Water has many anomalous properties compared to "simple" liquids, and these anomalies are typically enhanced in supercooled water. While numerous models have been proposed, including the liquid-liquid critical point, singularity-free scenario, stability limit conjecture, a molecular-level understanding remains elusive.The main difficulty determining which, if any, of is correct limited amount data relevant temperature pressure ranges. For water at ambient pressures, which focus this work,...

Understanding the properties of electronically interacting molecular chromophores, which involve internally coupled electronic-vibrational motions, is important to spectroscopy many biologically relevant systems. Here we apply linear absorption, circular dichroism (CD), and two-dimensional fluorescence (2DFS) study polarized collective excitations excitonically cyanine dimers (Cy3)2 that are rigidly positioned within opposing sugar-phosphate backbones double-stranded region a (ss) -...

In this work, we use absorbance, circular dichroism (CD), and two-dimensional fluorescence spectroscopy (2DFS) to study the local conformations conformational disorder within chromophore-labeled DNA constructs.

The nonlinear optical response of a material system contains detailed information about its electronic structure. Standard approaches to spectroscopy often use multiple beams crossed in sample, and detect the wave vector matched polarization transmission. Here, we apply phase-synchronous digital detection scheme using an excitation geometry with two phase-modulated collinear ultrafast pulses. This can be used efficiently coherent signals incoherent signals, such as higher harmonics...

The presence of organic materials adsorbed to the surfaces aerosol particles has been demonstrated be a determining factor in relevant atmospheric processes. Malonic acid is small, water-soluble that common aerosols and surface-active. A comprehensive investigation adsorption malonic air/water interface was accomplished using vibrational sum frequency spectroscopy (VSFS) surface tension measurements as functions concentration pH. found weakly solvated at interface, its orientation function...

Significance Water plays a prominent role in many areas of physical and biological sciences. Water, though commonplace, is also highly unusual comparison to most liquids. Promising models explain water’s anomalous properties propose that it heterogeneous, temperature-dependent mixture two structural motifs. Key phenomena related this heterogeneity are predicted occur for deeply supercooled water where fast crystallization has prevented experiments. We use pulsed laser heating technique...

Understanding the properties of supercooled water is important for developing a comprehensive theory liquid and amorphous ices. Because rapid crystallization deeply water, experiments on it are typically carried out under conditions in which temperature and/or pressure rapidly changing. As result, information structural relaxation kinetics as approaches (metastable) equilibrium useful interpreting results obtained this experimentally challenging region phase space. We used infrared...

We have examined the structure of supercooled liquid D2O as a function temperature between 185 and 255 K using pulsed laser heating to rapidly heat cool sample on nanosecond timescale. The can be represented linear combination two structural motifs, with transition them described by logistic centered at 218 width 10 K. relaxation metastable state, which occurred prior crystallization, exhibited nonexponential kinetics rate that was dependent initial configuration. When is scaled maximum...

Experiments investigating the properties of deeply supercooled liquid water are needed to develop a comprehensive understanding water's anomalous properties. One approach involves transiently heating nanoscale films into region for several nanoseconds at time and then interrogating after they have quenched cryogenic temperatures. To relate results obtained with this other experiments simulations on water, it is important understand how closely structure tracks (metastable) equilibrium as...

The reaction coefficient for hydrogen/deuterium (H/D) exchange and the diffusion of hydrated excess protons within amorphous solid water (ASW) are characterized as a function temperature. For these experiments, films deposited on Pt(111) substrate at 108 K, reactions with pre-adsorbed hydrogen atoms produce protons. Upon heating, diffuse water, H/D occurs when they encounter D2O probe molecules in films. time-dependent concentration is monitored infrared spectroscopy, it indicates from...

We investigate the effect of phase modulation laser beams on coherent and incoherent non-linear signals arising from interaction femtosecond pulses with matter. observe that two collinear beams, whose phases are modulated by frequencies $ϕ_1$ $ϕ_2$, produce second harmonic crystals intensities at detector $ϕ_2-ϕ_1$ $2(ϕ_2-ϕ_1)$. also an action signal, such as fluorescence photocurrent, which arises absorption photons, is same in case generation. present a theoretical analysis to explain our...