The fluorine atom, being the most electronegative, strongly seeks the more positive nitrogen atom during photolysis. The chlorine atom also apparently prefers the nitrogenbonded configuration, but not as much as fluorine. Bromine, which is less electronegative than oxygen or nitrogen, favors the more negative oxygen atom with photolysis.It is also interesting to note the very small amount of ONOBr formed in the initial matrix deposit. In an earlier account,9 the 1714-cm'1 absorption of ONOC1 was found to be approximately twice as intense as the 1675-cm"1 absorption of C1N02 under identical conditions as the present study, although no quantitative significance could be inferred at that time. Subsequently, Niki et al.,16 in an infrared study of the gas phase reaction of chlorine atoms and N02, estimated that ONOC1 was formed initially at more than four times the rate of C1N02. The agreement between these two reports appears to be excellent. Fluorine atoms have also been shown to react with the oxygen atom of N02 to form ONOF at low temperatures with no activation energy. The present results, however, show very little initial ONOBr formation during matrix condensation, and it is not clear why a barrier to the direct formation of ONOBr should exist.Recently, Molina and Molina17 and Spencer andRowland10 have discounted the role of ONOC1 and ONOBr, respectively, as stratospheric halogen atom sinks because of the measured high photodissociation cross section of ONOC1 in the near-UV17 and the belief10 that ONOBr is not expected to be significantly more stable than ONOC1. The present results clearly show that ONOBr is the most stable of the halogen nitrites with respect to the corresponding nitryl halides. However, it is not clear from our work that ONOBr is more stable than ONOC1 since the photolysis behavior could be easily attributed to the instability of BrN02 as compared to C1N02. On the other hand, the present results certainly do not rule out the possibility that the stability of ONOBr in the presence of near-UV irradiation is greater than the stability of ONOC1.
Ideale Photoanoden für eine wirkungsvolle Photoelektrolyse von H2O mit Sonnenenergie müßten robuste Oxidhalbleiter mit niedriger Elektronenaffinität und Energiebandabständen von weniger als ∼ 2.5 eV sein.
This report describes work carried out on the development of rechargeable, ambient temperature Li/sulfur and Li/metal sulfide batteries. The Li/S system has the cathode material dissolved in the electrolyte, as Li2S n. Tetrahydrofuran, 1M LiAsF6, is one of the more attractive electrolytes discovered for this cell, since it can dissolve up to ^10M S as Li2S n. Despite the oxidative nature of the electrolyte, Li is stable in it and can be electrodeposited from it on battery charge. Passivation of the Li due to insoluble Li +-permeable films is thought to be responsible for this stability. Cells of the configuration Li 5M S(as Li2S n), THF, 1M LiAsFs/carbon can be discharged at 50°C with a utilization of nearly 1.5e"/S at the C/3 rate. This corresponds to our rate-capacity goal for this battery (>50% utilization at C/3) in its proposed vehicular or load-leveling applications. Further improvements in rate are possible with Lewis acidic • catalysts such as
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