2ND-HARMONIC-GENERATION STUDIES OF INCLINED THIN-FILMS

The nonlinear surface susceptibility chi(S)(2) is generally referred t o the system of Cartesian coordinates of the sample. However, since ac tual measurements take place with respect to the laboratory system of coordinates, appropriate transformation of chi(S)(2) is necessary to d educe the underlying susceptibility-components. We demonstrate this by analyzing the second-harmonic signal generated by an inclined sample upon rotation around the s-axis of the laboratory system of coordinate s. The sample consists of two Langmuir-Blodgett-type monolayers of rot ational symmetry around the sample normal, the two layers being separa ted by a plane-parallel flat of 1 mm thickness. The occurrence of a '' symmetry-forbidden'' I(ss)2omega-signal is discussed in detail.