Deuterium as an Indicator of Mechanism in the Photo-Decomposition of Ammonia

Abstract

By studying the photolysis of ammonia-deuterium mixtures it has been experimentally demonstrated that the reaction NH2+H = NH3 is an important feature of the overall photo-decomposition and provides one reason for the low quantum yield observed in the photo-process. It has further been shown that the interaction of hydrogen atoms with ammonia molecules is a process of low efficiency at room temperatures.

Heavy hydrogen as an indicator of the course of chemical reactions

“…In some instances the use of heavy hydrogen as an indicator has merely served to establish a mechanism for which substantial, albeit not conclusive, evidence already existed. Such was the case in the work of Taylor and Jungers (2) on the photodecomposition of ammonia. The initial process in this decomposition may be represented by the equation…”

“…It is not within the scope of this paper to discuss these in detail. This has already been done adequately by Urey and Teal (2). It will suffice for our purposes to mention three factors, one or more of which are operative in many reactions.…”

EXPERIMENTAL TECHNIQUE IN PHOTOCHEMISTRY1

“…Taylor and Jungers (46) mixed deuterium with ammonia and mercury vapor and subjected the mixture to illumination with the resonance radiation at 2536 Á. Deuterium entered the ammonia under the influence of the radiation, and the results showed that the low quantum yield obtained in the photolysis of ammonia is due to the recombination of hydrogen atoms and the NH2 radicals formed by the photochemical reaction.…”

Recherches sur la Photolyse de l'Ammoniac

“…Du tableau de la page 11, nous obtenons pour <Il a la temperature de 197 0 : <Il == <Ilr<P o === 2,38 X 0,2 = 0,479. D'apres (8) ceci correspond a p === 0,298, d'ou 0,298Les valeurs de p calculee theoriquement a partir de(9) et les valeurs experimentales obtenues par l'mterrnediaire de(8) sont consignees dans .le tableau suivant : . 6, nous avons trace la courbe theorique de <I> en fonction de la temperature et porte les points trouves experirnentalement, L' accord existant entre la theorie et l'experience justifie ainsi les differentes hypotheses que nous avons ete amenes a introduire au cours de ce raisonnement.…”