Nonlinear Spectroscopy: Characterizing Fluctuations Andrei Tokmakoff MIT Department of Chemistry 2009
Fluctuations in lineshapes
System-Bath Interactions System: Spectroscopically Bright States Bath: Dark States → Energy Gap Fluctuations In spectroscopy … (Condon Approx.)
Energy Gap Fluctuations Energy Gap Correlation Function Dipole Correlation Function → Absorption lineshape Second Cumulant approx.
A bath of arbitrary form Spectral Density Brownian Oscillator Model
Nonlinear response for fluctuating system Following earlier approach: Cumulant approximation:
Two pulse echo ~1/
Two pulse echo
Lens analogy
Three pulse echoes: Peak shift
2D Lineshapes
Spectral Diffusion and Waiting Time
Time-domain 2D Spectroscopy
Time-Domain: Echo shape
2D IR Relaxation Experiment Probes Spectral Diffusion
Ellipticity
Correlation of Spectral Broadening
Correlation Effects in 2D IR Spectra
Correlated Energy Fluctuations Frequency Auto- and Cross-Correlation Functions: