  Time-frequency (TF) analysis is a powerful tool for exploring ultrafast
dynamics in atoms and molecules. While some TF methods have demonstrated their
usefulness and potential in several of quantum systems, a systematic comparison
among these methods is still lacking. To this end, we compare a series of
classical and contemporary TF methods by taking hydrogen atom in a strong laser
field as a benchmark. In addition, several TF methods such as Cohen class
distribution other than the Wigner-Ville distribution, reassignment methods,
and the empirical mode decomposition method are first introduced to exploration
of ultrafast dynamics. Among these TF methods, the synchrosqueezing transform
successfully illustrates the physical mechanisms in the multiphoton ionization
regime and in the tunneling ionization regime. Furthermore, an empirical
procedure to analyze an unknown complicated quantum system is provided,
indicating the versatility of TF analysis as a new viable venue for exploring
quantum dynamics.
