Combinational Vibration Modes in HO/HDO/DO Mixtures Detected Thanks to the Superior Sensitivity of Femtosecond Stimulated Raman Scattering.

Overtones and combinational modes frequently play essential roles in ultrafast vibrational energy relaxation in liquid water. However, these modes are very weak and often overlap with fundamental modes, particularly in isotopologues mixtures. We measured VV and HV Raman spectra of HO and DO mixtures with femtosecond stimulated Raman scattering (FSRS) and compared the results with calculated spectra.

First events in the coil-to-globule transition of PVME in water: An ultrafast temperature jump - time-resolved elastic light scattering study.

Hypothesis: The coil-to-globule transition is an essential phenomenon in protein and polymer solutions. Late stages of such transitions, >1 µs, have been thoroughly studied. Yet, the initial ones are a matter of speculations.

Spontaneous versus Stimulated Surface-Enhanced Raman Scattering of Liquid Water.

We have observed for the first time the surface-enhanced (SE) signal of water in an aqueous dispersion of silver nanoparticles in spontaneous (SERS) and femtosecond stimulated Raman (SE-FSRS) processes with different wavelengths of the Raman pump (515, 715, and 755 nm). By estimating the fraction of water molecules that interact with the metal surface, we have calculated enhancement factors (EF): 4.8 × 10 for SERS and (3.

Femtosecond infrared pump-stimulated Raman probe spectroscopy: the first application of the method to studies of vibrational relaxation pathways in the liquid HDO/DO system.

We have proposed and constructed a setup for a novel method of ultrafast vibrational spectroscopy: femtosecond infrared pump-stimulated Raman probe spectroscopy. This is the first time-resolved spectroscopy providing simultaneously a sub-100 fs time resolution, a spectral resolution better than 10 cm and a spectral window covering an extremely broad range of molecular vibrations (at least: 200-4000 cm) with a "single laser shot". The new method was applied to study vibrational relaxation pathways in the liquid HDO/DO system.

Evolution of high-temperature molecular relaxations in poly(2-(2-methoxyethoxy)ethyl methacrylate) upon network formation.

Copolymers of 2-(2-methoxyethoxy)ethyl methacrylate (poly(MEOMA)) are regarded as bioinert replacements of poly(-isopropylacrylamide) in some biomedical applications. Networks of poly(MEOMA) of various architecture form thermo-responsive hydrogels. Here, we present dielectric and mechanical spectroscopy studies on segmental motions and network relaxation processes in linear poly(MEOMA) and its networks - bare network and the network grafted with short poly(MEOMA) chains.

Poly(vinyl methyl ether) hydrogels at temperatures below the freezing point of water-molecular interactions and states of water.

Water interacting with a polymer reveals a number of properties very different to bulk water. These interactions lead to the redistribution of hydrogen bonds in water. It results in modification of thermodynamic properties of water and the molecular dynamics of water.

Cooperative hydration of carboxylate groups with alkali cations.

We study the orientational dynamics of water molecules in solutions of formate salts using femtosecond mid-infrared spectroscopy. We observe that combining the formate ion with small cations like Na(+) or Li(+) leads to a cooperative effect on the water dynamics. This observation points at the formation of solvent-separated ion pairs.

Raman resonance effect in liquid water.

Raman spectroscopy is a technique preferably used for studies of water structure because the proportions of intensities of main OH stretching modes are thought to reflect well a network of "intermonomer" hydrogen bonds as well as its disturbance by the presence of some solutes. The work presented herein demonstrates how the intensity ratio of two main components (around 3200 and 3400 cm (-1)) depends on the excitation wavelength in the visible range. Polarized Raman spectra indicate that the component at ca.