Spectroscopic Studies of Liquid Structure and Solvation

Erika Kalman and Gabor Palinkas were married in 1974 and have two children. 

Spectroscopy involves the study of the interactions of electromagnetic radiation with matter. In the case of liquids, radiation of a wide range of frequencies, and thus energies, has been used, all the way from radio-frequency waves to X-rays. Experiments involving neutrons, which are associated with very short wavelengths, are also important. In the spectroscopic experiment the incident radiation may be either absorbed or scattered and the experimental information is obtained by examining the intensity and direction of the radiation after it has passed through the sample. 

One should remember that the atoms and molecules in liquids are not motionless but in a state of flux determined by the intermolecular interactions and temperature. From the study of microwave spectroscopy discussed in chapter 4, it was found that rotational diffusion processes in liquids are characterized by relaxation times the order of a few picoseconds. When a liquid is irradiated with UV or visible radiation which involves frequencies greater than 10 Hz, the atoms and molecules appear to be motionless because the frequency of the electromagnetic radiation is much greater than that associated with molecular motion (10 Hz and lower). The same is true for infrared spectroscopy except in the 

In this chapter much of the discussion involves electrolyte solutions in both aqueous and non-aqueous media. The role of spectroscopy in elucidating the chemical interactions which cannot be understood on the basis of classical electrostatics is emphasized. More details about each of the four spectroscopic techniques and their application are now given. 

The quantity of interest in a diffraction experiment is the intensity 7(0) observed at a scattering angle 0 or at wave number ko defined as 

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Alcohols exhibit a bifunctional nature in aqueous solution. On the one hand, there exists a hydrophobic hydrocarbon group which resists aqueous solvation on the other, there is the hydrophilic hydroxyl group which interacts intimately with the water molecules. Franks and Ives (30, 31) have reviewed experimentation and theoretical treatises on the structure of water, the structure of liquid alcohols, and the thermodynamic, spectroscopic, dielectric, and solvent properties and P-V-T relationships of alcohol-water mixtures. Sada et al. (27) reviewed, in particular, the salt effects of electrolytes in alcohol-water systems and discussed the various correlations of the salt effect applied to these systems. Inorganic salts were used almost universally in these salt effect studies. 

The proceedings of a conference on metal-ammonia solutions have been published, featuring reviews of the physical properties of dilute and concentrated solutions, electrical, n.m.r., i.r., and Raman spectroscopic studies of diffusion, the solvated electron, kinetics, and solution structure."" Electron spin resonance in metallic Li-NHa systems has been investigated from 12 to 296 K. In the liquid solutions and in the cubic phase of Li(NH3)4 the conduction e.s.r. lineshapes are in agreement with theory. To a good approximation the solvated ions are the only spin scatterers in the liquid state. The paramagnetic susceptibility of liquid Li(NH3)4 indicates that the concentration of localized moments is low and they order antiferromagnetically below 20 K." ... 

In COlL-1, all of the main aspects of the liquid-state structure of room-temperature ionic liquids were already laid out in contributions by several groups, although sometimes still in an incipient way. Hardacre and co-workers reported neutron diffraction studies of short-chain dialkylimidazolium ionic liquids, perfectly illustrating the charge ordering and n-interactions [17]. They also used different spectroscopic and simulation methods to study how the solvation of aromatic and polar molecules (benzene and ethanenitrile, respectively) in the ionic liquids modifies the structure of the media [46] and the balance between the different terms in the interactions coulombic, van der Waals (dispersive), hydrogen bonds and multipolar. 

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