Effects of Sample Tumbling and Rotation

In most studies of oxide surfaces, the EPR spectra will be powder-Uke in origin. However, in some cases, studies may be performed at the liquid-soUd interface. 

In such circumstances, the resulting spectral profile may produce a composite profile containing both isotropic and anisotropic signals. It is rare that the spectra will be completely averaged, and frequently one may only observe distortions to the anisotropic signal (i.e. a broadening of the lines). It is therefore important to consider such effects in some detail. 

This partial averaging of the signals can be easily explained by reference to the dependence of the linewidths on the value of nij. For an S = 1/2 spin system, the peak-to-peak linewidths ABp.p of the first derivative signal can be expressed as a polynominal in mj. 

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