Structure and Molecular Motion of Peroxy Radicals in Polymer Matrices

3 Structure and Molecular Motion of Peroxy Radicals in Polymer Matrices 

ESR spectra of peroxy radicals show g-anisotroy when the molecular motion is frozen at low temperatures. The spectra can then be calculated on the assumption that the radicals have completely random orientation in three-dimensional space. 

In order to simulate the ESR spectrum of a peroxy radical, one must calculate the resonance magnetic field, Hr(S2) and the intensity of the ESR transition, I(Hr) which is proportional to the number of radicals for a particular arbitrary orientation with respect to the external field, represents the set of direction cosines of the external field, (cosyi, cosy2, cosys) expressed in the principal axis system of the g-tensor. Hr(S2) is represented by the following Eq. (7.24)  

The ESR spectrum, 1(H) can be calculated from the line shape function G as 

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