If your signal decays in 100 fs, you have electronic coherences. If it decays in 10 ps, you have vibrational coherences. If it never decays, you have a photoproduct. Principle 7: Common Mistakes Mukamel Newbies Make (And How to Fix Them) Mistake 1: Trying to calculate the exact response function analytically. Fix: Use the impulsive limit (pulses shorter than any dynamics) and Fourier transform your data. The molecule does the integral for you.
This wiggling polarization acts like a tiny radio antenna. It emits a new light field. If your signal decays in 100 fs, you
| | What it means practically | Mukamel term to ignore | | --- | --- | --- | | Exponential decay of echo vs ( t_1 ) | Homogeneous broadening (fast dephasing) | ( T_2^* ) vs ( T_2 ) confusion | | Nonexponential decay (blip at zero delay) | Inhomogeneous broadening (ensemble disorder) | Spectral diffusion function | | Oscillations in 2D spectrum along ( t_1 ) | Quantum beats between coupled states | Coherent artifact from ( \rho_eg^(1) ) | | Diagonal elongation in 2D spectrum | Strong coupling (exciton delocalization) | Redfield relaxation tensor | | Cross-peak appears only after ( t_2 > 0 ) | Energy transfer | Forster rate ( k_ET ) | Principle 7: Common Mistakes Mukamel Newbies Make (And
A diagram has two vertical lines (left = ket, right = bra). Time goes up. Arrows point toward the molecule (absorption) or away from it (emission). This wiggling polarization acts like a tiny radio antenna
If your signal is weak, use a boxcar geometry (beams at three corners of a square). The signal goes out the fourth corner. No fancy optics required.
Ignoring the rotating wave approximation (RWA). Fix: The RWA means you drop terms that oscillate at optical frequencies (they average to zero). Without RWA, you will cry. With RWA, you get simple exponentials.