Towards Time-Resolved Molecular Orbital Imaging

Understanding the mechanism of a chemical reaction is essential for controlling selectivity and yields of products or designing a novel molecular function, which is one of the ultimate goals of chemistry. Since a chemical reaction can be defined as nuclear dynamics driven by the change in electron motion, time-resolved molecular orbital imaging would open the door not only to gain a deeper insight into molecular dynamics but also to advance and extend frontiers of science and technology. In this chapter, two experimental techniques that aim to visualize the changing molecular orbital pattern during a chemical reaction are described in detail. One is the attempt to tackle the issue in momentum space, and the other is the attempt to do the same based on laser tunneling ionization. It is demonstrated that these two techniques are each applicable to short-lived excited states, thereby both offering opportunities for investigating the driving force behind chemical reaction.