Removal dynamics of nitric oxide (NO) pollutant gas by pulse-discharged plasma technique.

Nonthermal plasma technique has drawn extensive attentions for removal of air pollutants such as NO x and SO2. The NO removal mechanism in pulse discharged plasma is discussed in this paper. Emission spectra diagnosis indicates that the higher the discharge voltage is, the more the NO are removed and transformed into O, N, N2, NO2, and so forth. Plasma electron temperature T(e) is ranged from 6400 K at 2.4 kV discharge voltage to 9500 K at 4.8 kV. After establishing a zero-dimensional chemical reaction kinetic model, the major reaction paths are clarified as the electron collision dissociation of NO into N and O during discharge and followed by single substitution of N on NO to form N2 during and after discharge, compared with the small fraction of NO2 formed by oxidizing NO. The reaction directions can be adjusted by N2 additive, and the optimal N2/NO mixing ratio is 2 : 1. Such a ratio not only compensates the disadvantage of electron competitive consumption by the mixed N2, but also heightens the total NO removal extent through accelerating the NO oxidization process.

[Studies on laser induced dispersive fluorescence spectroscopy of SO2 molecule excited by two-photon].

The processes of excitation and complicated de-excitation of A-symmetric state in the first-excited band of SO2 molecule were studied experimentally with the techniques of two-photon laser induced dispersive fluorescence spectroscopy where a pulsed dye laser (579 nm) was used as excitation sources. The SO2 molecule which were excited from ground state X1A1 to the high vibrational levels of A1 A2 state by absorbing two photons, will realize the repopulation in several vibration-rotational energy levels of A1 A2, B1 B1 and alpha3 B1 states by internal energy conversion and collision relaxation. Because of transitions to the different vibrational levels of ground electronic state X1 A1 from the ground vibrational levels of A1 A2, B1 B1, and alpha3 B1, the fluorescence spectrum envelopes centered at 305 and 425 nm and the regular fluorescence lines centered at 347.2 nm were formed in the fluorescence spectra. In addition, the process of tri-photon excitation X1 A1 --> C1 B2 of SO2 molecule was observed, and the result of the process was the fluorescence spectrum envelope in 200-278 nm and the overlapping fluorescence lines centered at 425 nm. The harmonic frequencies of the symmetry stretch vibration and the bendvibration and the anharmonic constants of stretch vibration mode and the bend vibration mode of related states were calculated from the experimental data.