Using the pressure‐induced polarized Raman spectra of carbon tetrachloride up to 22 GPa, a significant anomalous polarization (the depolarization ratio >0.75) was observed. We analyzed it by evaluating the antisymmetric anisotropy distribution of modes in Td and explored the corresponded molecular structure having been translated from Td into a lower symmetry. The P21/c and Pa3 structures of carbon tetrachloride were optimized as a function of pressure to further confirm that the molecules deviated from regular tetrahedra. The C2v and D2 were analyzed to be candidates of the lower symmetry based on group and Landau theory.
Temperature dependencies (81 °C–18 °C) ofvisible absorption and Raman spectra of all-trans-β-carotene and all-trans-retinol extremely diluted in dimethyl sulfoxide are investigated in order to clarify temperature effects on different polyenes. Their absorption spectra are identified to be redshifted with temperature decreasing. Moreover, all-trans-β-carotene is more sensitive to temperature due to the presence of a longer length of conjugated system. The characteristic energy responsible for the conformational changes in all-trans-β-carotene is smaller than that in all-trans-retinol. Both of the Raman scattering cross sections increase with temperature decreasing. The results are explained with electron—phonon coupling theory and coherent weakly damped electron—lattice vibrations model.
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