The discovery of an orange flame is reported that appears also at higher pressures of active nitrogen and oxygen without the presence of a metal catalyst unlike previous research in over 30 years. Enhancement of emissions of the first positive band system of nitrogen was observed from various vibrational levels of the N2(B 3Πg) state. Arguments to identify the species responsible and implications to previous research of this phenomenon of homogeneous excitation and collisional intersystem crossing into N2(B 3Πg) induced by excited O2 are presented. Its probing for lasing is suggested.

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Silyl radicals and methylsilyl radicals formed by Hg (63Pi)-photosensitized decomposition of silane and methylsilane, respectively, react efficiently with nitric oxide to produce siloxanes and nitrous oxide as the principal products. The reaction is a chain reaction at room temperature which, from the evidence at hand, is proposed to involve SiH80(SiH20)" and CH3SiH20(CH3SiH0)" radicals, in = 0,1, 2, .. .), as well as the primary radicals SiH8 and CH3SiH2.It has previously been reported from this laboratory that, when nitric oxide at low concentration is employed at room temperature as a scavenger of methyl radicals, trimethylhydroxylamine is the stable product of the radical-scavenging process and is formed by the successive addition of methyl radicals to nitric oxide.2•8 Recent studies of the mercury-photosensitized decomposition of monosilane4•5 have suggested that the formation of the predominant silicon-containing product, disilane, may occur via the combination of silyl radicals, viz. SiH3 + SiH3 -> Si2He(1) and, in this respect, at least, may resemble mechanistically the analogous ethane formation in systems containing methyl radicals. However, despite this sim-

Once the initial transients have died out, the rate constant for the dissociation or recombination of a dilute diatomic gas bears the same kind of relationship to individual translation-vibration transition probabilities as does the conductance of a generalized resistance network to the individual resistance components. Thus, it is not possible to single out any one transition which "controls" the rate of dissociation or recombination.Une fois que les phknomenes initiaux ont disparu, la constante de vitesse de la dissociation ou de la recombinaison d'un gaz diatomique diluk apporte le mEme genre de relation aux probabilitks de transition individuelle translation-vibration que ne le fait la conductance d'un rkseau gtnkralist de rksistances aux rksistances composantes individuelles. Ainsi, il n'est possible d'isoler aucune transition qui "contrble" la vitesse de dissociation ou de recombinaison. Canadian Journal o f Chemistry, 49,2617 (1971)In Part 111' of this series (I), it was shown empirically that the rate constant for the dissociation (or recombination) of a diatomic gas can be determined by finding the numerically smallest eigenvalue dn-, of a submatrix A,, of the relaxation matrix. The off-diagonal elements of A,, are simply the specific transition rates Wij (= ZPij) between all the bound states, and each diagonal element is the negative sum of the specific dissociation rate from that state and all the other elements in the row (eq. I11 (5)). The eigenvalue dn-, is related to the desired rate constants through eqs. I11 (21) and I11 (22) viz.-'dn-, where K is the equilibrium constant and [M.] is the inert gas concentration. The minuteness of the inaccuracies of these two relationships is now well established (1-3).Also in Part 111, we found considerable circumstantial evidence for the existence of some kind of bottleneck in the dissociation process: the two most compelling points were that an increase of a factor of 1000 in the dominant bound-continuum rate coefficient caused only a 5% increase in the rate of dissociation; and that when sets of transition probabilities were chosen 'Equations in this paper are designated by a prefix 111; the reader is referred to refs. 1 and 2 for further clarification of the symbols used. which did not have this property, the rate constant for recombination changed its behavior completely from a slow decline with increasing temperature to a very rapid increase with increasing temperature (Fig. 111 (3)). An attempt was made to define the bottleneck by determining which pair of transition probabilities Pij and Pji perturbed the eigenvalue dn-, (i.e. the rate constant) the most; it was found that with the particular set of transition probabilities chosen, this criterion characterized the bottleneck as being somewhat diffuse, extending approximately over the levels v = 9 to v = 13 in H,, with the v = 10 * 11 and v = 11 o 12 transitions the most important contributors.In this Note we examine, by numerical experiment, the sensitivity of the rate constant for the recombination of ...

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