Non-degenerate coupled-oscillator CD

When eda transitions occur in two non-identical achiral chromophores, as with the degenerate case, a linear motion of charge at a distance (in another chromo-phore) has a circular (magnetic) component locally. Thus if the two transitions couple, an induced CD signal (4) is found. The main differences between the non-degenerate and degenerate cases are that for the non-degenerate case  

The CD induced at into the transition on A by its coupling with an edtm of different energy in C is (4) 

A number of general points about non-degenerate coupled-osdllator CD spectra (Rgure 9) follow from equations 10 and 11. 

It is often the case that a = -v = 90 . When this situation arises, the geometry factor in equation 11 is cosrsinT = /zsin(2T) so the CD is a maximum when ijl and are oriented at 45° to one another. 

If we wish to know the combined eifect of many transitions in C on one transition in A. we simply introduce a sum over c into equation 11. 

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Figure 9 Schematic illustration of non-degenerate coupled-oscillator CD spectra for a = 7 = 90° (a) 0 < 2t < 180° and (b) 180° < 2t < 360° (see Figure 8 for definition of t). (Source Circular dichroism and linear diohroism, A. Rodger and B. Nord n, 1997, by permission of Oxford University Press.)...

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