Nonlinear molecular spectroscopy

1. Sum-of-states (SOS) for multilevel system

   Pros: computationally cheap and intuitive

   Note

   In the SOS method, decay is introduced phenomelogically.

2. correlation function approach – Direct computing the many-point correlation functions with the quantum regression theorem

   Valid for open quantum systems where environment effects can be rigirously described with quantum master equations.

   Visulize with double-sided Feynman diagrams instead of the time-loop diagrams.

3. non-perturbative approah – valid for ALL systems provided a quantum dynamics solver is provided.

   Simulating the laser-driven dynamics including explicitly all laser pulses