Nonparametric High-Resolution Coherent 3D Spectroscopy as a Simple and Rapid Method for Obtaining Excited-State Rotational Constants

A new method for generating high-resolution coherent 3D (HRC3D) spectra has been developed that is based on the nonparametric four-wave mixing process MENS (multiply enhanced nonparametric spectroscopy). The resulting spectra have rotational patterns that are different from those produced previously using the parametric four-wave mixing process CARS. A change in the rotational pattern facilitates a new approach to scanning where orthogonal 2D slices in 3D space are combined to make a 3D rotational pattern. This 3D rotational pattern may then be used to calculate rotational constants for levels in the excited electronic state and upper regions of the ground electronic state. Unlike previous forms of HRC3D spectroscopy, this new approach provides a stand-alone rapid and simple tool for the rotational analysis of electronic spectra without the need for obtaining peak positions or molecular constants from other (1D or 2D) forms of spectroscopy.