Fluorescence saturation measurements of 3-pentanone

The saturation characteristics of 3-pentanone fluorescence were investigated in an ambient temperature and pressure cell by imaging the fluorescence produced by a focused quadrupled Nd:YAG laser beam. The onset of fluorescence saturation was observed at laser fluences around 0.06 J/cm², which is only about 1.3% of estimates that assume a two-level model and use measured values of the fluorescence lifetime and absorption cross-section. A spatially resolved model indicated that the saturation fluence changed only 10% when a Gaussian profile was used instead of a top-hat profile. Laser sources with significantly different temporal profiles will have different threshold fluence levels, but the present results suggest that saturation effects should be monitored in planar laser-induced fluorescence imaging experiments using 3-pentanone.