“…Jones et al found a large amount of continuum AlOH emission by visible wavelength emission spectra recorded using a spectrometer coupled to a streak camera[28]. Our calculations are in good agreement with the possible emitter formation mechanisms speculated by Oblath and Gole[27] according to the observed experimental results for the Al-H 2 O system. However, the AlOH is not the final product, and the reaction of AlOH with H proceeds via the O−H bond cleavage transition state TS4 and produce products AlO and H 2 .…”
supporting
confidence: 88%
“…It can be seen that AlO and H 2 are the final products in the reaction of Al with H 2 O. The product of AlO has been observed elsewhere [5,[27][28][29]. In 1993, McCleant et al studied the reaction of Al ( 2 P 0 ) with H 2 O over an extended temperature range [30].…”
A theoretical study on the reaction of aluminum with water in the gas phase was performed using the hybrid density functional B3LYP and QCISD(T) methods with the 6-311+G(d,p) and the 6-311++G(d,p) basis sets. The results show that there are three possible reaction pathways that involve four isomers, seven transition structures, and two possible products for the reaction of aluminum with water. The two most favorable reaction pathways were found, whose intermediates and products agreed quite well with experimental results. The enthalpy and Gibbs free energy change of the reaction between Al and H 2 O at 298 and 2000 K were calculated. Some results are also in good agreement with the previous calculations or experimental results.
“…Jones et al found a large amount of continuum AlOH emission by visible wavelength emission spectra recorded using a spectrometer coupled to a streak camera[28]. Our calculations are in good agreement with the possible emitter formation mechanisms speculated by Oblath and Gole[27] according to the observed experimental results for the Al-H 2 O system. However, the AlOH is not the final product, and the reaction of AlOH with H proceeds via the O−H bond cleavage transition state TS4 and produce products AlO and H 2 .…”
supporting
confidence: 88%
“…It can be seen that AlO and H 2 are the final products in the reaction of Al with H 2 O. The product of AlO has been observed elsewhere [5,[27][28][29]. In 1993, McCleant et al studied the reaction of Al ( 2 P 0 ) with H 2 O over an extended temperature range [30].…”
A theoretical study on the reaction of aluminum with water in the gas phase was performed using the hybrid density functional B3LYP and QCISD(T) methods with the 6-311+G(d,p) and the 6-311++G(d,p) basis sets. The results show that there are three possible reaction pathways that involve four isomers, seven transition structures, and two possible products for the reaction of aluminum with water. The two most favorable reaction pathways were found, whose intermediates and products agreed quite well with experimental results. The enthalpy and Gibbs free energy change of the reaction between Al and H 2 O at 298 and 2000 K were calculated. Some results are also in good agreement with the previous calculations or experimental results.
“…A chemiluminescence phenomenon was observed for high concentrations of O 2 . This chemiluminescence is known to come from the production of electronically excited AlO molecules and therefore constrained the usable reactant flow densities to low values (see Table ). 1 LIF spectra of the 2 S 1/2 − 2 P 1/2 and 2 S 1/2 − 2 P 3/2 transitions of aluminum recorded in the CRESU apparatus at two different temperatures: (1a) 141 and (1b) 52 K. In both cases, the delay times between the photolysis and probe laser pulses were made sufficiently long (50 μs) to allow total spin−orbit relaxation. 2 First-order decay of the LIF signal from Al( 2 P 1/2 ) in the presence of 1.5 × 10 13 molecules cm -3 O 2 at 52 K in Ar, fitted to a single-exponential decay, with residual shown above.…”
The first study of the kinetics of Al atoms with O2 at
low and ultralow temperatures is reported. Rate
constants
have been measured from 295 to 23 K using the pulsed laser
photolysis−laser-induced fluorescence (PLP-LIF) technique in a CRESU (Cinétique de Réaction en
Ecoulement Supersonique Uniforme) apparatus.
Rate constants were found to increase monotonically with
decreasing temperature: k(T) = (1.75 ±
0.10) ×
10-10(T/298)-0.25±0.02
exp[(7.3 ± 3.0)/T] cm3
s-1. The rate constant for the reaction
Al with O2 has also been
calculated as a function of temperature using a theoretical approach
based on the adiabatic capture centrifugal
sudden approximation (ACCSA) method. These calculations were found
to be in good agreement with
experimental results and were able to explain the observed temperature
dependence by the open-shell nature
of the reactants. Possible astrophysical implications are also
discussed concerning the chemistry of aluminum
atoms in the interstellar medium.
“…Al atoms have been found to react with individual water molecules [1][2][3][4][5][6][7][8][9][10] and also in conditions of microhydration. [11][12][13] Relay (Grotthuss-type) mechanisms and tunneling play a role in those reactions, which are of technological and astrophysical importance; Al oxide and hydroxide have recently been detected in the space.…”
The Alm((-))·(H2O)n systems are known to undergo water splitting processes in the gas phase giving HkAlm(OH)k((-))·(H2O)n-k systems, which can generate H2. The migration of H atoms from one Al atom to another on the cluster's surface is of critical importance to the mechanism of the complete H2 production process. We have applied a combination of Molecular Dynamics and Rice-Ramsperger-Kassel-Marcus theory including tunneling effects to study the gas-phase evolution of HAl17(OH)((-)), which can be considered a model system. First, we have performed an extensive search for local minima and the connecting saddle points using a density functional theory method. It is found that in the water-splitting process Al17((-))·(H2O) → HAl17(OH)((-)), the H atom which bonds to the Al cluster losses rather quickly its excess energy, which is easily "absorbed" by the cluster because of its flexibility. This fact ultimately determines that long-range hydrogen migration is not a very fast process and that, probably, tunneling only plays a secondary role in the migration dynamics, at least for moderate energies. Reduction of the total energy results in the process being very much slowed down. The consequences on the possible mechanisms of H2 generation from the interaction of Al clusters and water molecules are discussed.
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