Excited State Number Densities Research Articles

Dynamics of vibrationally excited ozone formed by three-body recombination. II. Kinetics and mechanism

Spectrally resolved infrared chemiluminescence from vibrationally excited ozone, O3(v), has been used to study the reaction kinetics of O3(v) in discharged O2/Ar mixtures at ∼1 Torr and 80–150 K. Dependences of the excited state number densities on temperature and O2 mole fraction indicate O3(v) is formed primarily by three-body recombination of O with O2 and is destroyed by rapid chemical reaction with O. Several secondary excitation reactions involving vibrationally and electronically excited O2 are also indicated. The data are treated with a detailed steady-state analysis of the discharge kinetics, to extract estimates for rate coefficients of the key elementary reactions. The effective ‘‘quasinascent’’ state distribution in recombination is also inferred; this distribution shows selective recombination into the asymmetric stretching mode, but an apparently statistical (i.e., collisionally scrambled) behavior among the vibrational states within that mode. The results are discussed in terms of the detailed dynamics of three-body recombination.

Measurement of excited state number densities of oxygen and nitrogen in a non-equilibrium plasma

Number densities of several excited states of atomic oxygen and nitrogen have been measured in the decaying non-thermal plasma of a θ-pinch afterglow. The spatial variation of the electron density and temperature as functions of time after initiation of main bank discharge have also been measured to facilitate a comparison of the excited state number densities with model calculations. Measurements of the atomic oxygen excited states indicate that quintet to triplet spin exchange collisions and doubly excited states must be included in the model. The measured populations of the excited atomic nitrogen states agree well with those calculated at high density ( N e ≈ 10 14 cm −3), but disagree badly at lower densities ( N e ≈ 10 12 cm −3). The discrepancies seem to be real since they are larger than expected measurement uncertainty.