Standardless spectrochemical analysis and direct simulations of time-resolved vibronic spectra of polyatomic molecules, isomers and mixtures

The efficient method for calculation of dynamical time-resolved vibronic spectra of polyatomic molecules is proposed. It allows to perform direct real-time computer simulations of such spectra for models of complex compounds, isomers and multicomponent mixtures with quantum beats and non-radiative vibrational relaxation taken into account. The examples of calculated spectra show the ways of how to search and select optimal experimental conditions and retrieve the most informative data for solution of inverse spectral problems in different situations. The new method of standardless analysis based on time-resolved vibronic spectroscopy has been developed and its main ideas are presented here. This method is able to solve quantitative and qualitative spectrochemical problems for individual substances and multicomponent mixtures (even for species with similar optical properties) with the use of experimentally measured relative intensities of dynamical spectra only. The algorithms of how to perform analysis in various experimental conditions are proposed.     

The emission of α,ω-diphenylpolyenes: A model involving several molecular structures

Available photophysical evidence for the emission of α,ω-diphenylpolyenes is shown to be consistent with a previously reported model [J. Catalán, J.L.G. de Paz, J. Chem. Phys. 124 (2006) 034306] involving two electronically excited molecular structures of 1B_u and C_s symmetry, respectively. The 1B_u structure is produced by direct light absorption from the all-trans form of the α,ω-diphenylpolyene in the ground state and its emission exhibits mirror symmetry with respect to the absorption of the compound. On the other hand, the C_s structure is generated from the 1B_u structure of the α,ω-diphenylpolyene by rotation about a C–C single bond in the polyene chain, its emission being red-shifted with respect to the previous one and exhibiting markedly decreased vibrational structure. At room temperature, both emissions give the excitation spectrum, which are ascribed to the first absorption band for the compound.