The overall rate constant and the product branching rate constants have been measured for the first time for the reaction where k2=k2a+k2b. The measurements were made in a flow tube apparatus at T=302±2 °K at a total pressure of 3 Torr. O(3P) was produced by the titration of active nitrogen with NO. H2(v=1) was produced by a heated tungsten filament and its concentration was determined from vuv absorption measurements in the Lyman band system of H2. Absolute concentrations of OH(v=0) and OH(v=1) were deduced from laser induced fluorescence in OH in a calibrated fluorescence system. The rates and uncertainties are k2= (1.0+0.9−0.6) ×10−14 cc/molecule-sec, k2a= (1.0+0.4−0.6) ×10−14 cc/molecule-sec, k2b?4.7×10−15 cc/molecule-sec.
The reported value for k2 represents an increase owing to vibrational excitation in hydrogen by a factor of ?2.6×103 over the fully ground state reaction rate constant. Measurements of the fully ground state reaction rate constant and recent theoretical treatments of the O+H2 reaction are discussed in relation to these results.
Measurements of electron density behind a shock wave in air are presented. Operating conditions are such that shock-wave deceleration, boundary-layer mass loss, and chemical nonequilibrium are important in the determination of the development of the electron density behind the shock wave. A one-dimensional unsteady analysis is described. Calculated electron density is compared with experimental values. Agreement is within a factor of 2. The difference is probably attributable to expansion waves embedded in the test gas.
A review of investigations of microwave breakdown in high-temperature air reveals significant discrepancies between theoretical expectations and experimental observations. Experimental measurements obtained in shock-heated air are presented to confirm the temperature dependence of ionization frequency previously observed. The data are examined with regard to the nonequilibrium thermodynamic state of the gas behind the shock wave. An explanation is offered that attributes the temperature effect to the temperature dependence of the electron-molecule energy-transfer rate, and a method for modifying the conventional theory to take account of this is indicated. The relevance of these results to antenna breakdown on reentry vehicles is discussed.
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