[en] There has been an enormous amount of investigation of the luminescence of the uranyl (UO₂²⁺) ion and its photochemical reactions. Considerable attention has been given to a study of the photochemical reduction of UO₂²⁺ by organic compounds. It was long considered that UV irradiation of aqueous solutions of uranyl not containing organic impurities did not lead to any significant change in the chemical composition of the solution. However, the high oxidation-reduction potential of UO₂²⁺ (2.7 V) permits its reaction with water. Burrows and Kemp have proposed that some portion of UO₂⁺ and the ·OH radicals, which do not enter a geminal reaction, leave the cage and small amounts of U(IV) and H₂O₂ then accumulate in the solution. And the mechanism for the photochemical reduction of uranyl by water through electron transfer has found only indirect evidence by τ-metry (relative to the quenching of the photoluminescence of UO₂²⁺ by a water molecule). For a study of the radiation chemical reduction of uranium(IV) in aqueous sulfuric acid in the absence of ·OH radical acceptors, the authors proposed a chemiluminescence (CL) method based on the possibility of detecting small amounts of uranium(IV) (down to 10^-9 mole/liter) on the background of a significant excess of uranium(VI)(up to 10^-1 mole/liter) using the chemiluminescence of the oxidation of tetravalent uranium compounds by xenon trioxide

[en] The infrared absorption spectrum in the 16-17 μm region of the transient UF₅ molecule formed form laser photolysis of UF₆ is presented. The absorption contour and the intensity measurements allow tentative assignment of the molecular structure. (Auth.)

[en] Two pheomelanin model compounds were prepared and their photochemistries examined. Upon irradiation, an oxygen-mediated photopolymerization reaction was observed. The photopolymers obtained were characterized by their apparent molecular weights, UV and fluorescence spectra. The implications of these findings with respect to the structure and photobiology of pheomelanin are discussed. (author)

[en] Fluoroquinolones like difloxacin (DIF) and sarafloxacin (SARA) are adsorbed in soil and enter the aquatic environment wherein they are subjected to photolytic degradation. To evaluate the fate of DIF and SARA, their photolysis was performed in water under stimulated natural sunlight conditions. DIF primarily degrades to SARA. On prolonged photodegradation, seven photoproducts were elucidated by HR-LC-MS/MS, three of which were entirely novel. The residual anti-bacterial activities of DIF, SARA and their photoproducts were studied against a group of pathogenic strains. DIF and SARA revealed potency against both Gram-positive and -negative bacteria. The photoproducts also exhibited varying degrees of efficacies against the tested bacteria. Even without isolating the individual photoproducts, their impact on the aquatic environment could be assessed. Therefore, the present results call for prudence in estimating the fate of these compounds in water and in avoiding emergence of resistance in bacteria caused by the photoproducts of DIF and SARA. - Assessment of the residual anti-bacterial efficacies of difloxacin, sarafloxacin and their photoproducts in water, and estimating their impact on the aquatic environment in inducing resistance to microorganisms.

[en] A multistage process for isotopic enrichment is provided. A gaseous mixture of the primary isotope substrate and a primary transfer agent is irradiated with a laser at a first wavelength. After the primary transfer agent has been removed, a secondary transfer agent is added and the mixture is irradiated at a second wavelength. The enriched product is then separated from the secondary transfer agent and the depleted substrate. The overall separation factor is the product of the individual separation factors of each stage

No abstract available

[en] A general description of a decay process as a half-collision is presented. Two different sets of definitions of the non-decay probabilities and the spectra of the decay products are compared. A special role is stressed of a bound state of the total Hamiltonian, which may be generated in the threshold region. An example of near-threshold photodetachment is pointed out as the case in which distinguishing between different definitions may be essential. (orig.)

[en] The radiation chemistry of oxygen discharges is better-studied system. The discharges were made by irradiation with high energy helium and lithium ions created by a neutron-induced reaction in boron (10). A detailed numerical model and a simplified analytical model of oxygen radiolysis have been developed to interpret the data. A summary of the data on the ozone yield from irradiation of He-O2, Ne-O2 and Ar-O2 is presented. Dose rates are also indicated. The present work appears to be the first to measure the steady state ozone concentration in noble gas-oxygen discharges and the effect of SF6 on this steady state concentration. 106 refs

[en] The authors have measured the differential cross section for two-body deuteron photodisintegration at θ_cm = 90 degrees, 114 degrees and 143 degrees, and for photon energies between 0.8 and 1.8 GeV. At energies above ≅1.2 GeV, the data at θ_cm = 90 degrees, and 114 degrees appear to obey a simple scaling law predicted by constituent-counting rules assuming parton degrees of freedom for the deuteron and nucleons. The shape of the angular distribution shows an abrupt change at E_γ ≥ 1.4 GeV, in that at 1.4 and 1.6 GeV cross sections peak at θ_cm = 143 degrees, but this is not the case for E_γ < 1.2 GeV. Agreement with model calculations based on meson exchange and on open-quotes reduced nuclear amplitudesclose quotes is discussed

[en] The hunt for complex organic molecules (COMs) is a major concern for understanding the possible role of interstellar chemistry in the synthesis of the molecules that ultimately may be at the origin of life. A comprehensive screening of the 14 species effectively observed under 32 different isomeric forms in the interstellar medium has been done by means of high-level quantum chemical simulations. Confrontation between calculations and observations shows that when several isomers of the same generic formula are identified, it is always the most stable one that is the most abundant. Moreover, the abundance ratio of the most stable isomer to the other isomers is directly related to their energy difference. What can be seen as a minimum energy principle is verified in molecular clouds, hot cores/corinos, photodissociation regions, and asymptotic giant branch stars. The few exceptions encountered could be rationalized either by the existence of different routes of formation with no intermediate in common and/or specific depletion on the grains of one isomer with respect to the others.