Anomalous Lineshapes and Aging Effects in Two-Dimensional Correlation Spectroscopy

TL;DR

This paper investigates how anomalous relaxation and aging effects influence two-dimensional correlation spectroscopy signals, revealing that different models with similar two-point statistics can produce distinct lineshapes, especially under aging conditions.

Contribution

It introduces a detailed analysis of aging effects in 2D correlation spectroscopy using the continuous time random walk model, highlighting differences in spectral lineshapes for models with identical two-point distributions.

Findings

Different models with the same two-point distribution show distinct lineshapes.

Aging random walks cause 2D lineshapes to depend on initial observation time.

Aging effects persist over long times, affecting spectral signatures.

Abstract

Multitime correlation functions provide useful probes for the ensembles of trajectories underlying the stochastic dynamics of complex systems. These can be obtained by measuring their optical response to sequences of ultrashort optical pulse. Using the continuous time random walk model for spectral diffusion, we analyze the signatures of anomalous relaxation in two-dimensional four wave mixing signals. Different models which share the same two point joint probability distribution show markedly different lineshapes and may be distinguished. Aging random walks corresponding to waiting time distributions with diverging first moment show dependence of 2D lineshapes on initial observation time, which persist for long times.