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.

To assess the cycling efficiency of the Li electrode in a positive-limited secondary battery, Li has been plated and stripped from a Li substrate. This has been carried out in a specially designed cell containing a Li electrode of known volume: Li is plated and stripped from this electrode until the substrate is depleted. Individual efficiencies can also be determined from inflections in the stripping curves. Average efficiencies were best for PC, 1M LiAsF6 which had been preelectrolyzed and treated with activated neutral alumina. Here, for 10 C/cm 2 cycles about 85% cycling efficiency was obtained, essentially without Change until the substrate was depleted. In general, LiC104 showed inferior behavior to LiAsF6. * Electrochemical Society Active Member.

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.

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