[en] ⁷³Se labelled 2-selenouracil was prepared by the isotope exchange reaction method. It has been well known that in order to prepare labelled compounds in high specific activity by exchange reaction, the substrate compounds have to be used in small quantities. For 2-selenouracil, however, the reaction in low concentration is not always preferable for the labelling of high specific activity within a limited time. The optimum conditions for the preparation of [2-⁷³Se]-2-selenouracil of maximum specific activity were determined. (author)

[en] Recoil sulfur atoms from the nuclear transformation of ³⁵Cl(n,p) ³⁵S were allowed to react with gaseous ethane in the presence or absence of various additives. Hydrogen sulfide was one of the main products, with the yield remarkably affected by the addition of nitrogen monoxide. The yield was increased at low concentration levels of nitrogen monoxide, but decreased at high concentration levels. The primary yield of hydrogen sulfide was estimated to be ca 7.8% of which ca. 3.6% was scavengeable by oxygen. The scavengeable yield is considered to be a product of the reaction of thermalized sulfur atoms. The photochemically produced sulfur atoms are known to yield no hydrogen sulfide in reaction with ethane. The discrepancy between the recoil reaction and the photochemical reaction was investigated using various additives. (orig.)

No abstract available

[en] The sulfur atoms produced by the nuclear transformation of ³⁵Cl(n,p)³⁵S were allowed to react with gaseous ethane in the presence or in the absence of radical scavengers. The products were hydrogen sulfide, methanethiol, ethanethiol, dimethyl sulfide, and other sulfur-containing compounds. The yield of the C-H insertion product (ethanethiol) increased upon the addition of a small amount of the scavenger and then decreased with an increase in the amount of the scavenger to give a constant value, but the yield of the C-C insertion product (dimethyl sulfide) did not vary. The increase in the ethanethiol yield at low concentrations of the scavenger may be ascribed to a protective effect by the scavenger. By the addition of ethanethiol before thermal-neutron irradiation, the yield of ethanethiol was increased, but that of dimethyl sulfide was not increased, therefore the primary yield of ethanethiol could be determined. The spin state of the reactive sulfur atoms in the thermal-insertion reaction was also estimated to be the ³P state upon the addition of COS and C₂H₄. (author)

[en] With a view to separating isotopic bromine by the use of the laser, the absorption spectrum of bromine molecules, ¹Σ(0⁺g) (ground level) → ³PI(0⁺u) (predissociation level), was measured by the tunable dye laser and isotope shifts were observed. The molecules selectively excited by the irradiation of the dye laser were predissociated and reacted with hydrogen iodide (HI) to give hydrogen bromide (HBr). The obtained over-all maximum separation factor was 1.02. If the quantity of HBr produced by the dark reaction was subtracted from that of total HBr product, the maximum separation factor is 1.15. This is almost in agreement with the separation factor 1.2 estimated from the limited line width of the laser. (auth.)

No abstract available