2D spectroscopy (like 2D-IR) acts like "optical NMR," showing you which parts of a molecule are vibrating near each other. Environment:
By scanning the time delays between these pulses in the lab, you are directly mapping out the shape of
In linear optics (like a standard UV-Vis scan), you can imagine electrons attached to nuclei by simple springs. You pull the spring (hit it with light), and it oscillates at the same frequency. nonlinear optics 2D spectroscopy (like 2D-IR) acts like "optical NMR,"
: You are measuring dephasing (( T_2^* )), not population decay (( T_1 )). Dephasing includes pure dephasing (( T_2^* = 1/T_1 + 1/T_\textpure )). Your ( t_1 ) and ( t_3 ) delays are sensitive to ( T_2^* ), not ( T_1 ).
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of the material is directly proportional to the electric field
If your sample is inhomogeneously broadened (e.g., dyes in a polymer, proteins in water), block the non-rephasing direction. Use the rephasing (echo) direction. Mukamel proves this with time-reversal symmetry; you just need to align your mirrors. nonlinear optics : You are measuring dephasing ((
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