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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 - PowerPoint PPT Presentation
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Slides for PowerPoint:
Nonlinear and Two-Dimensional Spectroscopy
Andrei TokmakoffMIT 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
1T
|| ||r t S S S 2S
Peak Shift Measurement
ta – tb (fs)
2D IR Interferometer
time/frequencydetection
time/timedetection
2D IR Spectroscopy in pump-probe geometry
Obtaining an Absorptive 2D IR Spectrum
2D IR spectroscopy
Frequency Fluctuations Vibrational Couplings Chemical Exchange
• Related to the joint probability
3,final 2 1,initialP , ;
2 = 0 2 > c
• Excite: Initial frequency 1
• Wait for period 2
• Detect: Final frequency 3
Chemical exchange and spectral diffusion
2 = 0
2 →
AbsorptiveCS
2D lineshapes: Loss of frequency correlation
Phase
a
b
Phase slope
Ellipticity
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