Fast LIF approach to NO rotational temperature and density measurement: Application to a gas-dynamic expansion

An excitation-detection laser-induced fluorescence (LIF) scheme is proposed for the measurement of the NO rotational temperature and density. It is ba sed 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 regio n of the fluorescence spectrum. The temperature and the density measurement s 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 c onsuming. It has been applied to a gas-dynamic expansion.