Photo-generation and annihilation processes of mid-gap states in quasi-one-dimensional halogen-bridged mixed-valence metal complexes

Photo-generation and annihilation processes of the mid-gap states in quasi-one-dimensional halogen-bridged mixed-valence metal complexes (HMMC's) have been investigated by the excitation spectra measurements of photo-induced absorption (PA) bands and excitation power density dependence measurements of the PA bands. One kind of PA bands are efficiently generated from the CT-excitons. On the other hand, another kind of PA bands are efficiently generated from higher energy excited states. The generation efficiencies of the PA bands are proportional to the square root of the excitation light power density. This indicates that the mid-gap states which cause PA bands are mobile and are annihilated by the collision among them.