- Direct measurements of C3F7I dissociation rate constants using a shock tube ARAS technique
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This work presents the first direct experimental study on the thermal unimolecular decomposition of n-C3F7I. Experiments were performed behind incident and reflected shock waves using the atomic resonance absorption spectroscopy (ARAS) technique on a resonant line of atomic iodine at 183.04?nm. The reaction C3F7I?+?Ar?→?C3F7?+?I?+?Ar?(1) was studied at specific temperature (800–1200?K) and pressure (0.6–8.3?bar) ranges. Under experimental conditions, the obtained values of the rate constant at temperatures below 950?K are close to the high-pressure limit; however, considering theoretical calculations, the influence of pressure on the rate constant at elevated temperatures remains noticeable. The resulting value of the experimental rate constant of reaction 1 is presented in the following Arrhenius form: 1st(±30%) = 1.05×1014 exp(?200.4kJ?mol?1∕)(s?1). Experimental data were found to correlate with the results of the Rice–Ramsperger–Kassel–Marcus –master equation analysis based on quantum-chemical calculations. The following low- and high-pressure limiting rate coefficients were obtained over the temperature range T?=?300–3000?K: (Formula presented.). with the center broadening factor Fc?=?0.119.
- Bystrov, Nikita,Emelianov, Alexander,Eremin, Alexander,Loukhovitski, Boris,Sharipov, Alexander,Yatsenko, Pavel
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- Dissociation dynamics of fluorinated alkyl iodides at 222 and 236 nm
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I*(2P1/2) quantum yield has been measured for a series of fluorinated alkyl iodides at two different wavelengths in the blue wing of their A-band. The yields are much higher for the fluorinated iodides than their corresponding alkyl iodide analogs at 222 as well as 236 nm. The I* quantum yield at 222 nm is, in general, larger than that at 236 nm which is opposite to what has been found in normal alkyl iodide dissociation in the A-band. This difference in fluorinated iodides has been explained by invoking the participation of the B-band states in the dissociation dynamics.
- Kavita,Das, Puspendu K.
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- Atmospheric Chemistry of HFC-227ca: Spectrokinetic Investigation of the CF3CF2CF2O2 Radical, Its Reactions with NO and NO2, and the Atmospheric Fate of the CF3CF2CF2O Radical
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A pulse radiolysis technique was used to study the UV absorption spectrum of CF3CF2CF2O2 radicals, at 230 nm ? = (3.2 +/- 0.4)E-18 cm2 molecule-1.Rate constants for reactions of CF3CF2CF2O2 radicals with NO and NO2 were k3 > 7E-12 cm3 molecule-1 s-1 and k4 = (7.6 +/- 2.4)E-12 cm3 molecule-1 s-1, respectively.The rate constant for reaction of F atoms with CF3CF2CF2H was determined by using an absolute rate technique to be (3.6 +/- 1.3)E-13 cm3 molecule-1 s-1.The atmospheric fate of CF3CF2CF2O radicals is decomposition via C-C bond scission to give CF3CF2 radicals and CF2O.In one bar of SF6 at 296 K, CF3CF2CF2O radicals decompose with a rate > 1.5E5 s-1.In their turn CF3CF2 radicals are converted into CF3CF2O radicals which also decompose via C-C bond scission.As part of this work a relative rate method was used to measure k(Cl + CF3CF2CF2H) = (3.4 +/- 0.7)E-16 and k(F + CF3CF2CF2H) = (3.2 +/- 0.8)E-13 cm3 molecule-1 s-1.The results are discussed with respect to the atmospheric chemistry of HFC-227ca.
- Giessing, Anders M. B.,Feilberg, Anders,Moegelberg, Trine E.,Sehested, Jens,Bilde, Merete,et al.
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- α-Branched-perfluorodiacyl peroxides: Preparation and characterization
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New perfluorodiacyl peroxides substituted at the α position have been synthesized and characterized. This class of peroxides shows good hydrolytic stability.
- Galimberti, Marco,Barchiesi, Emma,Navarrini, Walter
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p. 587 - 593
(2007/10/03)
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- MEASUREMENT OF RATE CONSTANTS AND EQUILIBRIUM CONSTANTS OF RI R + I AND I + RI I2 + R FOR R = C3F7, iso-C3F7, C6F13, CF3OCF2CF2, OR C3F7OCF2CF2
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The method of isothermal pyrolysis of an iodide RI can produce highly accurate data about the equilibrium constants and rate constants of the reactions RI R + I and I + RI R + I2, if the rate constant for recombination R + R -> R2 is known.Data on the absolute rate constants of the thermal dissociation of the iodides C3F7I, iso-C3F7I, C6F13I, CF3O(CF2)2I and C3F7O(CF2)2I, and also for their reaction with atomic iodine were obtained for the first time using this technique.The dissociation energies ED (R-I) are 212+/-2, 201+/-2, 202+/-2, 213+/-2, and 213+/-2 kJ/mole, respectively.
- Skorobogatov, G. A.,Dymov, B. P.,Tedeev, R. Sh.
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p. 158 - 165
(2007/10/02)
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- Quantum yields of I(2P1/2) for CF3I, C2F5I, i-C3F7I, n-C3F7I, n-C6F13I, and 1,2-C2F4I2 at 308 and 248 nm
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A new method is applied to measure the wavelength-resolved quantum yields of I(2P1/2) for six molecules relevant to the iodine I(2P1/2) atoms and accounts for the strong exciplex emission, also at 1.3 μm, from the I(2P1/2)-iodide molecules.In addition, digital processing is used to correct for noise, quenching, and the detector rise time.These features avoided the shortcomings of previous measurements.The following molecules were investigated: CF3I, C2F5I, i-C3F7I, n-C3F7I, n-C6F13I, and 1,2-C2F4I2.All six iodides present high yields of I(2P1/2) at the pumping wavelength of 308 and 248 nm used.The high I(2P1/2) yields for the molecules n-C6F13I and 1,2-C2F4I2 are reported for the first time.
- Gerck, Edgardo
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p. 311 - 315
(2007/10/02)
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