Ethanol molecular vibrations

A major breakthrough in the measurement of VER occurred in 1972. Laubereau et al. (32) used picosecond laser pulses to pump molecular vibrations via stimulated Raman scattering (SRS) and time-delayed incoherent anti-Stokes probing to study VER of C-H groups in ethanol and methanol ( " -3000 cm-1). Alfano and Shapiro (33) used the same technique to monitor both the decay of the initially excited (parent) C-H stretch excitation and the appearance and subsequent decay of a daughter vibration,... 

Resonance Raman (RR) experiments have also provided valuable data on the structure of the electron. RR spectra of aqueous solvated electrons revealed enhancements of the water inter- and intra-molecular vibrations demonstrating that electronic excitation was significantly coupled to these modes. Frequency downshifts of the resonantly enhanced H2O bend and stretch were explained by charge donation into solvent frontier orbitals. RR spectra in primary alcohols (methanol, ethanol, propan-l-ol) revealed strong vibronic coupling of the solvated electron to at least five normal modes of the solvent. The spectra showed enhancements of the downshifted OH stretch. 

H. L. Fang and R. L. Swofford, Molecular conformers in gas phase ethanol A temperature study of vibrational overtones. Chem. Phys. Lett. 105, 5 11 (1984). 

Interface between two liquid solvents — Two liquid solvents can be miscible (e.g., water and ethanol) partially miscible (e.g., water and propylene carbonate), or immiscible (e.g., water and nitrobenzene). Mutual miscibility of the two solvents is connected with the energy of interaction between the solvent molecules, which also determines the width of the phase boundary where the composition varies (Figure) [i]. Molecular dynamic simulation [ii], neutron reflection [iii], vibrational sum frequency spectroscopy [iv], and synchrotron X-ray reflectivity [v] studies have demonstrated that the width of the boundary between two immiscible solvents comprises a contribution from thermally excited capillary waves and intrinsic interfacial structure. Computer calculations and experimental data support the view that the interface between two solvents of very low miscibility is molecularly sharp but with rough protrusions of one solvent into the other (capillary waves), while increasing solvent miscibility leads to the formation of a mixed solvent layer (Figure). In the presence of an electrolyte in both solvent phases, an electrical potential difference can be established at the interface. In the case of two electrolytes with different but constant composition and dissolved in the same solvent, a liquid junction potential is temporarily formed. Equilibrium partition of ions at the - interface between two immiscible electrolyte solutions gives rise to the ion transfer potential, or to the distribution potential, which can be described by the equivalent two-phase Nernst relationship. See also - ion transfer at liquid-liquid interfaces. 

In Hgl, possibility C is the best description [8]. The dephasing time constant is -150 fs and the overall time for vibrational cooling is -200 fs. Thus coherence is seen in the vibrational excited states, and in the ground state as well. A molecular dynamics simulation of rigid Hgl in ethanol was used to imderstand the VER mechanism [90]. The computed frequency-dependent friction is shown in figure C3.5 8 [90]. Notice this function is much more complicated than in liquid O2 (figure C3.5.6). and an exponential gap law is not observed. The simulation results... 

Figure C3.5.8. Computed frequency-dependent friction (inversely proportional to the VER lifetime Tj) from a classical molecular dynamics simulation of rigid Hgl molecules in ethanol solution, from [90]. The Hgl vibrational...

Gnanakaran S and Hochstrasser R M 1996 Vibrational relaxation of Hgl in ethanol equilibrium molecular dynamics simulations J. Chem. Phys. 105 3486-96... 

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