Slides for PowerPoint: Nonlinear and Two-Dimensional Spectroscopy Andrei Tokmakoff MIT Department of Chemistry
Complete Slides
Why 2D IR Spectroscopy? IR spectroscopy IR probes vibrations intrinsic to all molecules Each vibration gives different information Structure and dynamics Intrinsic time-scale of ~1 ps 2D IR spectroscopy: A more sensitive probe Characterize vibrational correlations Couplings, orientation, exchange Resolves congested spectra & suppresses inhomogeneous broadening Quantitative structure-based modeling
Fourier transform 2D IR spectroscopy
Ultrafast nonlinear spectroscopy mask
Polarization-selective pump-probe experiment Magic Angle: Vibrational Lifetime Anisotropy: Reorientation
Peak Shift Measurement ta – tb (fs)
2D IR Interferometer time/frequency detection time/time detection
2D IR Spectroscopy in pump-probe geometry
Obtaining an Absorptive 2D IR Spectrum
2D IR spectroscopy t2 > tc t2 = 0 Related to the joint probability Frequency Fluctuations Vibrational Couplings Chemical Exchange
Chemical exchange and spectral diffusion Excite: Initial frequency w1 Wait for period t2 Detect: Final frequency w3 t2 → t2 = 0
2D lineshapes: Loss of frequency correlation Absorptive Phase Ellipticity a b Phase slope
Extra Graphics
2D Lineshapes
Rephasing and Non-rephasing
Rephasing and Non-rephasing
2D IR Spectrum of RDC in Hexane
2D IR Spectrum of RDC in Hexane
Polarization-Selective 2D IR Spectroscopy
Projection Angle from Peak Amplitudes