Quantitative measurements of vibrational Raman depolarization ratios have been used to study molecular orientational order in nematic and for the first time, in smectic liquid crystals. Temperature dependence of the depolarization ratios of the terminal C≡N and the central biphenyl link vibrational bands of two alkylcyanobiphenyl compounds (CBn) and a cyclohexane derivative (PCH7) has been investigated extensively. Two experimental technics have been used: a conventional triple monochromator and the Raman microprobe to overcome the spurious depolarization due to the long wave director fluctuations. The orientational order parameters <P2≳ and <P4≳ were then calculated. The results have been discussed assuming repulsive forces are dominant for the CBn compounds and using the Maïer–Saupe theory in the case of PCH7.

Resonance hyperRaman scattering polarization. A measure of methyl iodide Bstate subpicosecond lifetimes J. Chem. Phys. 98, 150 (1993); 10.1063/1.464665Single particle reorientation and pair correlations of methyl iodide solutions studied by depolarized Rayleigh and Raman scattering

Under ultraviolet (UV) illumination of GaAs with photon energies above 3.5 eV, Si–H complexes are known to be efficiently dissociated at room temperature. Studying the dissociation kinetics of Si–H and Si–D complexes in GaAs, we have observed that, for a given incident UV photon density, the concentration of dissociated Si–D complexes is 10–20 times below the concentration of dissociated Si–H complexes. This strong isotope effect is discussed under the light of recent excitation models of Si–H(D) bonds at the surface of silicon and at the Si/SiO2 interface.