Abstract
The ultimate understanding of a chemical reaction is knowing how each nucleus in the reactant moves
during product formation. Obtaining this thorough knowledge of the reaction coordinate is still very
challenging for polyatomic molecules, because of the many degrees of freedom of their nuclear motions.
To deepen our understanding, it is important to develop new spectroscopic methods and to try to observe
the nuclear motions and structural evolution of the reacting molecule. In this paper, we review our
recent progress in time-resolved spectroscopy for femtosecond structural study, and discuss the nature,
mechanism and dynamics of ultrafast reactions that have been revealed by these advanced methods
