10097-28-6Relevant academic research and scientific papers
Investigation of the Prototype Silylene Reaction, SiH2 + H 2O (and D2O): Time-Resolved Gas-Phase Kinetic Studies, Isotope Effects, RRKM Calculations, and Quantum Chemical Calculations of the Reaction Energy Surface
Becerra, Rosa,Cannady, J.Pat,Walsh, Robin
, p. 11049 - 11056 (2003)
Time-resolved kinetic studies of the reaction of silylene, SiH 2, with H2O and with D2O have been carried out in the gas phase at 296 and at 339 K, using laser flash photolysis to generate and monitor SiH2. The reaction was studied over the pressure range 10-200 Torr with SF6 as bath gas. The second-order rate constants obtained were pressure dependent, indicating that the reaction is a third-body assisted association process. Rate constants at 339 K were about half those at 296 K. Isotope effects, kH/kD. were small averaging 1.076 ± 0.080, suggesting no involvement of H- (or D-) atom transfer in the rate determining step. RRKM modeling was undertaken based on a transition state appropriate to formation of the expected zwitterionic donor-acceptor complex, H2Si ... OH2. Because the reaction is close to the low pressure (third order) region, it is difficult to be definitive about the activated complex structure. Various structures were tried, both with and without the incorporation of rotational modes, leading to values for the high-pressure limiting (i.e., true second-order) rate constant in the range 9.5 × 10-11 to 5 × 10-10 cm3 molecule-1 s-1. The RRKM modeling and mechanistic interpretation is supported by ab initio quantum calculations carried out at the G2 and G3 levels. The results are compared and contrasted with the previous studies.
Chemistry of semiconductor clusters: Large silicon clusters are much less reactive towards oxygen than the bulk
Jarrold, Martin F.,Ray, Urmi,Creegan, Kathleen M.
, p. 224 - 229 (1990)
The chemical reactions of Sin+ (n = 10-65) with O2 have been investigated using selected ion drift tube techniques.The smaller clusters are etched by O2 to give Sin - 2+ (and two SiO molecules) and the larger clusters chemisorb oxygen forming an SinO2+ adduct.The transition occurs between n = 29 and 36 under the conditions employed.There are large variations in the reactivity of the smaller clusters: Si13+, Si14+, and Si23+ are particularly inert.The variations in reactivity are rapidly damped with increasing cluster size and for clusters with 40-65 atoms the reactivity is nearly independent of size.However, these large clusters are ca. 102 times less reactive towards O2 than most bulk silicon surfaces.Studies of the temperature dependence of the reactions reveal that they proceed through a metastable precursor state which is probably molecular O2 physisorbed to the cluster surface.Variations in the size of the activation barrier for dissociative chemisorption account for the changes in reactivity with cluster size.However, the difference between the cluster and surface reactivities is not due to the size of the activation barrier, but could be accounted for by the presence of only a few reactive sites on the clusters.
Infrared spectra and density functional calculations of the SiCO4 molecule in solid argon
Dong, Jian,Miao, Lei,Zhou, Mingfei
, p. 31 - 36 (2002)
The SiCO4 molecule has been produced by reaction between silicon dioxide and carbon dioxide molecules in solid argon. Silicon dioxide molecules were prepared by reactions of laser-ablated silicon atoms with oxygen in excess argon. When carbon d
Infrared spectrum of matrix isolated ClSiO and ab initio calculations
Junker, Markus,Schnoeckel, Hansgeorg
, p. 3769 - 3772 (1999)
Cl atoms and SiO molecules are trapped in a solid Ar matrix at 16 K. The formation of the as yet unknown ClSiO molecule has been followed via its IR spectrum. The stretching frequencies of the isotopic isomer 35Cl28Si16O are observed at 1160.9 and 509.4 cm-1. Experiments with the 18O isotopic isomers were performed in order to confirm the assignment of the absorptions and to characterize the force field. With the help of quantum chemical calculations (DFT) the optimized ClSiO bond angle is obtained at 125.2°. The computed bond lengths are determined to be 153.6 pm for d(Si-O) and 207.8 pm for d(Si-Cl). The SiCl bond is weak in comparison with that of Cl2SiO (203.4 pm) which is in line with a decrease in the corresponding Si-Cl force constant. The calculation of its thermodynamic data, ΔfH0(298) = -167.2 kJ/mol; ΔfS0(298) = +279.1 J/(mol·K), is of high importance for high temperature gas phase reactions of industrial processes, e.g., the combustion of SiCl4 by O2.
Kinetics of the SiH3 + O2 reaction: A new transition state for SiO production
Murakami,Koshi,Matsui,Kamiya,Umeyama
, p. 17501 - 17506 (1996)
The mechanism of SiO formation in the laser photolysis of SiH4/O2/CCl4 mixtures was investigated using a laser-induced fluorescence method. Measured rates for the SiO production corresponded to the decay rates of SiH3 radical and depended linearly on the O2 concentration. The yield of SiO was estimated on the basis of LIF intensity, and it was found that SiO was one of the major products in the SiH3 + O2 reaction. The bimolecular rate constant for the SiO production was determined to be (1.14 ± 0.18) × 10-11 cm3 molecules-1 s-1. Ab initio molecular orbital calculations were performed for various pathways of the SiH3 + O2 reaction. Geometries were optimized at the MP2(full)/6-31G(d) level of theory, and relative energies and barrier heights were calculated at the G2(MP2) level of theory. Silyl radical and O2 react to form SiH3OO, which irreversibly decomposes to various excited products. A new transition state for the production of cyclic H2SiO2 (siladioxirane) + H from SiH3OO adduct was found. Possible decomposition channels of the vibrationally excited products of the SiH3 + O2 reaction to produce SiO are discussed.
