Dr. Hubert R. Motschmann Profile

Dr. Hubert R. Motschmann

at MPIKG

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Publications (3)

Proceedings Article | 4 December 2003 Paper

New insights in static and dynamic properties of Gibbs monolayer

Valentina Fazio, Jonas Ortegren, P. Koelsch, A. Andersen, Dieter Wantke, Helmuth Mohwald, Hubert Motschmann

Proceedings Volume 5223, (2003) https://doi.org/10.1117/12.509502

KEYWORDS: Molecules, Second-harmonic generation, Interfaces, Infrared radiation, Adsorption, Harmonic generation, Signal detection, Polarization, Capillaries, Infrared spectroscopy

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In this paper we discuss selected equilibrium and dynamic properties of adsorption layers of soluble surfactants. The surface state has been investigated by nonlinear optical techniques based on second order χ⁽²⁾ effects which exhibit a high surface specificity and suppress bulk contributions. The surface tension isotherm σ(c )of the homologous series of n -alkyldimethylphosphine (n =8 −12) can be described by Frumki ’s equation of state which yields the surface interaction parameter, surface coverage and the corresponding area per molecule A . The comparison of the surface tension σ at a given area per molecule A reveals a strong alternation within the homologous series. Odd C_2n±1 layers show a lower surface tension than the adjacent even members C_2n of the homologous series. This effect is also present at low surface coverage (A =1.4nm²)and cannot be attributed to a differences in the chain-packing within a crystalline state. Infrared-Visible Sum-Frequency Generation Spectroscopy (SFGS)has been used to monitor the orientation and chain order within the aliphatic tail. SFGS spectra have been recorded for different chain lengths and at different areas per molecule. The analysis of the spectra yields an order parameter G which is proportional to the number of gauche defects within the aliphatic tail. The odd-even effect in the surface tension turned out to be accompanied by an odd-even effect in the order parameter G. The data suggest that an ordered structure has a bigger impact on the surface tension than an unordered structure. The odd-even effect is also observed in the orientation of the terminating methyl group as retrieved by polarization dependent SFGS measurements. The data shed some light in the relation between molecular and macroscopic properties. Furthermore surface dilatational viscoelastic properties of a fluorinated amphiphile have been measured by a novel version of the oscillating bubble. The oscillating bubble method generates a non-equilibrium state by a harmonic compression and expansion of the surface layer formed at the tip of a capillary. The surface state is monitored by Surface Second Harmonic Generation (SHG).This technique is highly surface specific and discriminates between monolayer and subsurface coverage. Our set-up allows to measure the monolayer coverage under dynamic conditions and to relate this to surface dilatational viscosity and elasticity. For a purely elastic surface layer the prediction of the Lucassen van den Temple model (LvdT)are fulfilled.

Proceedings Article | 25 November 2002 Paper

Investigation of inverted and noninverted organic planar waveguide toward nonlinear optical devices

Costel Flueraru, Chander Grover, Sigurd Schrader, Hubert Motschmann

Proceedings Volume 4805, (2002) https://doi.org/10.1117/12.450897

KEYWORDS: Waveguides, Refractive index, Phase modulation, Second-harmonic generation, Nonlinear optics, Thin films, Planar waveguides, Harmonic generation, Liquids, Tunable lasers

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Proceedings Article | 7 December 2001 Paper

Phase-matched second harmonic generation and nonlinear phase shift in a Langmuir-Blodgett film waveguide

Sigurd Schrader, Costel Flueraru, Hubert Motschmann, Ludwig Brehmer

Proceedings Volume 4461, (2001) https://doi.org/10.1117/12.449835

KEYWORDS: Second-harmonic generation, Refractive index, Phase shifts, Polarization, Harmonic generation, Nonlinear optics, Chromophores, Quartz, Glasses, Interferometry

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