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Chemicals, plastics and rubber industries

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Vibronic coupling in the ground and excited states of oligoacene cations

Article Abstract:

The vibrational coupling in the ground and excited states of positively charged naphthalene, anthracene, tetracene, and pentacene molecules is studied on the basis of a joint experimental and theoretical study of ionization spectra using high-resolution gas-phase photoelectron spectroscopy and first-principles correlated quantum-mechanical calculation. Findings show that while main contribution to relaxation energy in the ground state of oligoacene systems comes from high-energy vibrations, the excited-state relaxation energies show a significant redistribution toward lower-frequency vibrations.

Quantum theory, Quantum mechanics

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Photoinduced electron transfer reactions in a porphyrin-viologen complex: observation of S2 to S1 relaxation and electron transfer from the S2 state

Article Abstract:

Transient absorbance pump-probe spectroscopy is used in studying the photoinduced electron transfer reactions in a porphyrin-viologen complex. Results indicate relaxation from the S2 to the S1 state in the wavelength region from 430 nm to 650 nm. Electron transfer occurs directly from the S2 state since the ZnTPPS(super 4-) to MV(super 2+) electron transfer could be time resolved. The back electron transfer took place with a lifetime of 0.8 plus/minus 0.1 ps.

Research, Oxidation-reduction reaction, Oxidation-reduction reactions, Porphyrins

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Relaxation processes in semidilute solutions in polymers in liquid crystal solvents

Article Abstract:

The relaxation phenomena in a polymer/liquid crystal system, in its homogenous isotropic phase near the isotropic-isotropic, isotropic-nematic, and isotropic-smectic coexistence curve, using both polarized and depolarized photon correlation spectroscopy was investigated. The system was studied for different polystyrene molecular weights, different compositions, and different temperatures close to phase boundaries.

Polymer liquid crystals, Liquid crystalline polymers, Atomic spectroscopy, Properties, Structure

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