Reaction dynamics of Si (PJ3) + O2 →siO (X 1? +) +O studied by a crossed-beam laser-induced fluorescence technique
Yamashiro, R.,Matsumoto, Y.,Honma, K.
, p. 1 - 6 (2009/02/05)
Oxidation reaction of the ground state Si atom was studied by using a crossed molecular beam technique at 13.0 kJmol of collision energy. The Siatomic beam was generated by laser vaporization and crossed with the ox ygen molecular beam at right angle. Products at the crossing region weredetected by the laser-induced fluorescence (LIF). The LIF of SiO (A &Pi ;1 -X +1) was used to determine the vibrational state distribution of the electronic ground state, SiO (X +1). The determined distribution was inverted with the maximum population at v″ =4, and in good agreement with the recent quasiclassical trajectory calculation on the singlet potential energy surface. The agreement suggested that an abstraction mechanism is dominant at the collision energy studied here. One of the counterproducts, O (PJ3), was also observed by the vacuum ultraviolet LIF and the distribution of the spin-orbit levels were determined. The formation of O (PJ3) was consistent with the significant population of v″=7 and 8 states of SiO, which could be explained by the presence of the triplet product channel with higher exothermicity.
Raman-spectroscopy of oligomeric SiO species isolated in solid methane
Friesen, Markus,Junker, Markus,Zumbusch, Andreas,Schnoeckel, Hansgeorg
, p. 7881 - 7887 (2007/10/03)
From the IR-spectra of matrix isolated SiO species a D2h-structure has been postulated for the dimer and a D3h-structure for the trimer. High quality Raman-spectra - necessary for the complete characterization - were missing so far. Here we report the Raman-spectra especially of the totally symmetric vibrations for Si2O2 and Si3O3 and their 16O/18O isotopomers isolated in solid methane. We also detect the most intense A1-vibration of Si4O4 and can assign it with its 16O/18O isotopic splitting. Ab initio calculations for all oligomers are presented in order to support the assignment of the spectra and to obtain geometric and energetic information about the oligomeric species which have been detected experimentally.
High-Temperature Kinetics of Si Atom Oxidation by NO Based on Si, N, and O Atom Measurements
Mick, H. J.,Matsui, H.,Roth, P.
, p. 6839 - 6842 (2007/10/02)
In the present investigation the well-known high-temperature thermal decomposition of silane was used as Si atom source.Its oxidation by NO was studied behind reflected schock waves in SiH4/NO/Ar systems by applying the atomic resonance absorption spectroscopy (ARAS) technique for detecting Si, N, and O atoms.Initial mixtures of 0.5 - 10 ppm SiH4 and 75 - 300 ppm NO in Ar were used to perform experiments in the temperature range 1660 K SiO + N (R3), k3, was determined by applying the first-order method, which is known to be independent of calibration.The results were summerized by the Arrhenius expression k3 = 3.2 * 1013 exp(-1775 K/T) cm3 mol-1 s-1 (+/- 40percent).To confirm the correctness of reaction R3, N atoms were also measured in the SiH4/NO/Ar system.In that case the formation of N atoms via reaction R3 and the consumption by the reaction with NO, N + NO N2 + O (R4), was observed.By computer simulations all measured N atom concentrations were fitted to the calculated ones by varying the rate coefficient k4.A temperature-independent value of k4 = 2.0 * 1013 cm3 mol-1 s-1 (+/- 50percent) was obtained.Finally O atoms were measured in the SiH4/NO/Ar system.All O atom profiles observed were well fit by computer simulations based on a reaction scheme containing the dissociation of silane, reactions of Si and N with NO, and the well-known O + H2 OH + H reaction.
Structure of (SiO)2: A Comparison between (AlF)2, (SiO)2, and (PN)2. Matrix Infrared Investigation and ab Initio Calculation
Schnoeckel, Hansgeorg,Mehner, Thomas,Plitt, Harald S.,Schunck, Stephan
, p. 4578 - 4582 (2007/10/02)
The structure of dimeric SiO is reexamined by a study of the IR spectra of the matrix-isolated species.Spectra of isotopomers from experiments with 29Si- and 18O-enriched samples are discussed with the help of normal-coordinate analysis.The results are in line with data of the geometrical and electronic structure obtained by ab initio SCF calculations.The dimerization energy calculated by quantum chemical methods agrees well with experimental data, which have been recalculated.With the help of additional ab initio calculations on the isoelectronic species PN and AlF, interesting correlations between their tendency toward dimerization can be obtained.Structural data of SiO are compared with the analogous ones of similar molecules (e.g., BF).
