13587-54-7Relevant academic research and scientific papers
Isotope effects in the deactivation of O( 1 D) atoms by XCl and XF (X=H,D)
Chichinin
, p. 425 - 432 (2000)
The method of time-resolved laser magnetic resonance (LMR) was used to study the deactivation of O(1D) by HCl, DCl, HF, and DF at room temperature. For O(1D)+XF(X=H,D), the effect of deuteration on the rates of physical quenching and
A new mechanism for the enhancement of activated bimolecular reactions by rotational excitation
Miklavc, Adolf,Perdih, Marko,Smith, Ian W.
, p. 8813 - 8818 (2000)
The kinematic mass model (KMM), which has been developed to examine the dynamics of activated bimolecular reactions, has here been adapted to examine how orientational effects associated with reagent rotation influence the rotational state dependence of reaction cross-section. It is shown that, for reactions where the critical dividing surface (CDS) and the equipotential contours near to the CDS are prolate, i.e., elongated in the direction of the longitudinal molecular axis, rotation favors impact on the CDS near collinear geometries where the barrier to reaction is least, with the result that reaction cross-sections are enhanced with increasing reagent rotation. In the case of the rotational velocity being comparable with, or greater than, the relative translational velocity, this enhancement can greatly exceed that due to part of the rotational energy being available for barrier crossing. The KMM model, allowing for this orientational effect, has been applied to the reactions O+HCl (DCl) and O+H2 on well-known model potential energy surfaces (PESs) where both the CDSs and the equipotential contours near the CDS are prolate. The results agree well with those from trajectory calculations. The role of the above effects of reagent rotation in the case of surfaces of nonprolate shapes is discussed qualitatively.
Dissociative recombination of H+ (H2 O)3 and D+ (D2 O)3 water cluster ions with electrons: Cross sections and branching ratios
Oejekull, J.,Andersson, P. U.,Naagaard, M. B.,Pettersson, J. B. C.,Markovic, N.,et al.
, p. 1 - 8 (2009/12/02)
Dissociative recombination (DR) of the water cluster ions H+ (H2 O)3 andD+ (D2 O)3 with electrons has been studied at the heavy-ion storage rin g CRYRING (Manne Siegbahn Laboratory, Stockholm University). For the first time, absolute DR cross sections have been measured for H+ (H2 O)3 inthe energy range of 0.001-0.8 eV, and relative cross sections have been measured for D+ (D2 O)3 in the energy range of 0.001-1.0 eV. The DR cro ss sections for H+ (H2 O)3 are larger than previously observed for H+ (H2 O)n (n=1,2), which is in agreement with the previously observed trend indicating that the DR rate coefficient increases with size of the watercluster ion. Branching ratios have been determined for the dominating p roduct channels. Dissociative recombination of H+ (H2 O)3 mainly resultsin the formation of 3 H2 O+H (probability of 0.95±0.05) and with a possible minor channel resulting in 2 H2 O+OH+ H2 (0.05±0.05). The dominating channels for DR of D+ (D2 O)3 are 3 D2 O+D (0.88± 0.03) and 2 D2 O+OD+ D2 (0.09±0.02). The branching ratios are comparable to earlier DR results for H+ (H2 O)2 and D+ (D2 O)2, which gave 2 X2 O+X (X=H,D) with a probability of over 0.9.
Reaction of hydroxyl radical with nitric acid: Insights into its mechanism
Brown, Steven S.,Burkholder, James B.,Talukdar, Ranajit K.,Ravishankara
, p. 1605 - 1614 (2007/10/03)
The rate constant for the reaction of hydroxyl radicals with nitric acid has an unusual pressure and temperature dependence. To explore the mechanism for this reaction, we have measured rate constants for reactions of isotopically substituted species OD+DNO3, OH+DNO3, OD+HNO3, and 18OH+HNO3 and the yield of NO3 product. Deuterium substitution on nitric acid results in more than a 10-fold reduction in the rate constant, removes the pressure dependence (over the observed range of 20-200 Torr in He and SF6), and leads to a strongly curved Arrhenius temperature dependence. Deuterium substitution on hydroxyl increases the rate constant slightly but does not change the pressure dependence. There is no evidence for exchange reactions in the isotopically mixed reactions. Absorption measurements of the NO3 product yield show that the title reaction produces nitrate radical with unit efficiency over all temperatures and pressures studied. We discuss the implications of the measured rate constants, product yields, and lack of isotopic exchange in terms of a mechanism that involves formation of a hydroxyl radical-nitric acid complex and its subsequent reaction to give NO3 and H2O.
