Optimum Conditions for MO Studies

Of paramount importance when investigating MO is the appropriate choice of experimental method and conditions under which the spectra will have the highest SNR and sensitivity to the MO. The latter implies that three principal components of the absorption index can be measured with comparable SNRs. Except for films on metals, for which only the modes perpendicular to the surface can be detected (Section 1.8.2) and the optimum conditions are known (p-polarized radiation 

In the case of uniaxial LB films (tilt angle of 16°) on glass, the angle-of-incidence dependences of the SNR and the refiectivity for the VasCH2 band in IRRAS are shown in Fig. 3.91. One can see that for this system the optimum angle of incidence from the SNR viewpoint is 70°-73° (for the VasCOO bands this angle is 77°). For the AW interface, the highest SNR in IRRAS has been reported at p 30° in both s- and p-polarized IRRAS [589] and at pi 71°-76° in PM-IRRAS [496, 71]. For all transparent substrates, the SNR in the p-polarized spectra is minimal and extremely poor at pi = (ps (Section 2.3.1). 

The DR fitting measurements of MO in ultrathin films on substrates with low refractive indices (quartz) at angles of incidence higher than 70° are optimum from the viewpoints of both maximum MO sensitivity and minimum inherent method error (for tilt angles 40°) [558]. At the same time, a marked increase 

McIntyre, inB. O. Seraphin (Ed.), Optical Properties of Solids New Developments, North-HoUand, Amsterdam, 1976, p. 555. 

Frohlich, Theory of Dielectrics, 2nd ed.. Clarendon Press, Oxford, 1958. 

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