C. W. von Rosenberg

Vibrational excitation of ozone formed by recombination

A new facility coupling flash photolysis and time resolved ir detection and uv absorption diagnostics is described. Its application to studying the reaction O+O2+M→ lim (1) O3†+M followed by O3†+M→ lim (2)O3+M with M=O2 or N2 and where O3† denotes vibrationally excited ozone is described. Our results give k1=3×10−34 cm6 sec−1, k2=2×10−14 cm3 sec−1, φ(ν1)+φ(ν3)=1.6, and φ(ν2)=3.7, where φ(νi) is the average number of quanta of energy νi, resulting in mode νi from each recombination (ν1,2,3=1103, 701, 1042 cm−1). This partitioning of the product energy accounts for 50% of the 25 kcal exothermicity of the recombination. These results are peculiar to the model used for interpretation, which is discussed in some detail in the text.

Flash photolysis study of the gas phase recombination of hydroxyl radicals

Rate constants are reported for the reactions OH+OH → H2O+O (where k1 is the rate constant) and OH+OH+N2 → H2O2+N2 (where k5 is the rate constant) measured in a room temperature flash photolysis experiment. Hydroxyl radicals were produced by the photodecomposition of water vapor, and time resolved absorption spectroscopy was utilized to determine the absolute OH concentration. Specific rate constants obtained are k1=2.1±0.2×10−12 cm3/sec and k5=2.5±0.3×10−31 cm6/sec.

Vibrational Relaxation of CO in Nonequilibrium Nozzle Flow, and the Effect of Hydrogen Atoms on CO Relaxation

The vibrational relaxation of carbon monoxide was studied under conditions of rapid nonequilibrium expansion by using a shock tunnel to generate a nozzle flow with stagnation temperatures and pressures of 2000–4500°K and 5–15 atm., respectively. The vibrational temperature of the CO in the supersonic region of the nozzle was obtained from measurements of the first overtone emission at 2.3 μ by using a calibrated infrared detection system. From these data it was determined that the relaxation time of the CO inferred from the expansion experiment is, at most, 5 times smaller than the relaxation time measured behind incident shock waves. This factor of 5 is in sharp disagreement with previously published measurements in CO and N2, which quote factors from 70 to 1000, implying anomalously fast de‐excitation of vibration in expanding flows, but is in agreement with other subsequently obtained measurements. Impurities were found to be more important in this type of experiment than in measurements of relaxation ...

Shock Tube Vibrational Relaxation Measurements: N2 Relaxation by H2O and the CO–N2 V–V Rate

Shock tube measurements of the rates of vibrational relaxation of N2 by H2O and the vibrational exchange between N2 and CO are described. Simultaneous measurements of H2O v2 ν2 band and CO fundamental band ir emission were performed in mixtures of 1%–10% CO+∼1% H2O+N2. Measurement of H2O emission by a calibrated optical system allowed an accurate determination of the concentration of H2O for each run. The CO emission had two, almost decoupled, regions of behavior which allowed determination of two relaxation times: Pτ NCe≈ 1.6 atm· μsec (V–V exchange relaxation time between N2 and CO) and Pτ NH≈ 1.5 atm· μsec (T–V relaxation of N2 by H2O), both for 960 〈T〈2200°K.

Vibrational Relaxation of CO by Fe-Atoms.

Abstract : Shock tube investigations on Fe(CO)5 + Ar mixtures are described. Behind incident shocks we observe immediate decomposition of the iron pentacarbonyl to yield Fe and vibrationally cold CO; the CO is then very efficiently relaxed by the Fe-atoms. The results are interpreted to yield a relaxation time for CO infinitely dilute in Fe at 1 atm of P(tau)(CO, Fe) of about 0.06 atm micro sec for T = 1400-2900K. This is believed to be the first measurement of vibrational relaxation by metal atoms. (Author)

Absolute H2Ov2-band intensity obtained from reacting H2 + O2 mixtures behind shock waves

Abstract Water vapor emission between 4.7 and 10 μ from 1300 to 3600°K has been measured using a shock tube to heat the gas and an optical system calibrated by a black body to measure the radiation. The optically thin data are interpreted in terms of v2-band emission with some contribution, at the higher temperatures, from the pure rotational band. Calculable concentrations of H2O were made behind incident shocks from the reactions of H2 and O2 highly diluted in argon. There is excellent agreement between data taken at the equilibrium and “partial equilibrium” states, thereby providing additional justification for the existence of the partial equilibrium state and Schotts method for calculating it. An integrated band intensity of 338 (+17 per cent - 7 per cent) ama-1 cm-2 at 2000°K is deduced, in good agreement with earlier workers using different techniques. Above 2500°K the measured radiation is less than we calculate for our bandpass, assuming contributions from both the v2 and the rotational bands of H2O; possible reasons for this discrepancy are discussed.

Shock tube studies on Fe(CO)5 + O2: 11 μ FeO emission and kinetics

Abstract Shock-tube experiments to measure the gas phase FeO fundamental vibration-rotation radiative band intensity at 11.5 μ have been performed. In measurements behind incident shocks, equilibrium amounts of FeO formed quickly, and CO2 formation occured more quickly in the presence of Fe and FeO than can be understood on the basis of previous studies of CO + O2 induction times. Measurements with a calibrated optical system at 10.4–16.3 μ wavelength yielded an integrated band intensity for FeO of 450 ama−1 cm−2 ± 32% (2σ limits). A bound for the rate of the reaction Fe + O2→FeO + Ok ⩾ 5 x 10−12 cm3 molecule−1 sec−1 for T = 2400°K is given and a possible mechanism relating FeO to the rapid CO2 formation is discussed.

Atomic line radiation in the infrared

Abstract The present paper considers atomic infrared line emission from states of high angular momentum, which should be significally populated in a high-temperature, equilibrium (LTE) gas. Such states are shown to give rise to a “universal” series of strong lines, the first member of which is at ∼4μ, and corresponds to the puzzling 4 μ-feature by Taylor and Caledonia.Several of the higher members of the predicated series are found in cesium spectra taken in our laboratory.

Energy partitioning in the products of elementary reactions involving OH-radicals*

An experimental program is described in which we looked for vibrational excitation in the products of the reactions (1) OH+H 2 →H 2 O † +H, (2) OH+CO→CO 2 † +H, and (3) OH+OH→H 2 O † +O. No infrared emission was observed in any of the potentially radiating fundamental vibrational modes or strong combination bands of CO 2 or H 2 O by our calibrated detection system, thus enabling upper bounds to be placed on the amount of vibrational excitation occurring in these products. Our results, expressed as a bound on the percent of the exothermicity which could have been deposited in the vibrational states of interest, are as follows: Reaction (1)−H 2 O (2.7μ)≤11%, H 2 O (6.3μ)≤18%; Reaction (2)−CO 2 (2.7 μ) ≤3%, CO 2 (4.3μ)≤0.6%; Reaction (3)−H 2 O (2.7μ)≤2%.