Photoinitiated H- and D-atom reactions with N2O in the gas phase and in N2O-HI and N2O-DI complexes
Boehmer, E.,Shin, S. K.,Chen, Y.,Wittig, C.
, p. 2536 - 2547 (2007/10/02)
Reactions of H atoms with N2O have two product channels yielding NH + NO and OH + N2.Both channels were observed via NH A3Π X3Σ and OH A2Σ X2Π laser-induced fluorescence spectra.Photoinitiated reactions with N2O-HI complexes yield a much lower / ratio than under the corresponding bulk conditions at the same photolysis wavelength.For hot D-atom reactions with N2O, this effect is somewhat more pronouced.These results can be interpreted in terms of entrance channel geometric specificity, namely, biasing hydrogen attack toward the oxygen.Another striking observation is that the OH and OD rotational level distributions (RLD) obtained under bulk conditions differ markedly from those obtained under complexed conditions, while the NH as well as the ND RLD are similar for the two environments.In addition, OH Doppler profiles change considerably in going from bulk to complexed conditions, while such an effect is not observed for NH.The changes observed with the OH RLD are most likely due to OH-halogen interactions and/or entrance channel specificity.Under bulk conditions, the Doppler shift measurements indicate a large amount of N2 internal excitation (i.e., ca. 25 000 cm-1) for the OH (Υ = 0) levels monitored.This is consistent with a reaction mechanism involving an HNNO intermediate.The hot hydrogen atom first attaches to the terminal nitrogen of N2O and forms an excited HNNO intermediate having a relatively elongated N-N bond compared with N2O.Then the H atom migrates from nitrogen to oxygen and exits to the N2 + OH product channel, leaving N2 vibrationally excited.A simple Franck-Condon model can reconcile quantitatively the large amount of N2 vibrational excitation.
Rate Constants for Reactions D * D2O -> D2 * OD by the Flash Photolysis-Shock Tube Technique over the Temperature Range 1285 - 2261 K: Results for the Back-Reaction and a Comparison to the Protonated Case
Fisher, J. R.,Michael, J. V.
, p. 2465 - 2471 (2007/10/02)
The absolute rate constant for the reaction of D atoms with deuterium oxide, D + D2O -> D2 + OD, has been measured by using the flash photolysis-shock tube (FP-ST) technique.D atoms are monitored by atomic resonance absorption spectroscopy (ARAS) using LyαD lamp.The results, obtained over the temperature range 1285 - 2261 K, can be represented by the Arrhenius expression k = (2.90 +/- 0.73) * 1E-10 exp(-10815 +/- 356 K/T) cm3 molecule-1 s-1.The experimental results have been compared with results from the analogous protonated case, and an isotope effect of unity is indicated within experimental error.The rate constant for the back-reaction, OD + D2, calculated through the equilibrium constant, is k = (6.6 +/- 1.7) * 1E-11 exp(-3320 +/- 356 K/T) cm3 molecule-1 s-1, over the same temperature range, 1285 - 2261 K.Theoretical rate constants, based on a new potential energy surface by Kraka and Dunning, are calculated with conventional transition-state theory for both D + D2O and H + H2O.Similar calculations for both back-reactions are presented, and the theoretical calculations are compared to the experimental results.
An Experimental Study of the Reactions of OH Radicals with 1,3-Butadiyne, Propyne, 1-Butyne and 2-Butyne in the Gas Phase
Bartels, M.,Heinemann-Fiedler, P.,Hoyermann, K.
