[en] The activities presented cover the following topics: heavy ion reactions, gamma ray spectroscopy, applied atomic and nuclear physics, theoretical nuclear physics, data collection and processing, accelerator operation, as well as personnel and publications. (T.A.)

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[en] Thick-target yield of γ-rays emitted in the reactions ¹⁴N(p,p'γ₁)¹⁴N and ¹⁵N(p,αγ₁)¹²C were measured as a function of bombarding energy in order to select the conditions favouring the employment of these reactions in nitrogen isotopic analysis. The applicability of these reactions in the determination of relative as well as absolute nitrogen isotopic abundances was demonstrated at 4.3 MeV bombarding energy. (author)

[en] The radioactive uptake of Medicago sativa and Rye grass in a pasture exposed to the fallout from the Chernobyl reactor accident, was determined in four consecutive harvests covering a period of one year after the accident. In plants of Medicago sativa, inoculated with an effective Rhizobia meliloti strain isolated from Greek soils, a high degree of biological nitrogen fixation was observed at all harvests using N-15 techniques. At the second and third harvests, the percentage nitrogen derived from fixation (%NdfF), the percentage nitrogen derived from soil (%NdfS), as well as the radioactive uptake from the soil remained stable. At the fourth harvest, however, the %NdfF decreased while the %NdfS and the radioactive uptake from soil significantly increased. At the first harvest the radioactivity in both plants, caused mainly by direct fallout contamination, was considerably higher than that observed at the later harvests. Medicago sativa contained significantly less radioactivity than the grass at all harvests, although both plants were grown under the same environmental conditions. Even at the fourth harvest, almost one year after the initial contamination, the radioactivity of grass remained at high levels (20 Bq g^-1 of protein) while in Medicago sativa it assumed considerably lower values (3.6 Bq g^-1 of protein). A possible involvement of biological nitrogen fixation in the reduction of radioactive uptake is discussed. Finally, certain practical conclusions are drawn with respect to a safer management of pastures exposed to radioactivity. (author)

[en] The competition between pn and d evaporation leading to production of the same residual nucleus has been calculated in the framework of the Hauser-Feshbach theory for nine heavy-ion-induced nuclear reactions, each at several bombarding energies, for target-projectile combinations resulting in compound nuclei 12≤A≤40. The observed very good agreement between the experimental and the statistically predicted relative cross sections for pn and d emission indicates that both these exit channels proceed via evaporation from a compound nucleus

[en] The level structure and the decay properties of levels in ⁹⁷Tc up to 2208 keV excitation have been investigated via measurements of excitation functions of singles γ rays and via γγ-coincidence experiments following the ⁹⁷Mo(p,nγ) reaction with proton energies between 1.5 and 8.0 MeV. From these experiments and from high resolution singles energy and directional-correlation measurements an extended scheme has been obtained which includes 69 levels of which about 40 are new. The directional correlations provided unique J/sup [/ assignments for 14 levels, limits for a few others, and multipole mixing ratios for several electromagnetic transitions. The results are compared with unified model calculations

[en] The competition between pn and d evaporation leading to production of the same residual nuclei has been measured for several heavy-ion induced nuclear reactions. γ rays were measured in coincidence with a ΔE-E telescope for 9 reactions, each at several bombarding energies, for target-projectile combinations resulting in compound nuclei 19 < A < 71. An association of the ratio sigma/sub pn/sigma/sub d/ with the maximum excitation energy available to the residual nucleus demonstrates a systematic trend, the significance and potential applications of which are investigated

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[en] The applicability of the ¹⁴(p,p'γ₁)¹⁴N nuclear reaction in the determination of the absolute abundance of ¹⁴N, with a 2% uncertainty, was demonstrated at 4.3 MeV bombarding energy. The fact that almost all of the thick target γ-ray yield resulted from a resonance at Ep=4.0 MeV allowed to consider the necessary stopping-power corrections only at the energy of that resonance. Alternatively, the method was used to obtain the stopping power of 4.0 MeV protons in complex biological materials. (author)