The trick is to initiate the reaction with one laser pulse and use another laser pulse, delayed with respect to the first by bouncing it off a movable mirror, to follow what happens. Since light travels 0.3 mm per picosecond, precise control of the mirror position allows the time of the reaction to be determined. Professor Ghiggino says that in photosynthesis, most of the chlorophyll in the plant's leaves acts as a sort of antenna. Chlorophyll is energised by photons of sunlight. It transfers this energy to the photosynthetic reaction centre then drops back to its ground state, ready to be energised again.
Plants are extremely efficient at converting light energy into the initial reaction products.
We want to know how chlorophyll gathers the light and converts it into an electrochemical potential in less than 200 picoseconds. Such research will help chemists design synthetic compounds to perform similar reactions. We are trying to design novel, supra-molecular structures that combine antennas with reaction centres. We have already discovered that the backbone structure that connects the antenna and the reaction centre is very important in light-energised chemistry. The backbone doesn't just serve to connect the active components together physically, it can act as a wire that enhances the efficiency of the energy and electron-transfer reactions.