VELOCITY-MEASUREMENT OF FREE JETS USING NUCLEAR HYPERFINE-STRUCTURE OF I-2

Axial velocity distribution in an It-seeded Ar free jet is investigate d by the laser-induced fluorescence (LIF) technique using a ring dye l aser with 500 kHz line width. Since the translational temperature in t he flow region is low, the hyperfine structure due to the nuclear spin of It molecules is observed in the spectrum of It B-X bands. The spec trum shape is explained by the quantum mechanical theory and the simul ated spectra coincide with our measurements. First, the possibility of the translational temperature measurement based on the hyperfine spec trum shape is discussed. Then, axial velocity measurement is performed and the results are found to be in good agreement with those of Ashke nas & Sherman. The applicability and the velocity resolution limit of our measurement technique are also discussed.