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The orientation of molecules in the monomolecular stearamide monolayers has been studied by infrared linear dichroism. By comparing the transmission absorption spectra carried out at different angles of incidence with the reflection absorption spectra obtained by depositing the monolayers on a metal substrate, the orientation of the dipole transition moments for a great number of normal vibration modes of the molecules may be determined to within a few degrees accuracy. Given certain assumptions, the orientation of the molecules themselves can then be deduced.

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The emission spectrum of a plasma of silane flowing through a multipass reactor and excited by a radio frequency discharge has been recorded with a high information Fourier transform spectrometer. 192 rovibrational transitions of the 28SiH radical, between 1800 and 2150 cm−1, have been measured in the electronic ground state. These transitions are related to the fundamental band 1–0 and the two hot bands 2–1 and 3–2. A least squares procedure have led to the determination of a unique set of 25 accurate molecular constants for the vibrational levels v=0, 1, 2, 3 of the X 2Π state. The standard deviation on the calculated frequencies is 7×10−4 cm−1.

A joint work on morphology, structure, and nonlinear optical properties of vacuum evaporated thin films of pDCH on different amorphous or monocrystalline substrates is presented. The thin film evaporation of some diacetylene monomers on the alkali-halide single crystals leads to epitaxy with particularly good biorientation of the polymer chains, the b repetitive distance of the monomer matches well with two equivalent [110] and [1̄10] directions of the cubic KBr cystal. Polymerization is thermally induced. The resulting pDCH films are polycrystalline with low optical defects. Crystal sizes are in the range of 0.1 to 0.3 μm with some long needles of 2–3 μm length. Third harmonic generation (THG) and electric field induced second harmonic generation (EFISHG) measurements on disordered thin films show the two-photon resonances at 1.35–1.45 μm wavelength range, similarly as in other polydiacetylenes, with resonant values 〈χ(3) (−3ω; ω,ω,ω)〉=(1±0.1)×10−10 esu (THG) and 〈χ(3) (−2ω, ω,ω,0)〉=(6.4±0.4)×10−11 esu (EFISHG). The biorientational order of the pDCH chains observed by electron microscopy on various alkali-halide single crystals is confirmed on a macroscopical scale by third harmonic generation. As expected for a bioriented film, the angular dependence of THG intensity follows the theoretical law. So, for the first time, both morphological and optical techniques have been used in combination to characterize thin films and have shown a nearly perfect biorientation of the polymer crystals.