A Semiclassical Theory of a Dissipative Henon—Heiles System

A semiclassical theory of a dissipative Henon—Heiles system is proposed. Based on -scaling of an equation for the evolution of the Wigner quasiprobability distribution function in the presence of dissipation and thermal diffusion, we derive a semiclassical equation for quantum fluctuations, governed by the dissipation and the curvature of the classical potential. We show how the initial quantum noise gets amplified by classical chaotic diffusion, which is expressible in terms of a correlation of stochastic fluctuations of the curvature of the potential due to classical chaos, and ultimately settles down to equilibrium under the influence of dissipation. We also establish that there exists a critical limit to the expansion of phase space. The limit is set by chaotic diffusion and dissipation. Our semiclassical analysis is corroborated by numerical simulation of a quantum operator master equation.     

Effect of methylation to an ethylenediamine receptor-based fluorescence signaling system: Solvent dependence, metal ion selectivity and photophysical studies

A fluorescence signaling system (L₁) has been synthesized in the format, ‘fluorophore-spacer-receptor’ with an ‘amino-alkyl-amino’ group as the receptor where an anthracene and a 2,4-dinitrobenzene moieties are attached at two ends. As evident from the photophysical behavior of this system, attachment of methyl groups to the donor N atoms not only increases the charge-transfer character of the signaling system, but imparts structural rigidity and perturbs the binding ability of the receptor core, that results in selective fluorescence enhancement in presence of Zn(II). Solid-state structure of L₁ is determined by X-ray crystallography.     

Biomimetic multifunctional porous chalcogels as solar fuel catalysts

Biological systems that can capture and store solar energy are rich in a variety of chemical functionalities, incorporating light-harvesting components, electron-transfer cofactors, and redox-active catalysts into one supramolecule. Any artificial mimic of such systems designed for solar fuels production will require the integration of complex subunits into a larger architecture. We present porous chalcogenide frameworks that can contain both immobilized redox-active Fe(4)S(4) clusters and light-harvesting photoredox dye molecules in close proximity. These multifunctional gels are shown to electrocatalytically reduce protons and carbon disulfide. In addition, incorporation of a photoredox agent into the chalcogels is shown to photochemically produce hydrogen. The gels have a high degree of synthetic flexibility, which should allow for a wide range of light-driven processes relevant to the production of solar fuels.     

The role of interplay between the potential and the ambient energies on the vibration energy harvesting

In this paper we have demonstrated how the conversion of the ambient energy into the electrical energy depends on the properties of the ambient energy and the mechanical oscillator. We have observed that the conversion of the vibration energy into the electrical energy may be good if the voltage can follow closely the evolution of of the amplitude of the oscillator. Thus if the voltage and the position fluctuate in a correlated manner then the conversion of the ambient energy into the electrical energy is good. Our another observation is that for a given capacitance, the power transferred (PT) from the oscillator to the transducer may be maximum in the variation of PT with increase in resistance, R. In other words, the power transferred changes with a maximum as the capacitance, C grows for a fixed value of the resistance. Along with these we have investigated how the other relevant quantities such as the efficiency of the energy transferred process depends on the characteristics of the oscillating systems, the environment and the piezoelectric dynamics.     

Noise correlation-induced splitting of Kramers' escape rate from a metastable state

A correlation between two noise processes driving the thermally activated particles in a symmetric triple-well potential may cause a symmetry breaking and a difference in relative stability of the two side wells with respect to the middle one. This leads to an asymmetric localization of population and splitting of Kramers' rate of escape from the middle well, ensuring a preferential distribution of the products in the course of a parallel reaction.