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Relative contributions of direct molecular elimination and radical disproportionation reactions to formation of nonrandomized nitrogen in photolysis of hydrazine
Photochemical transformation probe technique using collisional sensitization of fluorescence by positive trivalent Eu and Tb ions
Photoreduction of p, p prime-dimethoxybenzophenone /DMB/ in isopropyl alcohol for near UV irradiation, using trivalent Tb ion fluorescence to determine conversion
Primary processes leading to atomic and molecular hydrogen formation in hydrogen peroxide photolysis at 1236 A, noting OH formation
Photochemical reactions for mesospheric oxygen, oxygen-hydrogen, and oxygen-hydrogen-nitrogen atmospheres calculated for atomic oxygen/ozone ratios
Resonance fluorescence techniques for determining upper atmosphere hydroxyl radical
Radiation induced photochemical reactions in polyisoprene and polybutadiene thin films including microstructural changes
Vacuum ultraviolet photoionization and photodissociation of associated and polymeric systems of liquid water and alcohols
A quantitative discussion is presented of the lifetime against photodecomposition, or the probability of photodecomposition, of interstellar molecules. In addition to photodissociation, molecules can also be destroyed by interaction with high energy radiation and energetic particles. These processes are much less effective than destruction by ultraviolet radiation. However, when the ultraviolet is highly attenuated in clouds, the energetic radiation and particles will persist and will become relatively more important and the ultimate lifetimes in clouds may depend upon these processes.
The mechanisms of the direct photochemical reactions which occur in unsaturated polymers when irradiated as thin films in vacuo are reviewed. Important reactions in 1,4-polyisoprene and 1,4-polybutadiene are cis-trans isomerization, loss of 1,4-unsaturation, formation of new external double bonds (vinylidene and/or vinyl units) and cyclopropyl formation. In 1,2-polybutadiene and 3,4-polyisoprene, on the other hand, the main reaction is consumption of the external double bonds through cyclization. Recent work on the photoinduced microstructural changes in cis and trans polypentenamers is also discussed.
Requirements for determining the source of C3 in comets are discussed, and include high resolution observation of the region near the nucleus, and near-continuous coverage.
The formation processes for C3 or C2 in comets are discussed along with the possibility of trapping the radical inside the clathrates.
Publications are listed covering NASA research from 1966 to 1973. Several major works covering chloroplast reactions, aerobic green algae and hydrogenease, production of molecular hydrogen, and hydrogen and nitrogen metabolism in purple bacteria are summarized.
Gas phase processes involving interstellar molecules are considered. The primary process is photodissociation in the ambient radiation field. In obscured regions, a combination of Johnson's (1965) and Stecher's (1969) Perseus extinction curves was used to obtain the radiation field as a function of the extinction at 5,500 A. On the basis of laboratory measurements, it is concluded that the molecules of water, ammonia, methane, and formaldehyde have lifetimes less than one hundred years.
The atmospheric composition of Mars is presented, and the applicability of laboratory data on CO2 absorption cross sections and quantum yields of dissociation is discussed. A summary and critical evaluation are presented on the various mechanisms proposed for converting the photodissociation products CO and O2 back to CO2.
The possibility of catalytic destruction of H by C2H2 in the Jovian upper atmosphere is investigated, and other photochemical hydrocarbon reactions are presented. It is shown that the catalytic action of C2H2 can destroy or preserve atomic hydrogen, depending on the branching ratio of an intermediate reaction and the temperature dependence of various reaction rates. A model Jovian atmosphere is constructed, and the altitude profiles of some species are plotted. It is noted that this model has a greater atomic hydrogen abundance and a lower concentration of C2H2 than previous ones, and that the H profile should be considered as an upper limit for the Jovian atmosphere.
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