Active spectroscopic methods monitoring of active species in atmospheric radio frequency plasma

Summary form only given. Nonthermal and low temperature plasmas are a subject of great interest in different fields of science and applications. One of the attractive features of non-thermal atmospheric pressure plasma is the ability to produce a large amount of reactive species without the need for elevated gas temperature. Since the gas temperature in atmospheric pressure plasma remains relatively low, the plasma does not cause any thermal damage to the sensitive surface it comes in contact with. These properties make this type of plasma attractive for medical applications like electrosurgery, tissue engineering and surface modification of biocompatible materials. Generation of rf-DBD of a size of cm is strongly desirable f or many fields and can find an application in polymers modification and bio-medicine where uniform and fast treatment is required. In the present work rf-DBD plasma of 13.56 MHz generated in between two electrodes with a size of 50×50 mm at pressure range from sub-atmospheric (300 mbar) to atmospheric (1100 mbar) and power of 20-80 W is studied by optical emission spectroscopy (OES) and absorption spectroscopy (AS). The gas temperature and electron density is estimated f rom the OES measurement. AS is used to record the absolute density of Ar* metastable and resonance states by measuring absorption signal of 794.8, 800.8, 811.53, and 750.4 nm corresponding to excited states 1S₃, 1S₄, 1S₅ , and 1S₂ respectively. Atmospheric pressure plasma jets (APPJs) generally characterized by high concentration of radicals and low gas temperatures are suitable for many applications. The increasing interest in the application of APPJs heightened the need for quantification of the main active species generated by APPJs. Laser -induced fluorescence (LIF) and two-photon absorption laser-induced fluorescence(TALIF) spectroscopy are the major techniques that have direct access to the ground state populations. The- imply two or single photons excitation of the studied species from the ground to an excited state which is following by spontaneous emission (fluorescence) of a photon to an intermediate state. In the atmospheric pressure, quantitative detection of species of interest by LIF and TALIF involves complicated interpretation of the experimental results. The present work uses the time-resolved LIF and TALIF spectroscopy to investigate the temporal behavior of laser excited states in the atmospheric pressure RF plasma, sustained in Ar/0.3%H₂O or 0.3%O₂ mixtures, with a special attention devoted to the proper interpretation of the LIF and TALIF results.