External field control of condensed phase reactions

Springer Series in Chemical Physics, 2000

An efficient semiclassical optimal control theory for controlling wave packet dynamics on a single adiabatic potential energy surface applicable to the systems of many degrees of freedom is discussed with all the details. The approach combines advantages of different formulations of optimal control theory: quantum and classical on one hand, and global and local on the other. The efficiency and reliability of the method is demonstrated by taking the systems of two and four dimensions as examples.

Accounts of Chemical Research, 1999

Physical Review E, 2011

The role of the wave form of periodic secondary excitations at controlling (suppressing and enhancing) escape from a potential well is investigated. We demonstrate analytically (by Melnikov analysis) and numerically that a judicious choice of the excitation's wave form greatly improves the effectiveness of the escape-controlling excitations while keeping their amplitude and period fixed. These predictions are confirmed by an energy-based analysis that provides the same optimal values of the escape-controlling parameters. The example of a dissipative Helmholtz oscillator is used to illustrate the accuracy of these results.

Engineering of Chemical Complexity II, 2014

Besides the well-known Turing patterns, reaction-diffusion (RD) systems possess a rich variety of spatio-temporal structures [Kuramoto (1984); Mikhailov (1990); Kapral and Showalter (1995)]. Spatially one-dimensional examples include traveling fronts, solitary pulses, and periodic pulse trains that are the building blocks of more complicated patterns in two-and three-dimensional active media as, e.g., spiral and scroll waves, respectively. Another important class of RD patterns forms stationary, breathing, moving or self-replicating localized spots. Labyrinthine patterns as well as phase turbulence, defect-mediated spiral and scroll wave turbulence are examples for more complex patterns. In the Belousov-Zhabotinsky (BZ) reaction in microemulsions the BZ inhibitor (bromide) is produced in nanodroplets and diffuses through the oil phase at a rate up to two orders of magnitude greater than that of the BZ activator (bromous acid). In this heterogeneous RD system, a variety of patterns including three-dimensional Turing patterns have been observed by computer tomography (see [Bánsági et al. (2011)] and references therein). Several control strategies have been developed for the purposeful manipulation of RD patterns. Below, we will differentiate between closed-loop or feedback control with and without nonlocal spatial coupling [Dahlem et al. (2008); Schneider et al. (2009); Siebert et al. (2014)] or time delay [Kim et al. (2001); Kyrychko et al. (2009)], and open-loop control that includes external spatio-temporal forcing, optimal control [Tröltzsch (2010)], control by imposed geometric constraints or heterogeneities, and others [Mikhailov and Showalter (2006); Schimansky-Geier et al. (2007); Vanag and Epstein (2008); Schöll and Schuster (2008)]. While feedback control relies on continuously running monitoring of the system's state, open-loop control is based on a detailed knowledge of the system's dynamics and its parameters. Feedback-mediated control has been applied quite successfully to the control of propagating one-dimensional (1D) waves as well as to spiral waves in 2D that are 1

Chemical Physics, 1984

The influence exerted on reaction processes by the coupling between the reaction coordinate x and transverse nonreactive modes is discussed. Attention is mainly focused on the synergism of inertia and multiplicative fluctuation, which enhances the reaction rate throughout a wide domain, ranging from the high to the low-friction region. The high-friction region is explored by applying the adiabatic elimination procedure

Physica E: Low-dimensional Systems and Nanostructures, 2014

Intersubband transitions in a multiple quantum well are studied in the presence of dc-ac fields. Band structure is obtained by using the finite difference method. Dynamics of system can be perfectly optimized by the selection of field parameters.

Physics Reports, 2006

We review experimental and theoretical studies on the design and control of spatiotemporal behavior in chemical systems. A wide range of approaches have been pursued to control spatiotemporal dynamics, from periodic forcing of medium excitability to imposing static and dynamic heterogeneities and geometric constraints on the medium to global feedback with and without delays. We focus on the design and control of spatiotemporal dynamics in excitable and oscillatory media. Experimental examples are taken from the Belousov-Zhabotinsky (BZ) reaction and the oxidation reaction of CO on single crystal Pt, which have become paradigmatic chemical systems for studies of spatiotemporal dynamics. We present theoretical characterizations of spatiotemporal dynamics and control based on the complex Ginzburg-Landau equation as well as models of the BZ and CO/Pt reactions. Controlling spatiotemporal dynamics allows the realization of specific modes of behavior or may give rise to completely new types of behavior.

Ferroelectrics, 1974

A molecular dynamics computation of S(q, w ) has been performed o n ii linear chain of harmonically coupled double wells. For order-disorder systems, a broad central peak and a low frequency peak appears on top of the usual bottom of thc well frequency of cvery q . For displacive systems an intense central peak distinct from the usual phonon peak appears at low 4.

