Circular Dichroism of Dimers and Higher Oligomers

Dimers and larger oligomers often exhibit relatively strong CD even when the individual molecules do not [13, 20-25]. To see how this CD arises, let s describe the excited state of an oligomer by a linear combination of the excited states of the individual molecules as in Eqs. (8.17) and (8.19)  

We then can write the oligomer s electric and magnetic transition dipoles as 

Following the procedure we used above in Eqs. (9.5a)-(9.7), we can evaluate the magnetic transition dipoles of the subunits by breaking the position vector for electron / in subunit n into two parts  

Here R is a vector from the origin of the coordinate system to the center of subunit n, and r- is a vector from the center of this subunit to the position of the electron (Fig. 9.6). With this decomposition of mi,a(n) becomes the sum of two terms  

The term m a(n) in this expression is an intrinsic property of subunit n and is independent of where this molecule is located in the oligomer. The term e/lmc) 

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