Fast LIF Approach to NO Rotational Temperature and Density Measurement: Application to a Gas-Dynamic Expansion

Abstract

An excitation–detection laser-induced fluorescence (LIF) scheme is proposed for the measurement of the NO rotational temperature and density. It is based on the simultaneous excitation of three NO ro-vibronic transitions from only two—one low and one high—J-rotational levels, with the laser set at a suitable fixed wavelength. The procedure does not require the measurement of the excitation spectrum but only of a well-resolved small spectral region of the fluorescence spectrum. The temperature and the density measurements are based on a reference NO LIF spectrum obtained at a known pressure and temperature that is used as a standard. This method is easy and not time consuming. It has been applied to a gas-dynamic expansion.