[The Effect of the Phase on Characteristic Energy of All-Trans-ß-Carotene].

All-trans-ß-carotene has important functions of light collection and light protection, and it is also an important electrooptical material. The Raman spectra of polyenes are a result of the modulation effect of the π electron energy gap on the vibration of CC bonds, which associate with the external field. So it has higher theoretical significance and practical value to study the molecular structure and properties change under the external field. Ultraviolet-visible absorption spectra and resonant Raman spectra of all-trans-ß-carotene in cyclohexanol were measured from 341 to 275 K. The liquid-solid phase transition of the sample appears at 295 K. The characteristic energy describes the conformational change of all-trans-ß-carotene molecule. After the solution phase transition, the characteristic energy ε of all-trans-ß-carotene molecule becomes bigger. And when temperature decreasing, the rate of change of the Huang-Rhys, the wavelength of UV absorption peak, electron-phonon Parameter, RSCSs of the CC bond increase. the Huang-Rhys in solid phase is an order of magnitude higher then liquid phase. The characteristic energy of liquid is 0.206 7 eV. The characteristic energy of liquid is 0.559 6 eV. The increasing of the characteristic energy ε makes the rate of increasing of the effectively conjugated length becomes bigger. The decreasing of the π electric energy gap quickens. The function of moderation from electron energy gap to all-trans-ß-carotene molecule enhances. Electron-phonon Parameter increases. RSCSs of the CC bond substantially increases.

[Study on the Turning Effect of the Energy Gap of π Electron on Atomic Vibration in Conjugated Linear Polymer].

The Visible absorption and Raman spectra of ß-carotene were measured in dimethyl sulfoxide in temperature ranging from 81 to 25 ℃ and in carbon disulfide in pressure range from 0.04 to 0.60 GPa, respectively. The results indicated that the visible absorption and Raman spectra are both red-shifted, Raman scattering cross section increase with the temperature decreasing. And with the pressure increasing, the visible absorption spectra are red-shifted, but the frequency shift towards higher frequencies in the Raman spectra, the Raman scattering cross section decrease unexpectedly. The latter can't be explained by the model of "effective conjugation length" and "coherent weakly damped electron-lattice vibrations". In this paper, we combined electron-vibration coupling rule with theoretical calculations and found that the electron-phonon coupling constant had a certain changing trend with the temperature and pressure variation, which Indicate that the interaction between π-electron and CC bond vibration was essential for this experiment result. Thus, the turning effect of energy gap of the π on CC vibration mode is responsible for such phenomenon.

[Resonance Raman Spectral Properties Studies of Beta-carotene in Solution].

Beta-carotene is an important kind of polyene biomolecules, which has significant applications on researching optoelectronic and functional materials. In-situ high pressure Raman spectra of beta-carotene are measured in CS2 solution and water respectively at pressure range from 0-0.60 GPa. Then we compared both of them the Raman shift and CC bond of the full width at half maximum (FWHM) of the Raman spectra. It is therefore concluded that both of the samples' Raman shift moved to the high wave number and the full width at half maximum increased depending of the pressure. The experiment phenomena were interpreted by the theory of "coherent weakly damped electronic-lattice vibration model" and "effective conjugation length model". The mechanism is that the beta-carotene is compressed and has the lower structure order, shorte the effective conjugation length, decreased Raman active, weaker the coherent weakly damping CC bond vibration in high pressure. Because of the CC bond length become short, so the Raman spectra are found to blueshift. The CC bond of the full width at half maximum (FWHM) of the Raman spectra increased is attributed to the increase of difference in C--C and C==C bond lengths. Moreover, due to dissolving in non-polar CS2 solvent, the beta-carotene encounters the interaction of the surrounding solvent molecules. So the dispersion force interaction between solute and solvent is more sensitive to pressure. Then it makes that the slop of Raman shift and the full width at half maximum in the CS2 solution are faster than dissolved in water with increasing pressure. This paper provides an application value for research on molecular structure change under the external field and the presence form of polyenes biomolecules in the solvent.

[Effect of pressure on electron-phonon coupling constants of all-trans-beta-carotene].

The present paper cited that R Tubino and other people introduced a kind of electron-phonon coupling constants with dimension, which can establish the relation with the Huang-Rhys factor and calculate the electron-phonon coupling constants of every C-C bond vibration mode. There are many reports about the visible absorption and Raman spectra of all-trans-beta-carotene with pressure. But the study about the Raman scattering cross section and the Huang-Rhys factor with pressure have not been reported now. Visible absorption and Raman spectra of all-trans-beta-carotene were measured in carbon disulfide in the pressure range from 0. 04 to 0. 60 GPa. The results indicated that the visible absorption spectra of beta-carotene in nonpolar solvent carbon disulfide are red-shifted with pressure increasing, but the frequency shifts towards higher frequencies in the Raman spectra, the Raman scattering cross section decreases, Huang-Rhys factor increases, and the electron-phonon coupling constants of CC bond vibration modes increase. The mechanism is that all-trans-beta-carotene caused by compression and a decrease in the structurally ordered properties of the molecules leads to narrow energy gap of the pi, shortens effective conjugation length, hinders delocalization of pi-electron, decreases the Raman scattering cross section, and increases the Huang-Rhys factor and the electron-phonon coupling constants.