Fluorescence enhancement detected IR (FEDIR) spectroscopy: a new background free IR spectroscopic technique for highly fluorescent molecules

A new background free IR spectroscopic technique, termed as fluorescence enhancement detected IR (FEDIR) spectroscopy for recording vibrational spectra in the supersonic jets, is presented. An application to the N–H and the C–H stretching vibrations of aniline is demonstrated. High fluorescence quantum yield of the higher vibronic levels in the S1 state is prerequisite for this spectroscopic technique. A direct comparison of S/N ratio between the present technique and an earlier technique is also presented.