The self-exchange of dinitrogen behind reflected shock waves

Abstract

The reaction of an equimolar mixture of 28N2 and 30N2 (4% each) diluted by a mixture of Ne (80%) and Kr (12%) was studied over the temperature and density range 4700-5400 K and 2.5-2. X 10"6 mol cm"3, respectively. The reflected shock zone was sampled by a time-of-flight mass spectrometer at 20-µ8 intervals during typical observation periods of 0.5 ms. The product profiles were fit to the equation (1 -2/29) = exp(-fc'tz), where /29 is the mole fraction of 29N2. The time dependence z was determined to be 2.7 and the rate constants were best represented by the expression k = iO"1,24±0•54 exp(-138 ± 10/RT) µß"2•7. The inert gas dependence was assumed to be first order as reported from a previous single-pulse shock tube investigation. The rate constants from the single-pulse study were recalculated using z = 2.7 and were combined with the results herein. The resulting Arrhenius parameters span the extended temperature range 3200-5400 K: log A = 20.66 ± 0.08; E = 140 ± 1 kcal mol'1. The units of A are cm3 mol"1 s"2,7. The nonlinear time dependence for product formation confirms the earlier proposition of a mechanism which consists of a multistep sequence of reactions.

Spatial and temporal emission spectroscopy of a radio-frequency capacitively coupled low pressure oxygen discharge

“…They do not reach the opposite wall, however, since when they gain a critical energy, they collide inelastically at some fixed distance (5-10 mm) away from the wall at which they originated. The field is sufficient to give electrons enough energy to collide inelastically and to produce new lowenergy electrons by means of reaction 8. When the field efast + M -M+ + 2e"["w (8) again reverses and the rf plate becomes positive, the electrons once again accelerate toward the wall; however, since the positive ion mobility is small compared to the electron mobility, the positive ions remain relatively fixed in the discharge compared to the electrons. This excess of positive ions establishes a field which reduces the effectiveness of the rf field and limits the energy gained by the electrons accelerated toward the wall.…”

“…The process of molecular conversion is best explained by a series of steps in which rotational/vibrational energy is accumulated in a critical amount by reactants prior to the exchange step. 8 Both three and four center geometries contribute to molecular conversion.…”