Rotational and vibrational pattern interpretation for high-resolution coherent 3D spectroscopy.

High-resolution coherent multidimensional spectroscopy provides an alternative to conventional methods for generating rotationally resolved electronic spectra of gas phase molecules. In addition to revealing information such as the relationships among peaks, it can provide clearly recognizable patterns for spectra that otherwise appear patternless due to rotational congestion. Despite this improvement, high-resolution coherent 2D spectroscopy can still exhibit congestion problems; expansion to the second dimension is often not sufficient to prevent overlapping of peaks from different patterns. A new 3D version of the technique that provides improved resolution and selectivity to help address cases with severe congestion was recently demonstrated. The experimental design and interpretation of data for the 3D technique are significantly more complicated than that for the 2D version. The purpose of this paper is to provide important information needed to plan, run, and interpret results from high-resolution coherent 3D spectroscopy experiments.