Spatial polarization properties, quantum

Another potentially useful feature of RFR is that its site specificity is different from that of NMR or ESR, because RFR relies on a different molecular property tensor [74]. In a precursor to RFR, called optical NMR (ONMR) [59-65], site specificity has been demonstrated at a spatial resolution corresponding to quantum dots, a dramatic demonstration of the enhancement possible with the use of circularly polarized lasers or circularly polarized microwave fields such as in RFR. 

From a systematic study of bichromophoric compounds 97-99, the importance of substituents and solvent polarity in intramolecular deactivation processes of photoexcited anthracenes by nonconjugatively tethered, and spatially separated, aromatic ketones in their electronic ground state is apparent. For 97a-d, in which the electron acceptor properties of the aromatic ketone moiety have been varied by appropriate p-substitution of the phenyl ring (R is methoxy, H, phenyl, and acetyl, respectively), the longest-wavelength absorption maximum band lies at 388 nm, i.e., any ground state effects of substitution are not detectable by UV spectroscopy. Also, the fluorescence spectra of 97a-d in cyclohexane are all related to the absorption spectra by mirror symmetry. However, the fluorescence quantum yields for 97a-d in cyclohexane dramatically are substituent dependent (see Table 19), ranging from 0.20 for the methoxy derivative to 0.00059 for the acetyl compound [33,109],... 

Fundamental properties, such as the van der Waals volume, cohesive energy, heat capacity, molar refraction and molar dielectric polarization, are directly related to some very basic physical factors. Specifically, materials are constructed from assemblies of atoms with certain sizes and electronic structures. These atoms are subject to the laws of quantum mechanics. They interact with each other via electrical forces arising from their electronic structures. The sizes, electronic stmctures and interactions of atoms determine their spatial arrangement. Finally, the interatomic interactions and the resulting spatial arrangements determine the quantity and the modes of absorption of thermal energy. 

Reagent properties. In which way is the reaction influenced by properties such as reagent quantum state, velocity or light polarization (which induces spatial orientation of the particle in resonance with the radiation) ... 

Another class of spatial multi-scale methods concerns the quantum chemistry community where efforts have been focussed on the combination of quantum mechanics (QM) methods with continuum electrostatic theories in order to realistically represent the solvation free energy in a polar environment. These methods have been refined over the years and can now give a reasonable description of solvation properties of an isotropic and homogeneous medium. However, these continuum models are not appropriate to represent the electrostatic and steric interactions of the structured environment with the active site. This is particularly true in the descriptions of complex systems like enzymes or catalysts. An appropriate description of such systems has been developed using a hybrid quantum mechanical/molecular mechanical (QM/MM) approaches where the QM methods are used to describe the active site where chemical reactions or electronic excitations occur, and MM methods are employed to capture the effect of the environment on the active site. 

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