The rates of the reactions OH with CO, C2H4 and C2H2 have been determined between 210 K 460 using time-resolved resonance absorption to monitor removal radicals following their creation by flash photolysis mixtures containing H2O or N2O + H2. At 300 K, rate constant, k6, for CO → CO2+ H (6) is 8.7 × 1010 cm3 mol–1 s–1; k6 shows a slight positive temperature dependence, but Arrhenius plot appears be slightly curved. nature path this reaction discussed results transition state calculations are...

An entirely new experimental method is described which enables the rate constants of neutral–neutral gas-phase reactions to be measured at ultralow temperatures. The measurements are made by applying pulsed laser photolysis (PLP), laser-induced fluorescence (LIF) technique studying kinetics free radical in ultracold environment provided gas flow a Cinétique de Réaction en Ecoulement Supersonique Uniforme (CRESU) apparatus. some detail and its application limitations discussed. Results...

Because of their importance in atmospheric and combustion chemistry, the rate coefficients mechanisms gas-phase reactions OH radical have been studied extensively, kinetic database for these is unsurpassed. The has a rather large electric dipole moment (1.668 D) clearly capable forming strong hydrogen bonds. In this article, we examine evidence such interactions OH. We propose that with alkanes HNO3 represent extremes behavior, no effect bonding first case but reaction via strongly bound...

Infrared chemiluminescence has been observed from vibrationally excited CO, formed in the reaction, O + CS ? CO S. The quenching of overtone spectrum studied as a function concentration each number added gases. A steady-state treatment is developed which allows rates to be determined for de-excitation individual vibrational levels (4 </= nu 13) by He, (nu = 0), NO, N(2), O(2), OCS, N(2)O, and CO(2). experimental results are compared with theoretically predicted rates. Finally, importance...

Experimental studies of gas-phase chemical reactions and molecular energy transfer at very low temperatures between electrically neutral species are reviewed. Although work collisionally induced vibrational rotational is described, emphasis placed on recent results the rates free radical obtained by applying pulsed laser photolysis (PLP)-laser-induced fluorescence (LIF) technique in a CRESU (Cinétique de Réactions en Ecoulement Supersonique Uniforme) apparatus as 13 K. These measurements...

Studies of gas-phase processes at temperatures down to 10 K have recently blossomed, largely through application the CRESU (cinétique de réaction en ecoulement supersonique uniforme) technique. The results are considerable relevance synthesis molecules in dense interstellar clouds, demonstrating that models developed explain observed molecular abundances must be expanded include reactions between electrically neutral species. In addition, experimental stimulated theoretical efforts describe...

A CRESU (Cine′tique de Re′action en Ecoulement Supersonique Uniforme) apparatus has been used to measure rate constants for the reactions of ethynyl radical (C2H) with O2, C2H2, C2H4 and C3H6 at temperatures from 295 down 15 K. C2H radicals are generated by photolysis C2H2 193 nm using an ArF excimer laser reaction rates determined observing chemiluminescence CH(A2Δ) which is in a minor channel between O2. The all four increase as temperature lowered, those unsaturated hydrocarbons exceed...

Advances in experimental techniques, especially the development of CRESU (Cinétique de Réaction en Ecoulement Supersonique Uniforme) method, allow many gas-phase molecular processes to be studied at very low temperatures. This Review focuses on reactions and atomic radicals with neutral molecules. Rate constants for almost 50 such have been measured temperatures as 13 K by using method. The surprising demonstration that so between electrically species can extremely rapid these has excited...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTReaction between hydroxyl (deuteroxyl) radicals and carbon monoxide at temperatures down to 80 K: experiment theoryMichael J. Frost, Paul Sharkey, Ian W. M. SmithCite this: Phys. Chem. 1993, 97, 47, 12254–12259Publication Date (Print):November 1, 1993Publication History Published online1 May 2002Published inissue 1 November 1993https://pubs.acs.org/doi/10.1021/j100149a027https://doi.org/10.1021/j100149a027research-articleACS PublicationsRequest...

Rate coefficients for the reactions N + OH → NO H (1) and O O2+ (2) have been determined, in direct experiments, from 250 to 515 K. A discharge-flow system is used generate measured concentrations of or O; then radicals are formed by flash photolysis H2O monitored resonance fluoresence as they removed reaction under pseudo-first-order conditions. The results fitted rate expressions: k1=(2.21 ± 0.18)×10–10T–0.25 0.17 cm3 molecule–1 s–1, k2=(6.65 0.23)×10–10T–0.50 0.12 s–1 where errors...

The rates of the reactions OH with H2, D2, HCl and DCl have been determined between 210 460 K using time-resolved resonance absorption to monitor removal following creation radicals by flash photolysis mixtures containing H2O or N2O + H2. Arrhenius rate laws are obeyed all four these throughout this range temperature: kOH H2= 1.8 × 10–11 exp[–19.4 kJ mol–1/RT] cm3 molecule–1 s–1, D2= 1.25× exp[–21.5 HCl= 4.1 10–12 exp[–4.4 DCl= 4.7 exp[–6.5 s–1.

Abstract Methods are described for including the participation of bound electronically excited states in calculations on radical recombination reactions. These methods illustrated by applying them to reactions For O 2 , accurate ab initio potentials used which show that electronic degeneracy and long‐range part potential likely be crucial determining contribution a given state overall reaction, as long is not so weakly it dissociates thermally before being quenched. Weak collision effects...

The intensity of HF (and DF) infrared chemiluminescence from vibrationally excited molecules produced in the chain reaction H + F2 → F; F H2 its deuterium analogue) has been studied as a function concentration added CO2 and HF. Using steady-state analysis rate coefficients have determined for transfer vibrational energy (v ≤ 5) DF 3) to (vibrationally cold) results are discussed terms possible mechanisms importance processes chemical lasers.

The competitive processes that result in elimination/pruning of developing synapses are incompletely understood. Serial electron microscopy was used to image postnatal mouse neuromuscular junctions where elimination is well studied and events at every synaptic contact can be examined. Glial or Schwann cells (SCs) shown have two activities during elimination: their separate nerve terminals from each other the muscle fiber; they plaque acetylcholine receptors, apposing this surface as closely...

Significance Refinement of synaptic connections occurs throughout the nervous system and is essential for its proper function. Significant gaps remain in our understanding mechanisms that mediate pruning connections—a form plasticity known as synapse elimination. Recently it has become clear there significant glial cell involvement. The present study rodent neuromuscular junction addresses two outstanding questions involving this involvement: which molecules determine Schwann behavior during...

A CRESU (Cine′tique de Re′action en Ecoulement Supersonique Uniforme) apparatus has been used to measure rate coefficients for the reactions of ground-state carbon atoms, C(3P), with C2H2, C2H4, C3H6 and O2 at temperatures from 295 down 15 K. C(3P) atoms were generated by photolysis C3O2 193 nm using an ArF excimer laser reaction rates determined observing chemiluminescence NO(B2Π) which is in between NO2. The all four increase as temperature lowered, those unsaturated hydrocarbons exceed...