Visualization of Chemical Reactions by Ultrafast Imaging

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Due to the advent of ultrafast laser technology, real-time studies of molecular dynamics has become possible. This work combines the pump-probe method using femtosecond laser with two-dimensional ion/electron imaging technique to visualize elementary chemical reactions in the gad phase. We employed (1) intense field Coulomb exposition and (2) photoelectron imaging methods. In the former, many of the valence electrons were removed from a molecule to let them explode due to Coulombic repulsion and the scattering distributions of multiply-charged atomic fragments were visualized. Linearity of triatomic molecules in the course of dissociation was discussed in terms of scattering distributions. In the latter technique, NO and pyrazine molecules were excited to the first electronic state, and electron scattering distributions by one and two photon ionization were imaged. Ultrafast intersystem crossing was clearly visualized for the first time.