Measurements of the absolute concentrations of hydrogen atom and hydroxyl produced in the silyl + oxygen reaction: determination of the product branching ratios

Abstract

Absolute concentrations of H atoms and OH radicals were measured to determine the product branching ratios for the reactions SiH3 + 0 2 -SiH20 + O H (1 b) and SiH3 + 0 2 -SiH202 + H (IC) by using laser-induced fluorescence (LIF) techniques. The intensity of the VUV-LIF signal of H atoms at Lyman CY wavelength was calibrated against the absolute concentration determined by the simultaneous measurement of the Lyman CY resonant absorption. The calibration for the UV-LIF signal intensity of O H radicals has been performed by the simultaneous measurements of the VUV-LIF of H atoms and UV-LIF of O H produced in the O(1D) + H2 -O H + H reaction system: since the reaction of O(lD) + H2 produces equal amounts of H and OH, the absolute concentration of O H could be known from the H-atom concentration derived from the VUV-LIF intensity of H atoms. It was found that vibrationally excited OH in v"=1 was also produced by reaction l b with a ratio of [OH(v"=l)]/[OH(v"=O)] = 0.49 f 0.08. The yields of H and OH in the SiH3 + 0 2 reaction were derived from the measured absolute concentrations of H and OH combined with the absolute concentrations of SiH3 determined by the time-resolved mass spectrometry. The branching ratios of 0.25 and 0.65 for reactions l b and IC, respectively, were obtained on the basis of kinetic simulations for the yields of H and OH.

Heterophase combustion of silane near the first ignition limit

“…A modern laser RFS setup with the multiplication of light frequency to record hydrogen atoms in [12] has a working range of 10 11 < [H] < 2.6·10 12 atom/cm 3 , which is almost three orders of magnitude inferior to the sensitivity threshold and working range of the present work.…”

“…The chain-branching process (CBP) of oxidation of silane (SiH 4 ) was investigated in [3][4][5][6][7][8][9][10][11][12][13][14][15]. Azatyan et al [5][6][7] studied the reactor surface in contact with silane flame in oxygen.…”

“…Azatyan et al [5][6][7] studied the reactor surface in contact with silane flame in oxygen. Intermediate reaction products (H, O, OH, SiH 3 , :SiH 2 , SiO, Si, SiH 2 O 2 , and SiH 2 O) in gas have been examined by modern methods [8,[11][12][13][14]. The final gas-phase products in this reaction are water and molecular hydrogen [8].…”

“…In [6], the conclusions of [1,3] concerning gas-phase chain branching in silane combustion were extended by the conclusion on heterogeneous chain branching. Later, the fast reaction of SiH 3 radicals with molecular oxygen in gas was studied [8,[11][12][13], and it was assumed in [8] to be the main branching reaction for the gas-phase part of the process. In an early study [4], expansion of the ignition peninsula was found in experiments with mixtures richer in silane and it was inferred that SiH 4 molecules participate in the chain branching reaction.…”

Non-Wave Variations in Temperature Caused by Sound in a Chemically Reacting Gas

“…For the branching reactions such as SiH 3 → products, or H → products, the characteristic duration of reaction is of order of 10 −3 s [11].…”