In this study, concentrations of global fallout ⁹⁹Tc in twenty-one surface soil samples collected in Japan were determined by inductively coupled plasma mass spectrometry. The range of ⁹⁹Tc concentrations in rice paddy field, upland field and other soils were determined as 6 - 88, 4 - 8, and 7 - 29 mBq/kg-dry, respectively. The highest average activity ratios of⁹⁹Tc/¹³⁷Cs were found in paddy field soils followed by upland field and other soils. The activity ratios in paddy field samples were one order of magnitude higher than the theoretical one estimated from nuclear fission yield, which was presently calculated as 3.3 × 10^-4. Not only the activity ratio in deposition samples, but also mechanisms of ⁹⁹Tc accumulation in paddy field soils from irrigation of surface water, can explain the high ⁹⁹Tc/¹³⁷Cs activity ratios in soils. The results of vertical distributions of ⁹⁹Tc and ¹³⁷Cs in undisturbed soils showed that the migration rate of ⁹⁹Tc would be slightly faster than that of ¹³⁷Cs, but most of ⁹⁹Tc would still be retained in the 0 - 20 cm layer from the surface.

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The charge distributions of fission products in proton-induced fission of ²³⁸U and ²³²Th were measured in a wide mass range. The most probable charges lay on the proton-rich side in the light fragment region and on the proton-deficient side in the heavy one compared with the unchanged charge distribution hypothesis. This result implies that the charge polarization occurs in the fission process. The charge polarization was examined with respect to the ground-state Q values. The estimations by the Q values fairly well reproduced the experimental most probable charges. These results suggest that the fission path to the most favorable charge division may go through the most energetically favorable path at scission point.

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Binuclear iron (III) spin-crossover complexes, [Fe₂ (salten)₂(az)] (BPh₄)₂ (1) and [Fe₂(salten)₂(cc)](BPh₄)₂ (2) (H₂salten= 2, 2'-[iminobis(3, 1-propanediylnitrilomethylidyne)]bis-phenol, az=4, 4'-azobis-pyridine, and cc=4, 4'-(1, 2-ethenediyl)bis-pyridine), and mononuclear iron (III) spin-crossover complexes, [Fe(pap)₂]ClO₄·H₂O (3) (Hpap = 2-(2-pyridylmethyleneamino)phenol) and [Fe(qsal)₂]NCSe·CH₂Cl₂ (4) (Hqsal = 2-[(8-quinolinylimino)methyl]-phenol), were synthesized and characterized by single-crystal X-ray diffraction, Mössbauer spectra, magnetic susceptibilities, and electronic spectra. The structures of 1 and 2 were determined in the low-spin states at 100 K and the high-spin states at 298 K. The complexes 1 and 2 exhibited the spincrossover behavior; gradual and rapid spin interconversion was observed by means of Mössbauer spectroscopy at 293 K. The structure of 3 in the high-spin state was determined at 293 K. The complex 3 exhibited the abrupt spin transition with thermal hysteresis (T_1/2↑=180 K and T_1/2↓=165 K). The time dependence of the magnetism and the frozen-in effect were observed for the complex 3. Furthermore, light-induced excited spin state trapping effect was observed for the first time for iron (III) complexes. The structure of 4 in the low-spin state was determined at 200 K. The complex 4 exhibited a wide thermal hysteresis loop of 180 K (T_1/2↑ = 392 K and T _1/2↓ = 212 K) in the first cycle, although the hysteresis loop observed for the first cycle is apparent ones. Following the first loop, it shows a two-step spin transition in warming mode (T_1/2 (S1) ↑ = 215 K and T_1/2 (S2) ↑ = 282 K) and a one-step spin transition in cooling mode (T_1/2 ↓ = 212 K).

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By means of correlated measurements of the individual lifetimes of positrons (called positron ages) and of the Doppler shifts of their 2γ-annihilation radiation (Age-Momentum Correlation, acronym AMOC) the room-temperature behaviour of positrons and positronium in n-hexane, tetramethylsilane, benzene, methanol, ethanol, nbutanol, n-hexanol, n-octanol, and water has been investigated. The annihilation parameters of “free” positrons and of para- and orthopositronium (lifetimes and Doppler-broadened lines) have been deduced from a two-dimensional analysis of the AMOC data. The lifetimes of positrons are found to be related to the electronic polarizability of the investigated liquid. The behaviour of the Doppler-broadened free-positron and orthopositronium linewidths is explained in terms of structural and dipolar properties of the liquid molecules.

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A review is given on the recoil studies of photonuclear reactions on complex nuclei at intermediate energies. Recoils of 167 radionuclides formed in the photonuclear reactions of ²⁷Al, ^natV, ^natCu, ⁹³Nb, ^natAg, ^natTa, and ¹⁹⁷Au, induced by bremsstrahlung of end-point energies (E₀) from 600 to 1100 MeV, have been investigated by the thicktarget thick-catcher method. The recoil velocity from the first step and the mean kinetic energy of the residual nuclei in the second step were deduced based on the two-step vector velocity model and discussed by comparing with the reported results on proton-induced reactions. Recoils of ²⁴Na produced from ²⁷Al, ^natV, ^natCu, ^natAg, and ¹⁹⁷Au are of special interest from a viewpoint of a change in the production mechanism with respect to target mass. Reaction yields of 58 and 63 radionuclides produced in the photofission of ¹⁹⁷Au and ²⁰⁹Bi, respectively, were also measured at E₀ = 300-1100 MeV by a catcher foil technique with the aid of intensive chemical separation. The fission characteristics such as the charge and mass distributions and the numbers of pre- and post-fission neutrons were determined. These results were compared with the calculations using the Photon-induced Intranuclear Cascade Analysis 3 code combined with the Generalized Evaporation Model code.

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