Optical processes in conjugated polymers

There are many excellent accounts of both the theory of optical processes in general (Ziman 1972 Butcher and Cotter 1990 Mukamel 1995 and Loudon 2000), and optical processes in organic (Pope and Swenberg 1999) and inorganic materials (Henderson and Imbusch 1989), in particular. It is the purpose of this chapter to describe some of the important linear and nonlinear optical processes that enable us to establish a connection between the theories of electronic states described in this book and their experimental consequences. 

Linear optical processes give important information about the energies of the dipole allowed states. However, dark states - namely those with no dipole moment to the ground state - are inaccessible. Nonlinear optical processes, on the other hand, involve transitions between two or more states, so these access the dipole-forbidden states. In this chapter we explain how third order nonlinear process can be used to identify these forbidden states. 

Before discussing the nonlinear effects we first establish our notation by discussing linear optical properties. 

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How does the type and character of the electronic states determine the electronic and optical processes in conjugated polymers For example,... 

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