Detection of low concentrations of I2 vapor by laser excitation of its fluorescence

The temperature dependence of the concentration of the I₂ vapor was determined by the laser excitation of its fluorescence. The sources of excitation of the I₂ molecules were an argon laser and a cw dye laser. The minimum amount of the I₂ vapor which could be recorded by this methid was 2×10⁶ molecules, corresponding to a concentration of 5×10⁸ molecules/cm³. The minimum detectable number of molecules occupying one vibrational-rotational level was 2.4×10⁴.