The second-order nonlinear optical susceptibilities x values greater than 10~6 electrostatic units, although two of the three did not absorb light significantly at the second-harmonic wavelength.

der scharffe Sebel ist mein Acker... U n i v e r s i t ä t P o t s d a mMathematisch-Naturwissenschaftliche Fakultät

Ultrathin ordered organic films with a thickness of a few nanometers to about a tenth of a micrometer show considerable technological potential as a novel class of materials. Of particular interest are their tailor-made electrical and optical properties which are related to their anisotropic molecular structure which itself can be controlled on a molecular scale. A critical review is given of the different aspects of the potential technological applications of ultrathin organic films. Some underlying chemical concepts and the basic problems to be solved in synthesis and preparation prior to application are discussed.

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Communication: Orientation of chromophores by using the Langmuir‐Blodgett film‐prepration procedure, to a degree practically impossible to achieve by poling in polymer matrices in an electric field, has held to materials exhibiting the highest values of the second order susceptibility (χ(2)) yet known. The effect of different functional groups in both phenylhydrazone and stryrylpyridinium compounds on both molecular nonlinearity and order in the films the factors which most strongly influence (χ(2)) has been investigated and a thioether substituent is found to increas (χ(2)) significantly.