Energy partitioning in O(¹D₂) reactions. III. O(¹D₂) + NH₃ → OH(v′) + NH₂

Abstract

, 2315 (1986). The vibrational distribution in the OH created by the reaction of O ( ' D 2 ) atoms with NH3 has been recorded directly using low pressure infrared emission spectroscopy. The relative kinetic energy of the reagents is Boltzmann at 300 K. The OH product vibrational levels are populated statistically. indicating that the reaction probably involves a long-lived 0 N H 3 intermediate. There is some evidence that this may not be the case at higher reagent translational energies. 2315 (1986) Faisant appel a la spectroscopie d'emission infrarouge 5 basse pression. on a enregistre directement la distribution vibrationnelle du OH qui est crC6 par la reaction des atomes de O ( ' D , ) avcc le NH3. A 300 K . 1'Cnergie cinktique relative des reactifs est celle de Boltzmann. 11 y a une distribution statistique des niveaux vibrationnels du produit OH et ceci indique que la rkaction implique probablement un interrnkdiare 0 N H 3 posskdant une longue vie. Quelques donnees suggerent que tel ne serait pas le cas 5 des energies de translation des reactifs qui seraient plus elevees.[Traduit par la revue]

Full characterization of OH product energetics in the reaction of O(1D2) with hydrocarbons

“…Instead, the low-J component may arise as the result of dissociation of an RCH 2 0Ht complex in which intramolecular energy transfer has resulted in the equipartition of reaction exoergicity. Although equilibration of heavier complexes is expected to playa relatively more important role in comparison to prompt dissociation because of the presence oflow-frequency modes that enhance the efficiency of intramolecular energy transfer, the overall efficiency for OH production in reaction (6) should drop due to competition with the channel that leads to C-C bond scission in reaction (7). That hypothesis is in qualitative agreement with observation (Table II).…”

“…In order to test whether the low-J component deconvoluted from the observed product distribution might result from the dissociation of a long-lived intermediate complex, a general purpose computer program was used to calculate relative RRKM unimolecular rate coefficients, ka (E *), 5S for processes (6) and (7), the energetics of which are schematically outlined in Fig. 15.…”

“…The principal mechanism for the 0* /RH reaction was initially unraveled by Cvetanovic and co-workers 2 and later confirmed by others 30 in conventional continuous photolysis experiments, in which the pressure dependence of final products was monitored as a function oftime and initial experimental conditions. Those pioneering studies revealed that the principal mechanism for 0* /RH reaction involves the insertion of the oxygen atom into a C-H bond to yield a chemically activated alcohol (4) At sufficiently high pressure, that intermediate species could be collision ally stabilized prior to subsequent dissociation RCHzOHt + M ..... RCH 2 OH + M. (5) Ordinarily, such collisional stabilization would not occur, however, and dissociation of the C-O bond RCHzOHt ..... RCH2 +OH or a weaker C-C bond RCH20Ht-R + CH 2 0H (6) (7) would dominate. Clearly, reaction (7) does not pertain to the case of R = H. Additionally, the chemically activated complex could dissociate to yield molecular hydrogen 31 ,32 RCHzOHt ..... RCH=O + H 2 •…”

The OH-yield in the reaction of O(1D) + CH4 under high pressure conditions up to 560 bar helium

“…It is well known that in the two reactions about 70% of the OH-radicals formed are vibrationally excited and their vibrational distributions are quite similar [31,32]. The increase in intensity for both fluorescence-yield time profiles is almost identical indicating comparable relaxation kinetics.…”

“…However, this procedure demands a detailed knowledge of the reactive part of the potential energy surface which may be rather difficult to obtain. In the case of chemically activated methanol from reaction (1c) the situation is very complicated due to the competition between the different decomposition channels (2a) to (2f) [23,24].…”