Nanosecond Two-Dimensional Resonance Raman Correlation Spectroscopy of Benzil Radical Anion

Nanosecond two-dimensional resonance Raman spectroscopy was used to investigate the photochemistry of the production and decay of the radical anion of benzil in various solvents. A newly developed correlation formalism was applied to a set of time-resolved resonance Raman spectra of the benzil radical anion to generate two-dimensional Raman spectra. Unlike the 2D correlation method previously developed for IR spectroscopy, which was based on signals induced by a sinusoidally varying external perturbation, the new correlation formalism is generally applicable to the studies of any transient spectroscopic signals having an arbitrary waveform. This makes it ideally suited for the analysis of time-resolved spectroscopic signals following photoexcitation. 2D Raman spectra effectively accentuate certain useful information which is sometimes obscured in the original time-resolved spectra. Spectral intensity changes and peak shifts arising from the photochemical reaction processes were clearly observed by the synchronous and asynchronous correlation.