A Study of the Reaction of N+ with O2: Experimental Quantification of NO+(a 3∑+) Production (298−500 K) and Computational Study of the Overall Reaction Pathways

Experimental and theoretical study of the reaction of POCl(3) (-) with O(2)

The oxidation of the trichlorooxyphosphorus anion (POCl(3) (-)), which takes place in combustion flames, has been examined experimentally at a variety of temperatures and theoretically via ab initio and density functional methods. The reaction was examined in a turbulent ion flow tube and kinetics was measured between 300 and 626 K, estimating an overall reaction barrier of 1.23 kcal/mol. Calculations at the density functional, Moller-Plesset second order perturbation, and coupled cluster levels of theory with basis sets up to augmented triple-zeta quality point to a multistep reaction mechanism involving an initial [OP(Cl)(3)(OO)](-) intermediate, an adduct between triplet O(2) with POCl(3) (-), subsequent formation of a four-membered nonplanar P-O-O-Cl ring transition state, with concomitant breaking of the P-Cl and O-O bonds to provide a transient intermediate [OP(Cl)(2)OO...Cl](-), which, in turn, converts to the product complex (POCl(2) (-))(ClO) upon formation of the Cl-O bond without barrier. The calculated energy of the four-membered transition state is considered to be in good agreement with the small overall barrier found by experiment. The final step is responsible for the large exothermicity of the reaction.

Reexamination of ionospheric chemistry: high temperature kinetics, internal energy dependences, unusual isomers, and corrections

A number of aspects of ionospheric chemistry are revisited. The review discusses in detail only work performed at AFRL, but other work is mentioned. A large portion of the paper discusses measurements of the kinetics of upper ionospheric reactions at very high temperatures, i.e. the upper temperature range has been extended to at least 1400 K and in some cases to 1800 K. These temperatures are high enough to excite vibrations in O2, N2, and NO and comparing them to drift tube data allows information on the rotational temperature and vibrational level dependences to be derived. Rotational and translational energy are equivalent in controlling the kinetics in most reactions. Vibrational energy in O2 and N2 is often found to promote reactivity which is shown to cause ionospheric density depletions. NO vibrations do not significantly affect the reactivity. In a number of cases, detailed calculations accompanied the experimental studies and elucidated details of the mechanisms. Kinetics of two peroxide isomers important in the lower ionospheric have been measured for the first time, i.e. NOO+ and ONOO-. Finally, two examples are shown where errors in previous data are corrected.