C(O₂⁺))¹²C(O₂⁺) reaction at E_cm = 32.5 MeV to support the new model. Although we still require several incident partial waves to be contributing simultaneously, we do not require a very large moment of inertia in contrast to our previous shape eigenstate interpretation. We believe that our new model provides a better consistent explanation of all the data mentioned above. (author). 24 refs., 3 figs

[en] The ¹²C - ¹²C resonances have been investigated via the reactions ¹²C(¹²C, αα)¹⁶O and ¹²C(¹²C, α⁸Be)¹²C using beams from the Oxford Folded Tandem. The two lighter reaction products were detected in coincidence at angular separations around 180 deg C in the centre of mass using position sensitive detectors. Kinematic reconstruction of the three body final state yielded α - α and α - ⁸Be angular correlations which were sensitive to the spins of the resonances decaying to the ground states of ¹⁶O and ¹²C respectively. Many of the spin measurements confirm earlier assignments based on studies of other decay channels. Some new 16⁺ assigments are made. The results are discussed in the context of a recent theoretical interpretation based on the Bloch-Brink α-cluster model. (author)

[en] Recently a six-alpha chain state has been discovered in ²⁴Mg. The Bloch-Brink cranked cluster model shows that linear chains of alpha particles are associated with stable minima in the potential-energy surface for all 4N-nuclei. Experimental candidates in ⁸Be, ¹²C and ¹⁶O have already been identified. Using a Brink-Boeker effective interaction, and allowing free variation of all parameters, we calculate the geometric arrangements and energies of the lowest alpha-chain states. These configurations are then cranked to predict the maximum angular momenta and the excitation energies that they can sustain. We conclude the states similar to that in ²⁴Mg should also be accessible to experimental investigation in other nuclei. (orig.)

[en] We examine the properties of the in-plane correlation between the initial scattering angle and the angle at which subsequent particle decay occurs, following a forward angle heavy ion reaction. The results are obtained in the strong absorption limit. In particular, we explain the recent experimental observation that there is a systematic spin-dependence of the correlation distributions on the initial scattering angle of the excited nucleus. We generalize this result to the case of nuclei with non-zero spins in the decay channel, and we also obtain closed form expressions for the correlation function under general matching conditions. (orig.)