Solvent band shape function

Equation [48] gives the Franck-Condon factor that defines the probability of finding a system configuration with a given magnitude of the energy gap between the upper and lower CT free energy surfaces. It can be directly used to define the solvent band shape function of a CT optical transition in Eq. [134]... 

The Franck-Condon factors of polarizable chromophores in Eq. [153] can be used to generate the complete vibrational/solvent optical envelopes according to Eqs. [132] and [134]. The solvent-induced line shapes as given by Eq. [153] are close to Gaussian functions in the vicinity of the band maximum and switch to a Lorentzian form on their wings. A finite parameter ai leads to asymmetric bands with differing absorption and emission widths. The functions in Eq. [153] can thus be used either for a band shape analysis of polarizable optical chromophores or as probe functions for a general band shape analysis of asymmetric optical lines. 

In these measurements, dynamic processes have been analyzed primarily by probing a transient absorption at one wavelength. In general, however, absorption spectra of excited states and chemical intermediates overlap each other. Furthermore, conformational change and orientational relaxation of the surrounding solvent molecules result in a time-dependence of the spectral band shape. For example, intramolecular exciplex systems give an absorption spectrum, the band shape of which is a function of solvent properties and delay times... 

Fig. 5 Electronic transitions of [Re(Cl)(CO)3(bpy)] calculated in vacuum (a), acetonitrile (b), simulated absorption spectra in vacuum (c, dashed) and acetonitrile (c, full), and experimental absorption spectrum measured in acetonitrile (d). It follows that successful TD-DFT simulation of the absorption spectrum and singlet CT states requires using hybrid functionals and continuum dielectric models for the solvent [11, 33], Calculation TD-DFT G03/PBE0, CPCM for MeCN. Simulation All calculated transitions included. Gaussian shapes (jwhm = 0.4 eV cm- ) of the absorption bands are assumed. Band areas are proportional to calculated oscillator strengths. Simulated using the GaussSum software. Reprinted with permission from [33]...

The sensitivity of vibrational spectroscopy allows interactions of polyelectrolytes and surfactants to be monitored in aqueous and nonaqueous solutions. The solubilization and conformational properties of a comb-shaped copolymer of 1-octadecane-co-maleic anhydride in aqueous solution in the presence and absence of SDS depend on the degree of ionization of the copolymer (2i). The C-H stretching region of the Raman spectrum is sensitive to such interactions. Figure 11 illustrates how the C-H stretching band shifts as a function of solvent (in this case water and heptane). 

The absorption spectra of 2, presented in Figure 2.1a as a function of the water content in an ethanol/water solvent mixture, has led to the qualitative conclusion that the enol form b dominates in ethanol while the keto form a is stabilized by water. It is obvious that the spectra are solvent dependent with respect to the shape, which is clear at least from the shift in the position of the keto band at 480nm (Figure 2.1b), and the only possibility for quantitative analysis is to use band areas instead of the spectra. 

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