But the textbooks—notably Mukamel’s "Principles of Nonlinear Optical Spectroscopy" —are terrifying. They start with the density matrix, expand into response functions, and by page 50 you are drowning in Feynman diagrams and Liouville space.
When you open Mukamel, you see spaghetti-diagrams with arrows pointing left and right. These are double-sided Feynman diagrams, and they are the source of 90% of the confusion. Stop being afraid. A Feynman diagram is simply a . These are double-sided Feynman diagrams, and they are
Mukamel doesn’t treat molecules as static balls; he treats them as quantum statistical ensembles. Mukamel doesn’t treat molecules as static balls; he
You do not need to derive the response function from the Hubbard-Stratonovich transformation. You do need to know that rephasing = echo = inhomogeneous broadening suppressed, and non-rephasing = homogeneous broadening only. intimidating diagrams—Feynman diagrams
Consider a standard three-pulse photon echo (a (\chi^(3)) experiment):
Sam pulled up a chair and flipped the book open to a page covered in dense, intimidating diagrams—Feynman diagrams, but with more lines and a lot of attitude.