Ultrafast Dynamics of Electronic excited state in molecules with electric field observables in four-wave mixing*

We measure the femtosecond electric field of the degenerate four-wave mixing (DFWM) signal from both ground-state and UV-excited (240 nm) state molecules. In this setup, three femtosecond pulses of 800 nm interact with both excited and ground-state molecules, with two pulses time-delayed relative to the third by attosecond steps. The electric field of the third-order nonlinear signal (DFWM signal) generated during this process is then measured using the interferometric technique called TADPOLE. Our results demonstrate that the amplitude and phase of the signal can provide valuable insights into the ultrafast electronic dynamics of excited molecules.