We examine theoretically a new idea for spatial and temporal control of chemical reactions. When chemical reactions take place in a mixture of solvents, an external electric field can alter the local mixture composition, thereby accelerating or decelerating the rate of reaction. The spatial distribution of electric field strength can be non-trivial and depends on the arrangement of the electrodes producing it. In the absence of electric field, the mixture is homogeneous and the reaction takes place uniformly in the reactor volume. When an electric field is applied, the solvents separate and the reactants are concentrated in the same phase or separate to different phases, depending on their relative miscibility in the solvents, and this can have a large effect on the kinetics of the reaction. This method could provide an alternative way to control runaway reactions and to increase the reaction rate without using catalysts. Published by AIP Publishing. [http://dx.doi.org/10.1063/1.4951709]

2023

Investigating the intricacies of confined nonlinear dynamics presents formidable challenges, primarily due to the unpredictable behaviour of molecular constituents. This study introduces a promising avenue for comprehending and harnessing nonlinear dynamics within constrained domains, with broad applications spanning fields like nanofluidics and astrophysics. Quantum-level control emerges as a powerful tool, enabling the manipulation of classical systems to achieve specific outcomes, including quantum control of fluidic behaviour at the nanoscale for application in actuation in nanofluidics. Of particular significance is the observation of an asymptotic function that describes soliton behaviour within a transformed mathematical framework, shedding light on the practical implications of abstract representations. Solitons, known to vanish mathematically, exhibit intriguing transformations over time, influenced by phase gradients. Soliton formations, tracked from 1 ns to 83 ns, reveal dynamic transformations, evolving from their initial state with intriguing variations in amplitude and phase angle. These solitons, under the influence of subtle phase gradients, transition towards states characterised by reduced amplitude and expanded spatial extent. The ability to exercise quantum control over nanoscale fluidic behaviours beckons novel applications, notably in nanofluidic actuation. These findings hold the potential to revolutionise the efficiency of quantum computing in addressing nonlinear differential equations, offering new opportunities for precision-driven progress across scientific disciplines.

Chemical Society Reviews, 2002

Chemical reactions are at the heart of chemistry and the dream of controlling the outcome of these reactions is an old one. Thus, with given reactants, a solvent and perhaps assisted by a catalyst, we would like to 'steer' the reactants into a particular desired product. This review focuses on how to control the dynamics of chemical reactions, beyond traditional temperature control, with the emphasis on unimolecular reactions. The electromagnetic radiation of lasers can induce so-called coherent dynamics. The recent theoretical and experimental results on this coherent control are explained and illustrated with computational and experimental examples.

Physical Review A (Atomic, Molecular, and Optical Physics), 2014

2024

Investigating nonlinear fluid dynamics remains a challenge across physics from nanofluidics and biophysics to astrophysics. Here we introduce a quantum/classical theoretical approach that takes into account both quantum correlations and classical behaviour within a 2D fluid that is confined in a 3 µm side square. We employ a modified Gross-Pitaevskii equation, encompassing many-body interactions and confinement. This system reveals complex fluid dynamics characterised by dissipative solitons; a significant outcome is an asymptotic function that describes the soliton behaviour. The solitons exhibit intriguing geometrical and temporal transformations, guided by subtle phase gradients. We trace the soliton evolution from 1 ns to 83 ns, revealing the emergence of geometric oscillations in amplitude and phase angles. Under these phase gradients, solitons transition to states with reduced amplitude and expanded spatial profiles. These results show that geometric solitons can emerge from a quantum noisy environment, and lead us to propose an interesting possibility: it is feasible to control and manipulate nonlinear dynamics in systems with finite-range interactions and confinement using quantum control. By bridging quantum and classical dynamics, this study links various scientific disciplines, including non-equilibrium phases of condensed matter, unconventional/quantum computing and advanced control of nanofluidics. From a more fundamental perspective, this possibility of quantum control of classical behaviour advances our understanding of physics within multidimensional Hilbert spaces.

Physics Letters A, 1995

We perform Langevin dynamic numerical simulation on a double-well potential system subjected to an asymmetric saw-tooth type external time varying field and white noise forces. The hysteresis loss calculated from the first-passage time distribution obtained shows asymmetric behaviour with respect to the asymmetry in the field sweep. The hysteresis loss, in our model, being a measure of the synchronized passages from one well to the other, indicates asymmetric "correlated" passages in the two opposing directions when driven by a temporally asymmetric external field in the presence of white noise (fluctuating) forces. The implication of our results on the phenomena of predominantly unidirectional motion of a Brownian particle in a symmetric periodic (nonratchet-like) potential is discussed.

The Journal of Chemical Physics, 2001

Over the past three years we have made significant contributions to the ongoing development of the coherent control of atomic and molecular processes. Specifically, we have contributed to (1) bimolecular reaction dynamics and controlled collision phenomena; control of molecular chirality and asymmetric synthesis; (3) theory, and practical considerations, in the control of the photodissociation of real systems; (4) control in large molecular systems; (5) the continued development of semiclassical mechanics specifically for coherent control applications; and (6) control of molecular nanoscale deposition on surfaces.