Laser-Induced Fluorescence of Hydroxyl (OH) Radical in Cold Atmospheric Discharges

The application of laser-induced fluorescence (LIF) to measurement of absolute concentration of hydroxyl radicals in cold atmospheric discharges is described. Though only the case of OH is presented, the method can be directly applied to other molecules as well. Starting from the rate equations for the LIF process, the main formulas for two- and multi-level excitation scheme are derived. It is also shown how to use partially saturated LIF in practice, enhancing the signal-to-noise ratio. Practical tips for automating the data evaluation are given, allowing processing large data sets, particularly suitable for planar measurements. Gas temperature estimation from fluorescence on different rotational absorption lines is shown as an attractive method for obtaining temperature maps with high spatial resolution. The important aspects of calibration are discussed, particularly the overlap of the laser line with the selected absorption line and the measurement of the Rayleigh scattering for sensitivity calibration, together with the common sources of errors. The application of OH(A, v′ = 0 ← X, v″ = 0) excitation scheme to the effluent of atmospheric pressure plasma jet ignited in argon and of OH(A, v′ = 1 ← X, v″ = 0) to the plasma of coplanar surface barrier discharge in air and in water vapor is shown

USING DIFFUSE COPLANAR SURFACE BARRIER DISCHARGE FOR IMPROVEMENT OF FELTING PROPERTIES OF ANIMAL FIBRES

The Diffuse Coplanar Surface Barrier Discharge (DCSBD) has shown its great potential for applications in textile industry recently1. A rather interesting synthesis of the latest technologies and a very traditional industry is currently being developed in cooperation of our physics department and TONAK - a company with more than 200 years tradition in the hat making from natural felt. This is also covered by international patent WO2011044859: An Apparatus and Method for Improving Felting Properties of Animal Fibres by plasma Treatment

Dependence of laser-induced fluorescence on exciting-laser power: partial saturation and laser – plasma interaction

In recent publications on laser-induced fluorescence (LIF), the measurements are usually constricted to the region of weak exciting-laser power – the so called linear LIF. In this work, a practical formula describing the dependence of partially saturated fluorescence on the exciting-laser power is derived, together with practical implementation suggestions and comments on its limitations. In the conclusion, the practical formula

Photofragmentation laser-induced fluorescence of ozone : an in situ tool for precise mapping of ozone concentration in non-thermal plasmas

The absolute spatially resolved concentration of ozone has been determined in the near afterglow of a novel type of atmospheric multi-hollow barrier discharge using photofragmentation laser-induced fluorescence. The method consists of two steps: (i) photodissociation of O-3 to O(P-3) and O-2(X-3 Sigma(-)(g)) with considerable vibrational excitation; (ii) predissociation laser-induced fluorescence of the molecular fragment via the O-2 (B-3 Sigma(-)(u), v' = 0 <- X-3 Sigma(-)(g), v '' = 6) transition. Both processes happen during the same laser pulse, requiring the same excitation wavelength (approximate to 248 nm). The fluorescence signal has been calibrated by infrared absorption. The method allows in situ observation before the afterglow chemistry significantly affects the O-3 concentration, and is capable of revealing inhomogeneous ozone distributions in the reactor. (C) 2019 The Japan Society of Applied Physic