A method for planar measurement of temperature in a compressible flow by means of two-line laser-induced iodine fluorescence is proposed. Temperature is determined from the ratio of the intensities of fluorescence, which are obtained by irradiation of two laser beams of different wavelength. Use of a high-sensitivity vidicon camera permits multiple-point measurements of temperature in the flow field. This method is applied to a supersonic free jet. It is found that the results obtained by P(16)/R(18) (514.720 nm) and P(26)/R(28) (514.942 nm) absorption lines in the transition of B 3IIou+ (υ′ = 43) ← X 1Σg+ (υ″ = 0) can predict temperature below 300 K with an accuracy of ±5 K.
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