• Sep 9, 2025 Principles Of Nonlinear Optical Spectroscopy Shaul Mukamel es: \[ H(t) = H_0 - \hat{\mu} \cdot \mathbf{E}(t) \] where \( \hat{\mu} \) is the dipole operator of the system. The interaction term induces a time-dependent evolution of the system’s density matrix \( \rho(t) \). The central quantity in nonlinear sp By Mr. Ben O'Hara