We provide the first systematic characterization of the structural and photoluminescence properties of optically active centers fabricated upon implantation of 30–100 keV Mg+ ions in synthetic diamond. The structural configurations of Mg-related defects were studied by the electron emission channeling technique for short-lived, radioactive 27Mg implantations at the CERN-ISOLDE facility, performed both at room temperature and 800 °C, which allowed the identification of a major fraction of Mg atoms (∼30 to 42%) in sites which are compatible with the split-vacancy structure of the MgV complex. A smaller fraction of Mg atoms (∼13 to 17%) was found on substitutional sites. The photoluminescence emission was investigated both at the ensemble and individual defect level in the 5–300 K temperature range, offering a detailed picture of the MgV-related emission properties and revealing the occurrence of previously unreported spectral features. The optical excitability of the MgV center was also studied as a function of the optical excitation wavelength to identify the optimal conditions for photostable and intense emission. The results are discussed in the context of the preliminary experimental data and the theoretical models available in the literature, with appealing perspectives for the utilization of the tunable properties of the MgV center for quantum information processing applications.

Summary In a survey of the metazoan ecto‐ and endoparasites of Siganus sutor (Cuvier & Valenciennes, 1835), a commercially important herbivorous fish from the Kenyan coast, sixteen species of parasites are found. The gill parasites include Monogenea (Tetrancistrum sigani Goto & Kikuchi, 1917; Microcotyle mouwoi Ishii & Sawada, 1938; Pseudohaliotrema sp. 1 and sp. 2, and an unidentified Microcotylidae species); Copepoda (Caligus sp. and Hatschekia sp.); and Isopoda (one Gnathiidae species). The intestinal parasites found are Digenea (Opisthogonoporoides cf. hanumanthai Madhavi, 1912; Gyliauchen papillatus Goto & Matsudaira, 1918; Hexangium sigani Goto & Ozaki, 1929; and three other unidentified digeneans); Acanthocephala (Sclerocollum rubrimaris Schmidt & Paperna, 1978); and Nematoda (Procamallanus sigani Yamaguti, 1935). The species listed are first records for the Kenyan coast. Infection prevalence, mean intensity and site specificity are determined for the different parasite species. The parasites have an aggregated frequency distribution in the host population: some individuals of the siganid population are more heavily infected than expected in a random distribution, while others are very little or not at all infected. Résumé On a découvert seize espèces de parasites lors d'une étude des métazoaires ecto‐et endoparasites de Siganus sutor (Cuvier & Valenciennes, 1985), un Poisson herbivore commercialement important de la côte kéyane. Les parasites des branchies comprennent des Monogeneae (Tetrancistrum sigani Goto & Kikuchi, 1917; Microcotyle mouwoi Ishii & Sawada, 1938; Pseudohaliotrema sp.1 & sp.2, et une espèce non identifiée de Microcotylideae); des Copépodes (Caligus sp. et Hatschekia sp.) et un Icopode (une espèce de Gnathiideae). Les parasites intestinaux trouvés appartenaient aux Digeneae (Opisthogonoporoides cf. hanumanthai Madhavi, 1972; Gyliauchen papillatus Goto & Matsudaira, 1918; Hexangium sigani Goto & Ozaki, 1929; et trois autres Digenaeae non identifiés); aux Acanthocephaleae (Sclerocollum rubrimaris Schmidt & Paperna, 1978), et aux Nématodes (Procamallanus sigani Yamaguti 1935). Ces espèces sont rapportées pour la première fois sur la côte kényane. Le degré, l'intensité

The adsorption of molecular deuterium (D 2 ) onto charged cobalt-fullerene-complexes Co n C 60 + (n = 1-8) is measured experimentally in a few-collision reaction cell. The reactivity is strongly size-dependent, hinting at clustering of the transition metal atoms on the fullerenes. Formation and desorption rate constants are obtained from the pressure-dependent deuterogenation curves. DFT calculations indeed find that this transition metal clustering is energetically more favorable than decorating the fullerene. For n = 1, D 2 is predicted to bind molecularly and for n = 2 dissociative and molecular configurations are quasi-isoenergetic. For n = 3-8, dissociation of D 2 is thermodynamically preferred. However, reaching the ground state configuration with dissociated deuterium on the timescale of the experiment may be hindered by dissociation barriers.[a] Dr.

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A new approach to observe the radiative decay of the 229 Th nuclear isomer, and to determine its energy and radiative lifetime, is presented. Situated at a uniquely low excitation energy, this nuclear state might be a key ingredient for the development of a nuclear clock, a nuclear laser and the search for time variations of the fundamental constants. The isomer's γ decay towards the ground state will be studied with a high-resolution VUV spectrometer after its production by the β decay of 229 Ac. The novel production method presents a number of advantages asserting its competitive nature with respect to the commonly used 233 U α-decay recoil source. In this paper, a feasibility analysis of this new concept, and an experimental investigation of its key ingredients, using a pure 229 Ac ion beam produced at the ISOLDE radioactive beam facility, is reported.