title: Characterization of spectral diffusion from two-dimensional line shapes.
abstract: The analysis of line shapes in two-dimensional optical and infrared spectroscopies is a powerful approach to characterizing the dynamics of molecules in the condensed phase. Changes in line shape from diagonally elongated to symmetric as a function of waiting time arise from evolution of the transition frequency. We describe a number of quantitative measures of frequency fluctuations and spectral diffusion through the analysis of two-dimensional (2D) line shapes. These metrics are identical to the system's frequency correlation function and independent of population relaxation in the limit of a short time approximation for the 2D response. We also test the broader applicability of these expressions for analyzing three-level vibrational systems and experiments with finite pulses.
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Sean T
authors.initials: ST
authors.lastname: Roberts
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Loparo
authors.forename: Andrei
authors.initials: A
authors.lastname: Tokmakoff