Local time-averaged and instantaneous temperature measurements by relief flow tagging

In this paper we demonstrate the feasibility of using the diffusion rate of vihrationally excited oxygen molecules to measure local air temperature. A Uiin line is written by vihrationally exciting oxygen inolccules using the RELIEF techniquc. The rate at which the diameter of the line increases is then meawred, and the temperature is determined by knowing the temperaturc dependence of the diffusion rate. A simultaneous measurement of pressure or density is i-equired, and this can b e obtained from a standard pressurc tap or from Rayleigh scattering. d