, p. 189 - 208 (2007/10/02)
The reactions of OH/OD radicals with butadiyne, propyne, 1-butyne and 2-butyne have been studied at low temperature (295 K) in low pressure reactors (0.1-15 mbar).Samples were withdrawn continuously by a molecular beam device and analyzed by a mass spectrometer.The detection sensitivity was enhanced by modulation techniques and single ion counting.The primary reaction products are described mainly by an addition mechanism.For the reaction of butadiyne with OH radicals the mechanism and a rate constant of 1.2(+/-0.6)E13 cm3/mol s were found.The reactions of the adduct with the alkynes were found to be very fast.Complementary studies of the reactions of H/D + C4H2 and F + C4H2 are reported. - Keywords: Chemical kinetics / Elentary reactions / Mass spectrometry
Kinetic and mechanistic investigations of F + H2O/D2O and F + H2/D2 over the temperature range 240-373 K
Stevens, Philip S.,Brune, William H.,Anderson, James G.
, p. 4068 - 4079 (2007/10/02)
The rate constants for the reactions of fluorine atoms with H2O and D2O have been determined over the temperature range 240-373 K by using a discharge flow system at 1-2 Torr of total pressure. F atoms were detected by chemical conversion with deuterium. The resulting D atoms were detected by atomic resonance scattering. The rate constants are k1 = (1.6 ± 0.3) × 10-11 exp[(-28 ± 42)/T] cm3 molecule-1 s-1 for F + H2O → HF + OH and k2 = (8.4 ± 1.2) × 10-12 exp[(-260 ± 110)/T] cm3 molecule-1 s-1 for F + D2O → DF + OD. The reported error limits are at the 95% confidence level. The reactions F + H2 → HF + H (k3 = (1.2 ± 0.1) × 10-10 exp[(-470 ± 30)/T] cm3 molecule-1 s-1) and F + D2 → DF + D (k4 = (9.3 ± 1.1) × 10-11 exp[(-680 ± 50)/T] cm3 molecule-1 s-1) were also studied over the same temperature range. The rate constants for the latter reactions are in excellent agreement with previous studies. The low activation energy and A factor for the F + H2O/D2O reactions, as well as the slightly enhanced kinetic isotope effect (3.9 at 298 K), suggest a tunneling mechanism for these reactions, and thus the mechanistic interpretation of this system requires some knowledge of the potential energy surface at the microscopic level. Ab initio calculations on this system predict a classical barrier height of approximately 10 kcal/mol, while a semiempirical BEBO calculation predicts a barrier height of a one-dimensional tunneling model. With use of the theoretical implications in conjunction with the experimental evidence, a potential energy surface has been calculated for this reaction that leads to better agreement with the experimental results. The best-fit prediction of the observed activation energy and kinetic isotope effect suggest that the mechanism for this reaction involves tunneling through a classical barrier height of approximately 4 kcal/mol.
Energy disposal in the reactions O(1D) + NH3 -> OH + NH2 and O(1D) + ND3 -> OD + ND2
Cordova, Jose F.,Rettner, Charles T.,Kinsey, James L.
, p. 2742 - 2748 (2007/10/02)
Further investigations of the reaction O(1D) + NH3 -> OH + NH2 and the first results on the reaction O(1D) + ND3 -> OD + ND2 are reported.The OH and OD rotational distributions have been found to be statistical.Hotter than statistical vibrational distributions are measured.The spin state distribution is statistical, with a strong preference to populate the energetically lower Λ component in both spin states.A preliminary study of the NH2 product shows very little rotational excitation.An analysis of this radical's vibrational hot bands was not carried out due to lack of detailed spectroscopic information.The total energy is found to be partitioned according to R(OH)> ca. 0.1, V(OH)> ca. 0.25, R(NH2)> ca. 0.04, and T> ca. 0.25.
CHEMICAL REACTIONS OF H AND D ATOMS WITH NO2 AND CINO, A CROSSED MOLECULAR BEAM STUDY.
Haberland,von Lucadou,Rohwer
, p. 507 - 513 (2007/10/02)
The chemical reactions of H and D atoms with NO//2 and CINO have been studied at a collision energy E equals 0. 44 eV (42 kJ/mol) in a crossed molecular beam experiment. Velocity and angular distributions were measured and are used to construct the center of mass (CM) distributions. The earlier reported isotope effect of the angular distributions for H, D plus NO//2 is shown to be due to the different CM to LAB conversions. The CM angular distribution is nearly isotropic for H plus NO//2, but shows strong backward peaking for H plus CINO. The measured translational energy spectra are in agreement with recent fluorescence and chemiluminescence results. The reaction H plus NO//2 proceeds via a long lived intermediate complex, while H plus CINO is a direct reaction.
