Ozone produced by discharge or photolysis of oxygen has unusually heavy isotopic composition ((18)O/(16)O and (17)O/(16)O ratio) which does not follow normal mass fractionation rule: δ(17)O ∼ 0.52(*)δ(18)O, expressed as an anomaly Δ(17)O = δ(17)O - 0.52(*)δ(18)O. Ozone molecule being an open isosceles triangle can have the heavy isotope located either in its apex or symmetric (s) position or th...

The dissociation of pentane-2,4-dione radical cation has been studied by ab initio direct classical trajectory calculations at the MP2/6-31G(d) level of theory. A bond additivity correction has been used to improve the MP2 potential energy surface (BAC-MP2). A microcanonical ensemble was constructed using quasiclassical normal-mode sampling by distributing 10 kcal/mol of excess energy above ZPE...

The unimolecular decomposition of the C6H5 radical has been studied by ab initio molecular orbital and statistical-theory calculations. Three low-energy decomposition channels, including the commonly assumed decyclization/fragmentation process yielding n-C4H3 + C2H2, have been identified. With a modified Gaussian-2 method of Mebel et al. (ref 17), the energy barrier for the decyclization of C6H...

The high temperature decomposition kinetics of toluene and benzyl were investigated by combining a kinetic analysis with the ab initio/master equation study of new reaction channels. It was found that similarly to toluene, which decomposes to benzyl and phenyl losing atomic hydrogen and methyl, also benzyl decomposition proceeds through two channels with similar products. The first leads to the...

The multi-channel thermal unimolecular decomposition of glyoxal was experimentally investigated in the temperature range 1106 K < T < 2320 K and at total densities of 1.7 x 10(-6) mol cm(-3) < rho < 1.9 x 10(-5) mol cm(-3) by monitoring HCO (frequency modulation spectroscopy, FMS), (CHO)(2) (UV absorption), and H atom (atom resonance absorption spectroscopy, H-ARAS) concentration-time profiles ...

The potential energy surfaces (PES) for the reaction of the C(2)H radical with 1-butyne (C(4)H(6)) have been studied using the CBS-QB3 method. Density functional B3LYP/cc-pVTZ and M06-2X/6-311++G(d,p) calculations have also been performed to analyze the reaction energetics. For detailed theoretical calculation on the total reaction mechanism, the initial association reactions on more and less s...

The strange mass-independent isotope effect for the enrichment of ozone and the contrastingly unconventional strong mass-dependent effect of individual reaction rate constants are studied using statistical ~RRKM!-based theory with a hindered-rotor transition state. Individual rate constant ratios of recombination reactions and enrichments are calculated. The theory assumes ~1! an ‘‘h-effect,’’ ...

This paper describes ab initio electronic structure calculations on the planar transition states of 2-chloropropene leading to HCl elimination in the ground electronic state to form either propyne or allene as the cofragment. The calculations provide optimized geometries of the transition states for these two reaction channels, together with vibrational frequencies, barrier heights, and reactio...

Time-resolved kinetic studies of the reaction of silylene, SiH2, generated by laser flash photolysis of phenylsilane, have been carried out to obtain rate constants for its bimolecular reaction with O(2). The reaction was studied in the gas phase over the pressure range 1-100 Torr in SF(6) bath gas, at five temperatures in the range 297-600 K. The second order rate constants at 10 Torr were fit...

This work reports the mid-IR spectroscopy and reaction kinetics of 2-methyl-1,3-dioxolane (2M13DO). We carried out spectroscopic measurements to deduce temperature-dependent absorption cross-sections 2M13DO over a broad wavelength range 8.4–10.5 ?m (950–1190 cm?1). For these measurements, we employed rapidly tuning MIRcat-QT™ laser that can be operated either at fixed or scanned mode wide regio...