Mukamel doesn’t treat molecules as static balls; he treats them as quantum statistical ensembles.
Don't memorize the integral equations. Memorize the physical intuition: Mukamel doesn’t treat molecules as static balls; he
He is solving for all possible directions, but in 90% of experiments, you only care about the rephasing (echo) direction. Ignore the rest until you are a pro. but in 90% of experiments