Abstract. Elastic scattering of α-particle and some tightly-bound light nuclei has shown the pattern of rainbow scattering at medium energies, which is due to the refraction of the incident wave by a strongly attractive nucleus-nucleus potential. This review gives an introduction to the physics of the nuclear rainbow based essentially on the optical model description of the elastic scattering. Since the realistic nucleusnucleus optical potential (OP) is the key to explore this interesting process, an overview of the main methods used to determine the nucleus-nucleus OP is presented. Given the fact that the absorption in a rainbow system is much weaker than that usually observed in elastic heavy-ion scattering, the observed rainbow patterns were shown to be linked directly to the density overlap of the two nuclei penetrating each other in the elastic channel, with a total density reaching up to twice the nuclear matter saturation density ρ 0 . For the calculation of the nucleus-nucleus OP in the doublefolding model, a realistic density dependence has been introduced into the effective M3Y interaction which is based originally on the G-matrix elements of the Reid-and Paris nucleon-nucleon (NN) potentials. Most of the elastic rainbow scattering data were found to be best described by a deep real OP like the folded potential given by this density dependent M3Y interaction. Within the Hartree-Fock formalism, the same NN interaction gives consistently a soft equation of state of cold nuclear matter which has an incompressibility constant K ≈ 230 − 260 MeV. Our folding analysis of numerous rainbow systems has shown that the elastic α-nucleus and nucleus-nucleus refractive rainbow scattering is indeed a very helpful experiment for the determination of the realistic K value. The refractive rainbow-like structures observed in other quasielastic scattering reactions have also been discussed. Some evidences for the refractive effect in the elastic scattering of unstable nuclei are presented and perspectives for the future studies are discussed.

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The physical interpretation of nuclear rainbow scattering within the frame of the optical model is critically investigated. Starting from the properties of the Luneburg lens, a gradient index device that displays refractive features similar to those of the nuclear potential, important differences between the mechanisms producing the nuclear and optical rainbows are pointed out.

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Increasing levels of CO2 in the atmosphere are expected to cause climatic change with negative effects on the earth's ecosystems and human society. Consequently, a variety of CO 2 disposal options are discussed, including injection into the deep ocean. Because the dissolution of CO2 in seawater will decrease ambient pH considerably, negative consequences for deep-water ecosystems have been predicted. Hence, ecosystems associated with natural CO2 reservoirs in the deep sea, and the dynamics of gaseous, liquid, and solid CO 2 in such environments, are of great interest to science and society. We report here a biogeochemical and microbiological characterization of a microbial community inhabiting deep-sea sediments overlying a natural CO 2 lake at the Yonaguni Knoll IV hydrothermal field, southern Okinawa Trough. We found high abundances (>10 9 cm ؊3 ) of microbial cells in sediment pavements above the CO2 lake, decreasing to strikingly low cell numbers (10 7 cm ؊3 ) at the liquid CO2͞CO2-hydrate interface. The key groups in these sediments were as follows: (i) the anaerobic methanotrophic archaea ANME-2c and the Eel-2 group of Deltaproteobacteria and (ii) sulfur-metabolizing chemolithotrophs within the Gamma-and Epsilonproteobacteria. The detection of functional genes related to one-carbon assimilation and the presence of highly 13 C-depleted archaeal and bacterial lipid biomarkers suggest that microorganisms assimilating CO2 and͞or CH4 dominate the liquid CO2 and CO 2-hydrate-bearing sediments. Clearly, the Yonaguni Knoll is an exceptional natural laboratory for the study of consequences of CO 2 disposal as well as of natural CO2 reservoirs as potential microbial habitats on early Earth and other celestial bodies.anaerobic oxidation of methane ͉ chemolithotroph ͉ CO2 disposal ͉ CO 2 hydrate ͉ liquid CO2

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We investigate the linear chain configurations of four-α clusters in 16O using a Skyrme cranked Hartree-Fock method and discuss the relationship between the stability of such states and angular momentum. We show the existence of a region of angular momentum (13-18ℏ) where the linear chain configuration is stabilized. For the first time we demonstrate that stable exotic states with a large moment of inertia (ℏ2/2Θ∼0.06-0.08  MeV) can exist.

The n-particle clustering structure of "Mo and ' Po, which is of interest for investigating the persistence of n clustering in heavy nuclei, is studied within the framework of a local potential approach using a double folding model. It is shown that the model, which describes n scattering from Zr well, locates the ground state of Mo at the energy corresponding to experiment. A similar result was obtained for the n + 'Pb system. It is found that the model gives not only the ground band of Mo and ' Po as compact o.-cluster states but also predicts other developed genuine n-cluster states below and near the Coulomb barrier.PACS numbers: 21.60. Gx, 25.55.Ci, 27.60.+j, 27.80. + w Alpha clustering is very important in light nuclei [1]. As the nucleus becomes heavier, the spin-orbit force becomes stronger; therefore it has been considered that n-cluster correlation may be suppressed in heavy nuclei. However, recent observations of a theoretically predicted K = 0 band of a parity doublet both in Ti [2 -4] and Ca [5,6] have given firm evidence that the n-cluster model persists in the beginning of the fp-shell region. This encourages us to study further the o. -clustering aspects in much heavier nuclei.Mo and ' Po are typical nuclei which have two protons and two neutrons outside the double closed shell; however, their n-clustering aspects are scarcely understood.