- Experimental and Transition-State Theory Studies of the Gas-Phase Reactions of AlCl with N2O, CO2, and SO2
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The high-temperature fast-flow reactor technique has been used to make kinetic measurements.A weighted fit to the AlCl + N2O data gives k(700-990 K) = 5.6 x 10-11 exp(-7380 K/T) cm3 molecule-1 s-1.A weighted fit to the AlCl + CO2 measurements leads to the expression k(900-1790 K) = 4.4 x 10-23 (T/K) -14 K/T) cm3 molecule-1 s-1. 2? accuracy limits are about +/- 25percent.An upper limit k(800-1100 K) -14 cm3 molecule-1 s-1 has been determined for the AlCl + SO2 reaction.An alternate form of classical transition-state theory is developed to allow predictions on the preexponential part of rate coefficient expressions for metallic species.This model-based transition-state-theory (MTSZ) method used a valence-force molecular model to estimate rotational constants and vibrational frequencies of the transition state and is applicable to reactions with early barriers, typical of many exothermic charge-transfer reactions.The geometrical parameters and force constants that describe the molecular model are derived from properties of the reactants.For the N2O reaction good agreement between MTST and experiment is obtained, based on the assumption of an O atom abstraction reaction leading to OAlCl.No such agreement is found for the CO2 reaction, which indicates adduct formation as the main AlCl consumption channel.For the previously measured AlCl + O2 reaction MTST calculations suggest that abstraction can be some significance above 1500 K; however, adduct formation appears to dominate over most of the 490-1750 K range.
- Futerko, Peter M.,Fontijn, Arthur
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- The molecules AlO2, Al(O2)2, and Al(O 2)3: Experimental and quantum-chemical investigations on the oxidation of aluminum atoms
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(Chemical Equation Presented) On the route to alumina, oxygen-rich oxides such as Al(O2)3 (see picture) are detected spectroscopically during the stepwise oxidation of aluminum atoms and confirmed structurally by quantum-chemical cal
- Stoesser, Gregor,Schnoeckel, Hansgeorg
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- A High-Temperature Fast-Flow-Reactor Kinetics Study of the Reaction AlO + CO2 -> AlO2 + CO. Thermochemical Implications
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The title reaction has been studied in a high-temperature fast-flow reactor (HTFFR) at temperatures from 500 to 1300 K.Laser-induced fluorescence was used to monitor relative . k(T) was determined to be (2.5 +/- 1.3) * 10-14 exp cm3 molecule-1 s-1 (confidence level > 95percent).The reaction probably proceeds via an intermediate complex which preferentially dissociates to the reactants.The negative activation energy implies D(O-AlO) >/= D(O-CO) = 127 kcal mol-1, which is incompatible with the O-AlO dissociation energy obtained for AlO2 from Al2O3 evaporation-mass spectrometry studies.It is argued that the latter AlO2 may have a different structure from that of the present work.
- Rogowski, Donald F.,English, Andrew J.,Fontijn, Arthur
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- Reactions of Pulsed-Laser Evaporated Aluminium Atoms with Oxygen. Infrared Spectra of the Reaction Products in Solid Argon
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Reactions of pulsed-laser evaporated Al atoms with O2 in a condensing argon stream gave cyclic-AlO2 at 496.3 cm-1 as the major product.In addition sharp new absorptions at 1211.2, 1176.3, and 1129.5 cm-1 are identified on the basis of isotopic shifts and multiplets as linear OAlOAlO, AlOAlO, and OAlO, respectively.The identification of linear OAlOAlO and AlOAlO was confirmed by MP2 calculations of isotopic frequencies.The 1129.5 cm-1 band exhibited a sharp mixed oxygen isotopic triplet and isotopic ratio 1.0261 in agreement with that expected for a linear molecule.A sharp 1092.5 cm-1 absorption is identified as OAlOO on the basis of a mixed oxygen isotopic quartet with 16O2/16O18O/18O2 and 16O2/18O2 reagent mixtures.The only AlO2 isomers observed were the cyclic and linear forms found by theory to be potential minima.The observation of isotopic shifts and mixed isotopic multiplets is absolutely essential for the identification of new transient species.
- Andrews, Lester,Burkholder, Thomas R.,Yustein, Jason T.
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p. 10182 - 10189
(2007/10/02)
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- Raman spectra of the products of the Al + O2 reaction in inert matrices. Possible structure of the Al2O3 molecule
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We have obtained the Raman spectra of the molecules produced by the interaction of Al with O2 in argon and in nitrogen matrices.In the spectra for the Ar matrices we observed bands assigned to totally symmetric vibrations of the Al2O and Al(O2)(cycl.) molecules, and of various polymers of composition (AlO)n.In the spectra for the nitrogen matrices a doublet at 1031, 1024 cm-1 assigned to ν1 of the Al2O3 molecule, is additionally observed.By comparing these results with the i.r. spectra of the system we have calculated the force field of the Al2O3 molecule and we have proposed a model of its structure.
- Rozhanskii, I. L.,Serebrennikov, L. V.,Shevel'kov, A. F.
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p. 276 - 277
(2007/10/02)
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