Parallels between multiple population-period transient spectroscopy and multidimensional coherence spectroscopies

Area of Science:

• Chemical Kinetics
• Spectroscopy
• Physical Chemistry

Background:

• Distinguishing homogeneous and heterogeneous kinetics is crucial for understanding reaction mechanisms.
• Existing methods face challenges in deconvoluting complex kinetic behaviors.
• Multiple Population-Period Transient Spectroscopy (MUPPETS) offers a novel approach.

Purpose of the Study:

• To elaborate on the analogy between MUPPETS and coherence-based spectroscopies.
• To develop spectral representations for MUPPETS experiments.
• To precisely define and differentiate homogeneous and heterogeneous kinetics.

Main Methods:

• Utilizing a modified inverse-Laplace transform to convert kinetic decays into "rate spectra."
• Comparing line broadening mechanisms in rate spectra to frequency-domain spectra.
• Developing spectral representations for 2D MUPPETS experiments analogous to 2D coherence spectroscopies.

Main Results:

• Nonexponential decays manifest as linewidths in rate spectra.
• Homogeneous and heterogeneous kinetics are shown to be counterparts of homogeneous and inhomogeneous line broadening.
• A parallel homogeneous-heterogeneous model for kinetics is defined, enabling separation of contributions.

Conclusions:

• MUPPETS provides a framework to precisely define and distinguish homogeneous and heterogeneous kinetics.
• The developed spectral representations offer new tools for kinetic analysis.
• MUPPETS can fully resolve homogeneous and heterogeneous contributions in nonexponential decays.