TEMPERATURE DETERMINATION OF TRANSIENT SPECIES BY DEGENERATE 4-WAVE-MIXING - APPLICATION OF THE INDEPENDENTLY DETERMINED POWER-LAW OF THE TRANSITION DIPOLE-MOMENT AND GEOMETRIC FACTORS

We investigated the dependence of the degenerate four wave mixing (DFW M)signal intensities on the electronic transition dipole moment of iso lated lines in the A (1) Sigma(+)<--X (1) Sigma(+) transition band of NaH. We applied a new method to determine this dependence in transient species without previous knowledge of the sample temperature. By usin g different appropriate pairs of DFWM lines sharing common lower level , the relative population difference is eliminated. We found that this ratio is well described by a power law (mu(1)/mu(2))(x) where mu(i) i s the electronic one-photon transition dipole moment. As a result of s aturation the exponent x depends on the total laser energy deposited i n the medium. The observations are in good agreement with a modified t wo-level model, which includes the effects of polarization of the lase r beams used in the experimental setup by introducing geometric factor s. The exponent of the integrated signal intensities varies between 3 and 8 for high and low laser intensities with a rapid decrease to high intensities. This makes it possible to compare signal intensities at different DFWM laser intensities in order to obtain relative level pop ulations, i.e., temperature, with high sensitivity. (C) 1996 American Institute of Physics.