Molecular number flux detection using oxygen sensitive luminophore

Experimental analyses of thermofluid phenomena with a high Knudsen number, related to low-density gas flows or nanotechnologies, need the measurement techniques based on atoms or molecules, such as emission and absorption of photons. Because the principle of the pressure sensitive paint (PSP) technique is based on oxygen quenching of luminescence, the technique has the capability to be applied to high Knudsen number flows such as microflows and low-density gas flows. In this study, to inspect the feasibility of PSP for measurement of pressure on a solid surface in high Knudsen number flows, fundamental properties of three types of PSP [palladium tetrakis (pentafluorophenyl) porphyrin, palladium octaethylporphyrin (PdOEP), and platinum tetrakis (pentafluorophenyl) porphyrin bound by poly[ 1-(trimethylsilyl)-1-propyne] (poly(TMSP))] are examined especially in the range of pressure below 130 Pa (about 1 Torr). As an application of PSP to high Knudsen number flows, we measure the pressure distribution on a jet-impinging solid surface using PdOEP/ poly(TMSP) with very high sensitivity. Moreover, the "pressure" distribution obtained by the PSP is compared with the distribution of the molecular number flux onto the solid surface to investigate the feasibility of number flux measurement by PSP.