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The pressure-induced molecular dissociation as one of the fundamental problems in physical sciences has aroused many theoretical and experimental studies. Here, using a newly developed particle swarm optimization algorithm, we investigate the high-pressure-induced molecular dissociation. The results show that the carbon tetrachloride (CCl4) is unstable and dissociates into C2Cl6 and Cl2 under approximately 120 GPa and more. The dissociation is confirmed by the lattice dynamic calculations and electronic structure of the Pa3 structure with pressure evolution. The dissociation pressure is far larger than that in the case of high temperature, indicating that the temperature effectively reduces the activation barrier of the dissociation reaction of CCl4. This research improves the understanding of the dissociation reactions of CCl4 and other halogen compounds under high pressures. [ABSTRACT FROM AUTHOR]

We report on a temperature-dependent resonance Raman spectral characterization of the polyene chain of canthaxanthin. It is observed that all vibrational intensities of the polyene chain are inversely proportional to temperature, which is analyzed by the resonance Raman effect and the coherent weakly damped electron/lattice vibrations. The increase in intensity of the CC overtone/combination relative to the fundamental with temperature decreasing is detected and discussed in terms of electron/phonon coupling and the activation energy Uop. Moreover, the polyene chain studies using the density functional theory B3LYP/6-31G* level reveal a prominent peak at 1525 cm−1 consisting of two closely spaced modes that are both dominated by C=C stretching coordinates of the polyene chain. [ABSTRACT FROM AUTHOR]

Temperature dependencies (81 ?C-18 ?C) of visible 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. [ABSTRACT FROM AUTHOR]

The effects of an anti-hydrogen bond on the v1-v12 Fermi resonance (FR) of pyridine are experimentally investigated by using Raman scattering spectroscopy. Three systems, pyridine/water, pyridine/formamide, and pyridine/ carbon tetrachloride, provide varying degrees of strength for the diluent-pyridine anti-hydrogen bond complex. Water forms a stronger anti-hydrogen bond with pyridine than with formamide, and in the case of adding non-polar solvent carbon tetrachloride, which is neither a hydrogen bond donor nor an acceptor and incapable of forming a hydrogen bond with pyridine, the intermolecular distance of pyridine will increase and the interaction of pyridine molecules will reduce. The dilution studies are performed on the three systems. Comparing with the values of the Fermi coupling coefficient W of the ring breathing mode v1 and triangle mode v12 of pyridine at different volume concentrations, which are calculated according to the Bertran equations, in three systems, we find that the solution with the strongest anti-hydrogen bond, water, shows the fastest change in the v1-v12 Fermi coupling coefficient W with the volume concentration varying, followed by the formamide and carbon tetrachloride solutions. These results suggest that the stronger anti-hydrogen bond-forming effect will cause a greater reduction in the strength of the v1-v12 FR of pyridine. According to the mechanism of the formation of an anti-hydrogen bond in the complexes and the FR theory, a qualitative explanation for the anti-hydrogen bond effect in reducing the strength of the v1-v12 FR of pyridine is given. [ABSTRACT FROM AUTHOR]

This paper demonstrates the second-order nonlinear hyperpolarisability γ of all-trans-β-carotene in different solvents by linear spectroscopic technique that is based on resonance Raman scattering and UV-VIS (Ultraviolet-visible) absorption spectroscopy. Owing to the two-level model well describing the link that exists between the resonance Raman scattering and stimulated Raman scattering, the stimulated Raman polarisability αR can be calculated through the two-photon resonance system. The value of γ of all-trans-β-carotene in carbon bisulfide solution is 6.435*10-33 esu(1 esu of resistance = 8:98755 * 1011 Ω) that is close to the true value, because the solution of all-trans-β-carotene in carbon bisulfide satisfies the rigid resonance Raman scattering condition. This method is expected to be worthy of applications to measure the second-order nonlinear hyperpolarisability of a conjugate organic molecule. [ABSTRACT FROM AUTHOR]

We investigate the 3PF2 neutron superfluidity in b-stable neutron star matter and neutron stars by using the BCS theory and the Brueckner-Hartree-Fock approach. We adopt the Argonne V18 potential supplemented with a microscopic three-body force as the realistic nucleon--nucleon interaction. We have concentrated on studying the three-body force effect on the 3PF2 neutron pairing gap. It is found that the three-body force effect is to enhance remarkably the 3PF2 neutron superfluidity in neutron star matter and neutron stars. [ABSTRACT FROM AUTHOR]