Quantum dynamics in strong fluctuating fields

A large number of multifaceted quantum transport processes in molecular systems and physical nanosystems can be treated in terms of quantum relaxation processes which couple to one or several fluctuating environments. A thermal equilibrium environment can conveniently be modelled by a thermal bath of harmonic oscillators. An archetype situation provides a two-state dissipative quantum dynamics, commonly known under the label of a spin-boson dynamics. An interesting and nontrivial physical situation emerges, however, when the quantum dynamics evolves far away from thermal equilibrium. This occurs, for example, when a charge transferring medium possesses nonequilibrium degrees of freedom, or when a strong time-dependent control field is applied externally. Accordingly, certain parameters of underlying quantum subsystem acquire stochastic character. Herein, we review the general theoretical framework which is based on the method of projector operators, yielding the quantum master equations for systems that are exposed to strong external fields. This allows one to investigate on a common basis the influence of nonequilibrium fluctuations and periodic electrical fields on quantum transport processes. Most importantly, such strong fluctuating fields induce a whole variety of nonlinear and nonequilibrium phenomena. A characteristic feature of such dynamics is the absence of thermal (quantum) detailed balance.Comment: review article, Advances in Physics (2005), in pres

FOURIER TRANSFORM RAMAN STUDY OF STRUCTURE REARRANGEMENT IN ELECTROCHROMIC CRYSTALLINE HYDRATE THIN FILMS WO3n(H2O)WO_{3}n(H_{2}O) DURING COLORATION-BLEACHING PROCESS.

Author Institution: Institute of Physics, pr. Nauki 46, Kiev, 252022, UkraineAn electrochromic phenomena in transition metal oxides have been very widely studied. This unique phenomenon of electrically induced reversible coloration and charge storage in the films has many applications. It is extremely important to study colored material state for understanding of electrochromic coloration mechanism. The usual techniques are not able to be used during the polarization of a sample in an electrolyte medium for the investigation of the neighboring environment changes in the films. Fourier Transform Raman Spectroscopy gives unique possibilities to carry out in situ measurements in electrochemical cell. The electrochromic crystalline hydrate thin films $WO_{3}n(H_{2}O)$ (n=1/3: 2) have been studied to clarify the influence of injected protons and electrons on the film structure during the electrochromic coloration-bleaching process with FT Raman Spectroscopy for the first time. FT Raman spectra of thin films $WO_{3}n(H_{2}O)$ in colored and bleaching states were measured in the region $100-3500 cm^{-1}$ on a Bruker IFS 88 FT - IR spectrometer with FT Raman module using Nd : YAG laser (1.064 mkm). The $H^{+}$ and $D^{+}$ ions from aqueous electrolyte were used for the film coloration. The injected charge density varies from 1 to $30 mC/cm^{2}$. It was shown that protons and deuterons inserted into the film lattice during electrochromic coloration do not play passive role of the charge compensators as considered early but strongly interact with the films and result in structure rearrangement

PHOTOSENSITIZATION OF HETEROGENEOUS NANOSTRUCTURED METAL OXIDE FILMS WITH DYES MOLECULES

Author Institution: Department of Chemistry, SUNY at PotsdamThe photosensitization is a powerful method used to extent the photoresponse of a wide-bandgap semiconductor into the visible region of the spectrum. These process has a paramount importance in application for solar energy conversion. The photocurrent spectroscopy was used to study heterogeneous photoelectrodes of the porous $WO_{3}$ film/nanoparticulate $TiO_{2}$ film. Dependencies on wavelengths and applied potential were investigated in order to explore the charge photogeneration process. Photocurrent spectra and cyclic voltammogramms are recorded in a three-electrode cell. The source is 400 W Xe lamp coupled to a SPEX monochromator. The monolayer of adsorbed dyes (cresyl violet, thionine and rhodamine B) was used for photosensitization process. The nanoparticle size, film morphology and structure were tested with scanning and transmttance electron microscopy. The density and thickness of the deposited films were determined with a Electrochemical Quartz Crystal (EQCN). The band gap energy for $WO_{3}$ and $TiO_{2}$ films was determined from the spectral distribution of photocurrent. The comparative analysis of photoelectrochemical properties of $WO_{3}/TiO_{2}$ heterogeneous photoelectrodes and one-component photoelectrodes of $WO_{3}$ and $TiO_{2}$ has been carried out at the front side illumination of the films. A very promising increase of photocurrent (in the 2-10 times) in heterogeneous photoelectrodes at supraband illumination and subband illumination with photosensitization by adsorbed dyes was observed. The heterogeneous structure of porous nanocrystalline $WO_{3}$ oxide films/nanoparticulate $TiO_{2}$ film allows one to improve charge separation process and increase photogeneration efficiency. Improvement of charge separation can be expected due to electron transfer from conduction band of $TiO_{2}$ nanoparticles to the lower lying conduction band of nanocrystalline oxide film

Novel chelate-induced magnetic alignment of biological membranes.

A phospholipid chelate complexed with ytterbium (DMPE-DTPA:Yb3+) is shown to be readily incorporated into a model membrane system, which may then be aligned in a magnetic field such that the average bilayer normal lies along the field. This so-called positively ordered smectic phase, whose lipids consist of less than 1% DMPE-DTPA:Yb3+, is ideally suited to structural studies of membrane proteins by solid-state NMR, low-angle diffraction, and spectroscopic techniques that require oriented samples. The chelate, 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine diethylenetriaminepentaacetic acid, which strongly binds the lanthanide ions and serves to orient the membrane in a magnetic field, prevents direct lanthanide-protein interactions and significantly reduces paramagnetic shifts and line broadening. Similar low-spin lanthanide chelates may have applications in field-ordered solution NMR studies of water-soluble proteins and in the design of new magnetically aligned liquid crystalline phases