An extensive evaluation is presented of the available gas phase chemical kinetic rate constants for the interac· tions of the low lying electronic states of several atoms and molecules with numerous collision partners. These include the following excited states: C(2 1 D 2 ,2 1 S o ), N(2 2 D31l,5/2, 2 2 P1I1, 3/2), P(32D3/2,51l,32Pl/2,3/2), S(3 1 D 2 ,3 I S 0 ), Se(4 S P o ' 4 1 D 2 ,4 1 S 0 ), Te(53PI,o,51D2,5ISo)' COCa an, a'3I;+,d aA,e 3I;-,A III), CS(a all, A III), OH(A 2I;+), OD(A 2£+), 02(C lE~,C 3A u .A 3I;~,B 3r;~), and S2(a IAg,b lE;,A ar;~,B ar;~). Wherever possible, recommended values are suggested. Much of the data refers only to room temperature. To facilitate the evaluation, colJision·free radiative lifetimes often have been required. These also have been evaluated and are presented. The mechanisms of the interactions and the various potential kinetic channels are discussed. These include such processes as chemical reactions, electronic quenching to the ground electronic state, electronic cross relaxation to an adjacent excited state, and for molecules, vibrational and rotational relaxation processes within the excited state. A complete coverage of the literature published prior to 1978 has been attempted.
The design of a cathode to operate in an oxygen-rich environment AIP Conf.Measurements of sodium and OH concentrations in ten oxygen-rich H,/O,lN, flames by respective saturated and low-power laser-induced fluorescence techniques have led to a much improved understanding of the complex flame chemistry of sodium in such oxygen-rich media. Previous interpretations have been shown to be largely incomplete or in error. The one-dimensional flame downstream profiles indicate that the amount of free sodium approximately tracks the decay of H atom and as the flame radicals decay sodium becomes increasingly bound in a molecular form. A detailed kinetic model indicates that the sodium is distributed between NaOH, which is dominant, and NaO,. Concentrations of NaO are very small and NaH negligible. The actual distribution is controlled by the temperature, the oxygen concentration, and the degree of nonequilibration of the flames' basic free radicals. Na, NaO, NaO" and NaOH are all coupled to one another by fast reactions which can rapidly interconvert one to another as flame conditions vary. NaO, plays an indispensable role in providing alternate efficient channels by which NaOH can be produced. Its contribution becomes increasingly important at lower temperatures where the flux through the NaO, intermediate becomes dominant over that for the direct reaction between Na and H,O. As a consequence, the ratio of NaOH to Na can become enhanced by up to two orders of magnitude at lower temperatures over what might have been expected from the Na + H,O direct reaction alone. The dissociation energy D~ (Na-O,) is established to be 39±5 kcal mol-I and the value of the rate constant for the Na + 0, + M reaction of 2X 10-28 T-I cm 6 molecule-' S-I for the flame gases. The sodium distribution within the highest temperature, low-O, flame, in which NaOH is dominant and equilibrated, supports a value of D~ (Na-OH) of 78.9±2 kcal mol-I. The rate constants for several reactions of Na, NaOH, NaO" and NaO with flame species have been established approximately. An analysis of the total kinetic scheme shows that the chemical fluxes are carried predominantly by four reactions only. These considered alone, reproduce the data surprisingly well. An analysis of the implications of the corresponding large rate constants for the terrnolecular reaction of the other alkali metals with oxygen suggests that these will undoubtedly show to varying degrees similar behavior to sodium. Values for the bond dissociation energies of the other alkali dioxides are discussed. It appears that in practical combustion systems, even at low temperatures, the conversion of alkali metals to the corresponding hydroxide will not be kinetically constrained and its concentration will be at or in excess of the expected equilibrium value.
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