Web Release Date: October 21,
Two-Dimensional Fluorescence (Excitation/Emission) Spectroscopy as a Probe of Complex Chemical Environments
School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia
Received: July 13, 2006
In Final Form: September 14, 2006
Abstract:
We report a new application of fluorescence spectroscopy for the identification and characterization of chemical species in complex environments. Simultaneous collection of a dispersed fluorescence spectrum for every step of the laser wavelength results in a two-dimensional spectrum of emission versus excitation wavelengths. This two-dimensional fluorescence (2DF) spectrum yields quick and intuitive assignments of a multitude of peaks in the separate fluorescence excitation and dispersed fluorescence spectra as belonging to the same species. We demonstrate the technique with the measurement of 2DF spectra of a discharge of dilute benzene into a supersonic free jet. A multitude of rovibronic bands due to the C2 Swan and C3 comet bands are immediately apparent and even unreported bands can be assigned intuituvely. Custom software filters are employed to enhance or reject emission from one or the other carrier to obtain excitation spectra arising from purely one carrier, or even a specific spectral component of a single carrier. The very characteristic 2DF fingerprints of C2 and C3 permit identification of another unidentified species in the discharge that absorbs at 476 nm, coincident with one of the diffuse interstellar bands.
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