Theoretical descriptions of two-dimensional (2D) vibrational and electronic spectroscopy are presented By using a coupled multi-chromophore model, some examples of 2D spectroscopic studies of peptide solution structure determination and excitation transfer process in electronically coupled multi-chromophore system are discussed A few remarks on perspectives of this research area are given

Coherent Two-Dimensional Optical Spectroscopy

We report the frequency-dependent optical constants, n(ν) and α(ν), or, equivalently, the complex permittivity e(ω) = e‘(ω) − ie‘‘(ω), over the frequency range from 2 to 50 cm-1 for water, methanol, ethanol, 1-propanol, and liquid ammonia. These spectra have been measured with femtosecond terahertz pulse transmission spectroscopy. These liquids exhibit multiple-Debye behavior, making their frequency-dependent dielectric constants valuable benchmarks for molecular dynamics simulations and other theoretical treatments of liquids.

Far-infrared dielectric properties of polar liquids probed by femtosecond terahertz pulse spectroscopy

The dynamics of solvation in polar liquids

Hybrid lead halide perovskites exhibit carrier properties that resemble those of pristine nonpolar semiconductors despite static and dynamic disorder, but how carriers are protected from efficient scattering with charged defects and optical phonons is unknown. Here, we reveal the carrier protection mechanism by comparing three single-crystal lead bromide perovskites: CH3NH3PbBr3, CH(NH2)2PbBr3, and CsPbBr3. We observed hot fluorescence emission from energetic carriers with ~102-picosecond lifetimes in CH3NH3PbBr3 or CH(NH2)2PbBr3, but not in CsPbBr3. The hot fluorescence is correlated with liquid-like molecular reorientational motions, suggesting that dynamic screening protects energetic carriers via solvation or large polaron formation on time scales competitive with that of ultrafast cooling. Similar protections likely exist for band-edge carriers. The long-lived energetic carriers may enable hot-carrier solar cells with efficiencies exceeding the Shockley-Queisser limit.

https://science.sciencemag.org/content/sci/353/6306/1409.full.pdf

Screening in crystalline liquids protects energetic carriers in hybrid perovskites

Two of the more fundamental ways in which molecules change their behavior when they are dissolved are that they can begin to exchange energy with the surrounding liquid and they can induce their surroundings to rearrange so as to provide a significant stabilizing influence. The first of these is typified by the process of vibrational population relaxation of a vibrationally hot species. The second conceptcritical to solution chemistryis what is known as solvation. Both of these processes are sufficiently fundamental that one would really like to know, at the most mechanical and molecular level possible, just what events are required in order to make them happen. But how difficult is it going to be to extract such molecular detail from the complicated many-body dynamics? The most microscopic level of understanding one could ever hope to possess might seem far removed from the finely detailed dynamical information which is available routinely for individual isolated molecules and for molecule−molecule colli...

Nonreactive Dynamics in Solution: The Emerging Molecular View of Solvation Dynamics and Vibrational Relaxation

The time-resolved optical Kerr responses of several simple molecular liquids are probed with 65-fs laser pulses. Four dynamically distinct responses associated with the nonlinear susceptibility are observed in every liquid that possesses a permanent anisotropic polarizability. A simple model that specifically includes inertial effects provides an excellent description of the entire temporal profile of the Kerr signal of each liquid investigated. The role of coherent-coupling effects in the interpretation of optical Kerr data is outlined both experimentally and theoretically. >

Femtosecond optical Kerr studies on the origin of the nonlinear responses in simple liquids

Femtosecond laser-induced Kerr responses in liquid carbon disulfide

Femtosecond laser-induced optical kerr dynamics in CS2/alkane binary solutions

Femtosecond dynamics of the optical Kerr effect in liquid nitrobenzene and chlorobenzene

Sites at which excess electrons in pure water at 10 °C could become initially localized and subsequently rapidly solvated are identified by scanning a molecular dynamics simulation of pure equilibrium ST2 water with a test charge. Very favorable sites with respect to both volume and electrostatic potential are found in relatively high number density. Although the observed distribution of large cavities spans a wide range with respect to the electrostatic potential at the cavity centers, the calculated potential energy at the most favorable sites is almost as large as the apparent hydration energy of the electron in the equilibrated state.

Geraldine A. Kenney-Wallace

Papers

Femtosecond optical Kerr studies on the origin of the nonlinear responses in simple liquids

Femtosecond laser-induced Kerr responses in liquid carbon disulfide

Femtosecond laser-induced optical kerr dynamics in CS2/alkane binary solutions

Femtosecond dynamics of the optical Kerr effect in liquid nitrobenzene and chlorobenzene

Electron localization in liquid water: A computer simulation study of microscopic trapping sites