A reinvestigation of the temperature dependence of the rate constant for the reaction O + O2 + M ? O3 + M (for M = O2, N2, and Ar) by the flash photolysis resonance fluorescence technique

1980 ◽  
Vol 12 (7) ◽  
pp. 469-490 ◽  
Author(s):  
Odo Klais ◽  
Philip C. Anderson ◽  
Michael J. Kurylo
Keyword(s):  
Temperature Dependence ◽  
Rate Constant ◽  
Flash Photolysis ◽  
Fluorescence Technique ◽  
Resonance Fluorescence

Rate of the OH + C6H6 + He reaction in the fall-off range by discharge flow and OH resonance fluorescence

1991 ◽  
Vol 69 (7) ◽  
pp. 1057-1064 ◽  
Author(s):  
A. Goumri ◽  
J. F. Pauwels ◽  
P. Devolder
Keyword(s):  
Rate Constant ◽  
Room Temperature ◽  
Flash Photolysis ◽  
Tropospheric Chemistry ◽  
Resonance Fluorescence ◽  
Discharge Flow ◽  
Gas Phase Kinetics ◽  
Radical Adduct ◽  
Fluorescence Reaction ◽  
Two Temperatures

The rate constant k1 of the reaction[Formula: see text]has been investigated by discharge flow resonance fluorescence of OH in the fall-off pressure range. From systematic measurements at five pressures between 0.5 and 9.5 torr, the Troe parameters k0 and k∞ (with Fc = 0.6) have been derived at two temperatures: room temperature and 353 K. For room temperature, (297 ± 3) K, these parameters are k0 = (1.7 ± 0.5) × 10−29 cm6 molecule−2 s−1, k∞, = (10 ± 2) × 10−13 cm3 molecule−1 s−1. Our experimental results are consistent with addition as the dominant path, in agreement with flash photolysis investigations and with the existence of a fast reaction with NO2 of the (OH—benzene) radical adduct. A numerical simulation shows that this latter reaction should have a rate constant of (4 ± 2) × 10−11 cm3 molecule−1 s−1 at 353 K. Key words: gas phase kinetics, discharge flow, resonance fluorescence, reaction of OH with benzene, tropospheric chemistry.

Recombination of iodine atoms in dilute solutions of argon

1970 ◽  
Vol 316 (1524) ◽  
pp. 81-96 ◽  
Keyword(s):  
Experimental Data ◽  
Temperature Dependence ◽  
Rate Constant ◽  
Flash Photolysis ◽  
Quantitative Agreement ◽  
A Value ◽  
Electronically Excited ◽  
Recombination Rate Constant ◽  
Equilibrium Separation ◽  
Combined Data

The reaction 2I + Ar→ I 2 + Ar was studied at 298, 323 and 423 K by flash photolysis. The overall rate constant, k obs , for this reaction is a linear function of [I 2 ]/[Ar], but below [I 2 ]/[Ar] ~ 10 -4 , the relation becomes non-linear and k obs falls below extrapolated values. The fall-off is explained in terms of a mechanism involving an IAr intermediate: I + Ar ⇌ IAr IAr + I → I 2 + Ar. The equilibrium separation in such an IAr complex is 0.55 nm and the binding energy is 6.3 kJ mol -1 (1.5 kcal mol -1 ). This mechanism predicts the onset of the fall-off in agreement with the available experimental data. Moreover, the temperature dependence of this onset and the temperature dependence of the recombination rate constant from 298 to 1500 K are also satisfactorily explained. In addition to the above, the new mechanism yields quantitative agreement between our new rate constants and those reported previously. These combined data for 298 K yield a value of 3.00 (± 0.16) x 10 9 l 2 mol -2 s -1 for the rate constant for the reaction 2I + Ar → I 2 + Ar, and one of 1.00(± 0.09) х 10 12 I 2 mol -2 s -1 for 2I + I 2 → 2I 2 . Several other mechanisms are also considered, including some previously suggested in the literature. It is shown that none of these explains satisfactorily all the experimental data. However, most of the available experimental data could be explained, if it were assumed that the recombination proceeds via an unobserved electronically excited I 2 , formed from two 2 P 3/2 atoms, with a potential well 21 to 29 kJ mol -1 deep (5 to 7 kcal mol -1 ).

