Irradiated gases, transition yields

The sources most commonly used so far consisted of sintered disks containing about 100 mg ZnO enriched with 90% Zn. The disks were irradiated with 12 MeV deuterons or 30 MeV He particles, to yield the 78 h activity of Ga, and then annealed by heating in oxygen to 700-1,000 K for about 12 h and cooling down slowly (about 50 K h ) to room temperature. A Nal scintillation counter, 2-3 mm thick, is suitable for the detection of the 93 keV y-rays. Because of the relatively high transition energy, both source and absorber are generally kept at liquid helium temperature. 

Photochemical, thermal, and transition metal catalyzed decomposition of diazoacetonitrile in the presence of an alkene yields cyclopropanecarbonitriles by transfer of cyanocarbene (see Houben-Weyl, Vol. E19b, pl202). If the UV irradiation was carried out in (Z)-but-2-ene as solvent, cw-2,3-dimethylcyclopropane-l-carbonitrile (c -l) was formed as the major product cisjtrans 94 6). The percentage of the franj-product can be decreased by the addition of a radical scavenger, such as 1,2-diphenylethene, whereas it can be increased by dilution with dichloromethane. By carrying out the decomposition of diazoacetonitrile as a gas-phase thermolysis, fm i -2,3-dimethylcyclopropane-l-carbonitrile (irans-l) becomes the major product of the cyclopropanation cisltrans 38 62). ... 

The high ion yield of benzene and other aromatic molecules found in low pressure gas phase studies suggests the use of these ions in preparative phtochemistry in solution. The absorption spectrum of benzene iy wat r as a solvent shows a weak band around 250 nm (E = 200 1 mole cm ) corresponding to the S S transition (see sec fon II). The photochemistry fo this molecule exhibits a great manifold of processes. Pure benzene can be transformed by irradiation in this spectral region into various ring isomers, open chain valence isomers and other minor products. In aqueous solution benzene may be photochemically oxidized to formyl-cyclopentadiene-1,3. This oxidation is believed to proceed via the formation of benzvalene in the first step which is rapidly oxidized - with and without oxygen, eqn. (1) - to the aldehyde... 

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