- Determination of absolute thermal rate costants for the charge-transfer reaction DBr+(2Πi,v+) + HBr -> HBr+(2Πi,v'+) + DBr
-
The charge-transfer reaction DBr+(2Πi,v+,J+) + HBr -> HBr+(2Πi',v'+,J'+) + DBr is studied in a state-to-state manner under thermal conditions in a slowly flowing gas mixture of HBr and DBr.The DBr+ reagent is prepared in a selected vibronic level by using (2 + 1) resonance-enhanced multiphoton ionization.The HBr+ product is detected in a quantum-state-specific manner using laser-induced fluorescence.From the measurements of the molecular density and the populations of both HBr+ product and DBr+ reagent, the absolute thermal rate constants k(i,v+ -> i',v'+) are determined for this charge-trasfer process.The rate constants for near-resonant charge transfer in which Δv+ = 0 ad Δi = 0 are much larger than charge-transfer channels in which either Δi0 or Δv+0; the smallest rate constants are for those channels in which both Δi0 and Δv+0.The rotational distribution of the HBr+(i',v'+) product fits a temperature well in each case.For near-resonant charge trasfer, the rotational temperature is slightly warmer than thermal, whereas for nonresonant charge transfer, the rotational temperature is much hotter than thermal.A model in which the excess energy of a charge-transfer process is statistically partitioned among all the degrees of freedom of the complex is able to predict closely the observed rotational temperature.
- Xie, Jinchun,Zare, Richard N.
-
-
Read Online
- Low-temperature Kinetics of the Charge- and Atom-Transfer Reactions (Br+, HBr+ [2∏i, ν+, DBr+ [2∏i, ν+]) + (HBr, DBr) → (HBr+, DBr+, H2Br +, D2Br+, HDBr+)
-
The charge- and atom-transfer reactions between Br+, HBr +, and DBr+ ions and HBr and DBr molecules have been studied in a HBr + DBr + He free jet. The ionic reactants in specific internal states were prepared by resonance multiphoton ionization of either HBr or DBr, and the ionic products were analyzed by mass spectrometry. A set of eight energetically possible reactions was considered in each case, including ions born in near-resonant ionization and photodissociation processes. Kinetic equations were integrated numerically over the appropriate reaction time and an optimization problem was solved to determine rate coefficients fit to final fractions of all ions measured in an experiment. Analytical expressions for the final fractions also were obtained and were used to derive the rate coefficients more accurately. The work is an example of a multireaction study without direct observation of all the reaction products.
- Belikov, Andrey E.,Smith, Mark A.
-
p. 3447 - 3456
(2007/10/03)
-
- Matrix reactivity of AlF and AlCl in the presence of HCl and HBr: Generation and characterization of the new Al(III) hydrides HAlFCl, HAlFBr, and HAlClBr and the monomeric mixed Al(III) halides AlX2Y (X, Y = F, Cl, or Br)
-
The spontaneous and photolytically induced reactions of AlF and AlCl in the presence of HCl and HBr in solid argon matrices were followed and the products identified and characterized by means of IR spectroscopy. Quantum mechanical calculations allow for a further evaluation of the properties of the reaction products. These are the adducts AlF·HCl, AlF·HBr, and AlCl·HBr, representing the products of spontaneous reactions, and the trivalent Al(III) hydrides HAlFCl, HAlFBr, and HAlClBr, which were formed upon photoactivation of these complexes. All three hydrides are planar molecules (Cs symmetry) with bond angles in agreement with the predictions of the VSEPR theory. In addition, the mixed halides AlFCl2, AlFBr2, and AlClBr2 were formed upon photolysis. The bisadducts AlF·(HCl)2 and AlF·(HBr)2 are likely to be the precursors to these species.
- Himmel, Hans-Joerg,Bahlo, Jan,Haussmann, Michael,Kurth, Fabian,Stoesser, Gregor,Schnoeckel, Hansgeorg
-
p. 4952 - 4960
(2008/10/08)
-
- Kinetic study of the reactions of Br with HO2 and DO2
-
The kinetics of the reactions of Br atoms with HO2 and DO2 radicals, Br + HO2 → HBr + O2 (1), and Br + DO2 → DBr + O2 (3), have been studied by the mass spectrometric discharge-flow method at temperatures between 230 and 355 K and at a total pressure of 1 Torr of helium. The rate coefficients measured under pseudo-first-order conditions in excess Br yield the following Arrhenius expressions: k1 = (4.9 ± 0.7) × 10-12 exp[-(310 ± 40)/T] and k3 = (1.9 ± 0.4) × 10-12 exp[-(540 ± 60)/T] cm3 molecule-1 s-1 (uncertainties are 2σ). The k3 value is measured for the first time and that of k1 is compared with those from previous studies.
- Bedjanian, Yuri,Riffault, Véronique,Bras, Georges Le,Poulet, Gilles
-
p. 573 - 578
(2007/10/03)
-
- Kinetics and mechanism of the OH and OD reactions with BrO
-
The kinetics and mechanism of the reactions OH + BrO → products (1) and OD + BrO → products (2) have been studied in the temperature ranges of 230-355 K and 230-320 K, respectively, and at total pressure of 1 Torr of helium using the discharge-flow mass s
- Bedjanian, Yuri,Riffault, Veronique,Le Bras, Georges,Poulet, Gilles
-
p. 6154 - 6166
(2007/10/03)
-
- Photolysis of argon matrices containing tribromoboron and dihydrogen: Synthesis of hydroboranes via dibromoboron
-
Ultraviolet irradiation (λ = 254 nm) of argon matrices containing BBr3 and high concentrations of H2 produces an intermediate, BBr2, which reacts with H2 to form HBBr2, H2BBr, and HBr. The intermediate is completely destroyed by irradiation at 680 nm, the position of a broad absorption band, producing the same hydrogenation products that form by using ultraviolet radiation. The reaction of BBr2 with HD gives HBr and DBBr2 1.6 times more readily than DBr and HBBr2. The spectrum of BBr2 has been reported earlier; herein we reassign the totally symmetric B-Br stretching mode to a weak band at 551.0 cm-1. There is no evidence that either BBr2 or BBr3 forms a ground-state complex with hydrogen in spite of the fact that BBr2 forms more readily in the presence of H2 and that it is readily converted into HBBr2 and H2BBr by H2. However, a complex of hydrogen and BBr2 in its first excited state may lead to the hydrogenation products. The yield of H2BBr is greatest when the concentration of hydrogen in the matrix is greater than about 10 mol %. Both hydrogen atoms that make up the H2BBr come from the same molecule of hydrogen. Mixtures of H2 and D2 give H2BBr and D2BBr with only a trace of HDBBr whereas matrices containing HD produce only HDBBr.
- Moroz, Antoni,Sweany, Ray L.
-
p. 5236 - 5242
(2008/10/08)
-
- Temperature dependence of the rate constants for the H + Br2 and D + Br2 reactions
-
The rate constants for the reactions of H + Br2 and D + Br2 were measured by employing a pulse radiolysis-resonance absorption technique.The rate constants could be expressed by the following Arrhenius equations between 214 and 295 K: k(H + Br2) = 6.7 x 10-10 exp( - 680/T), k(D + Br2) = 6.0 x 10-10 exp( - 720/T), in units of cm3 s-1.Sudden transition state theoretical calculations were performed on the basis of modified LEPS surfaces.The calculated results were compared with the experimental ones.
- Wada, Youichi,Takayanagi, Toshiyuki,Umemoto, Hironobu,Tsunashima, Shigeru,Sato, Shin
-
p. 4896 - 4899
(2007/10/02)
-