Radiolysis studies on the corrosion inhibitors 1 -hexyn-3-ol, cinnamonitrile, and 1,3-diethyl-2-thiourea

1995 ◽  
Vol 73 (12) ◽  
pp. 2137-2142 ◽  
Author(s):  
A.J. Elliot ◽  
M.P. Chenier ◽  
D.C. Ouellette
Keyword(s):  
Hydrogen Atom ◽  
Hydroxyl Radical ◽  
Temperature Dependence ◽  
Rate Constant ◽  
Rate Constants ◽  
Corrosion Inhibitors ◽  
Hydrated Electron

In this publication we report: (i) the rate constants for reaction of the hydrated electron with 1-hexyn-3-ol ((8.6 ± 0.3) × 108 dm3 mol−1 s−1 at 18 °C), cinnamonitrile ((2.3 ± 0.2) × 1010 dm3 mol−1 s−1 at 20 °C), and 1,3-diethyl-2-thiourea ((3.5 ± 0.3) × 108 dm3 mol−1 s−1 at 22 °C). For cinnamonitrile and diethylthiourea, the temperature dependence up to 200 °C and 150 °C, respectively, is also reported; (ii) the rate constants for the reaction of the hydroxyl radical with 1-hexyn-3-ol ((5.5 ± 0.5) × 109 dm3 mol−1 s−1 at 20 °C), cinnamonitrile ((9.2 ± 0.3) × 109 dm3 mol−1 s−1 at 21 °C), and diethylthiourea ((8.0 ± 0.8) × 108 dm3 mol−1 s−1 at 22 °C). For cinnamonitrile, the temperature dependence up to 200 °C is also reported; (iii) the rate constant for the hydrogen atom reacting with 1-hexyn-3-ol ((4.3 ± 0.4) × 109 dm3 mol−1 s−1 at 20 °C). Keywords: radiolysis, corrosion inhibitors, rate constants.

Mechanistic studies of aromatic ketone-sensitized photoreduction of bis(acetylacetonato)copper(II)

1983 ◽  
Vol 61 (5) ◽  
pp. 801-808 ◽  
Author(s):  
Yuan L. Chow ◽  
Gonzalo E. Buono-Core ◽  
Bronislaw Marciniak ◽  
Carol Beddard
Keyword(s):  
Rate Constant ◽  
Rate Constants ◽  
Flash Photolysis ◽  
Decay Rates ◽  
Polynuclear Aromatic Hydrocarbons ◽  
Aromatic Ketone ◽  
Quantum Yields ◽  
Triplet States ◽  
Quenching Rate ◽  
Triplet Energy

Bis(acetylacetonato)copper(II), Cu(acac)2, quenches triplet excited states of ketones and polynuclear aromatic hydrocarbons efficiently, but only aromatic ketones with high triplet energy successfully sensitize photoreduction of Cu(acac)2 in alcohols under nitrogen to give derivatives of aeetylacetonatocopper(I), Cu(acac). For the triplet state benzophenone-sensitized photoreduction of Cu(acac)2, the quantum yields of photoreduction (ΦC) and those of benzophenone disappearance (ΦB) were determined in methanol with various concentrations of Cu(acac)2. The values of the quenching rate constant, kq, determined from these two types of monitors on the basis of the proposed mechanism were in good agreement (6.89 ~ 7.35 × 109 M−1 s−1). This value was higher, by a factor of about two, than that obtained from the monitor of the benzophenone triplet decay rates generated by flash photolysis in the presence of Cu(acac)2. The quenching rate constants of various aromatic ketone and hydrocarbon triplet states by Cu(acac)2 were determined by flash photolysis to be in the order of the diffusion rate constant and the quantum yields of these photoreductions were found to be far from unity. Paramagnetic quenching, with contributions of electron exchange and charge transfer, was proposed as a possible quenching mechanism. For a series of aromatic ketone sensitizers with higher triplet energy, this mechanism was used to rationalize the observed high quenching rate constants in contrast to the low quantum yields of photoreduction.

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