Maxwell Displacement Current Research Articles

Molecular switching in single azobenzene monolayers

The molecular switching between cis-form and trans-form in azobenzene monolayers was investigated by means of the Maxwell-displacement-current (MDC)-measuring technique developed by the authors. The MDC current pulses were generated across azobenzene monolayers by the cis-trans photoisomerization, and the direction of the MDC depended on the molecular area as the result of the change in the vertical component of dipole moment of the monolayers due to the cis-trans photoisomerization. We concluded that the MDC technique is very helpful for the detection of molecule switching in monolayer films.

The Calculation of Biaxial Molecules at the Air-Liquid Interface

The molecular orientational order and the Maxwell displacement current (MDC) of biaxial molecules are calculated with a thermostatistical approach in the range of molecular area of immeasurably low surface pressure.

Calculation of Molecular Orientational Order and Maxwell Displacement Current of Biaxial Molecules at the Air-liquid Interface

On the basis of the electrodynamic interaction of biaxial molecules (with their larger permanent dipoles perpendicular to the molecular axes) with a liquid surface, we calculate the molecular orientational order and the Maxwell displacement current (MDC) of biaxial molecules with a thermostatistical approach in the range of molecular area of immeasurably low surface pressure. It is shown that MDC generated by orientational change of the permanent dipoles along long molecular axes dominates the compression process shortly after the onset of the transition at A0 from the planar surface alignment phase to the polar one, despite their smaller dipole moments than those perpendicular to the long molecular axes. This agrees with the fact that the MDC should change with the dipole moment along the long molecular axis. The results also reveal the thermodynamic motions of the dipoles parallel and perpendicular to the long molecular axis during the compression process.

Convection Displacement Current and Generalized Form of Maxwell–Lorentz Equations

Some mathematical inconsistencies in the conventional form of Maxwell's equations extended by Lorentz for a single charge system are discussed. To surmount these in the framework of Maxwellian theory, a novel convection displacement current is considered as additional and complementary to the famous Maxwell displacement current. It is shown that this form of the Maxwell–Lorentz equations is similar to that proposed by Hertz for electrodynamics of bodies in motion. Original Maxwell's equations can be considered as a valid approximation for a continuous and closed (or going to infinity) conduction current. It is also proved that our novel form of the Maxwell–Lorentz equations is relativistically invariant. In particular, a relativistically invariant gauge for quasistatic fields has been found to replace the non-invariant Coulomb gauge. The new gauge condition contains the famous relationship between electric and magnetic potentials for one uniformly moving charge that is usually attributed to the Lorentz transformations. Thus, for the first time, using the convection displacement current, a physical interpretation is given to the relationship between the components of the four-vector of quasistatic potentials. A rigorous application of the new gauge transformation with the Lorentz gauge transforms the basic field equations into a pair of differential equations responsible for longitudinal and transverse fields, respectively. The longitudinal components can be interpreted exclusively from the standpoint of the instantaneous "action at a distance" concept and leads to necessary conceptual revision of the conventional Faraday–Maxwell field. The concept of electrodynamics dualism is proposed for self-consistent classical electrodynamics. It implies simultaneous coexistence of instantaneous long-range (longitudinal) and Faraday–Maxwell short-range (transverse) interactions that resembles in this aspect the basic idea of Helmholtz's electrodynamics.

Maxwell displacement current due to phase transitions in liquid crystals on a water surface

The phase transitions of Langmuir films of the liquid crystals (LCs) 4′-n-pentyl-4-cyano-biphenyl (5CB), 4′-n-octyl-4-cyano-biphenyl (7CB), 4′-n-octyl-4-cyano-biphcnyl (8CB) and 4′-n-decyi-4-cyano-biphenyl (10CB), have been investigated by a Maxwell displacement current (MDC) measuring technique, A phase transition of LC molecules from the planar surface alignment phase to the polar one was clearly detected in the range of low surface pressures during monolayer compression. A phase transition between a stable monolayer phase and a stable three-layer phase of the liquid crystal film was detected during further monolayer compression.

Analysis of dielectric relaxation phenomena with molecular orientational ordering in monolayers at the liquid-air interface.

Starting from the Debye theory of rotational Brownian motion, we analyzed the dielectric relaxation phenomena with molecular orientational ordering in Langm\uir film on a water surface, assuming that the orientational distribution of the constituent rodlike polar molecules is ruled by Boltzmann statistics. The transient behavior of the polar molecules induced by the application of step compression at the molecular area $A={A}_{i}(l{A}_{c})$ is discussed with taking account of the friction constant of monolayer $\ensuremath{\xi}$, and the dielectric relaxation time $\ensuremath{\tau}$. Here ${A}_{c}$ is the critical molecular area defined as $\ensuremath{\pi}{l}^{2}$ ($l$: the length of rodlike polar molecule). The orientational order parameter $S$ of monolayers and Maxwell displacement current (MDC) at the dielectric relaxation process were obtained, for the first time, with the consideration of $\ensuremath{\xi}$ and $\ensuremath{\tau}$. On the basis of the analysis developed here, we examined the generation of MDC across 4-cyano-4\ensuremath{'}-5-alkyl-biphenyl (5CB) Langm\uir film by monolayer compression.

Photoregulation of Liquid Crystal Alignment Using Azobenzene Monolayers and Generation of Maxwell Displacement Current

The Maxwell displacement current (MDC) measurement technique has been applied to the investigation of monolayers of poly(vinyl alcohol)s bearing azobenzene side chains (6Az5PVA) mixed with p-pentyl-p'-cyano-biphenyl (5CB) on a water surface. For mixed monolayers containing trans-form 6Az5PVA and 5CB, MDC was not generated by alternating photoirradiation of UV and visible light. In contrast, for mixed monolayers containing cis-form 6Az5PVA and 5CB, MDC was generated due to photoisomerization. It was concluded that the 6Az5PVA monolayers deposited in cis-form can photoregulate the alignment of 5CB molecules.

Maxwell displacement current across azobenzene polyimide multilayers caused by photoirradiation

The Maxwell displacement current (MDC) measuring technique has been applied for the investigation of azobenzene polyimide multilayer films under alternating photoirradiation with visible and ultraviolet (UV) light. MDCs flow across multilayer films due to the photoisomerization of the azobenzene polyimide molecules caused by alternating irradiation with UV and visible light. MDCs are also generated due to the photoexcited electron transfer in multilayer films. Finally, it is found that MDCs caused by the photoisomerization are suppressed after the deposition of polyamic acid onto the azobenzene films.

Photoinduced Maxwell-Displacement-Current Acr-Oss Polyamic Acid and Azobenzen Langmuir-Blodgett Films

Abstract Maxwell-displacement-current (MDC) measuring technique has been applied to the investigation of polyamic acid and azobenzen Langmuir-Blodgett films by alternating photoirradiation with visible light and ultraviolet light. MDCs across multilayer films were generated alternatingly due to the cis-trans photoisomerization of AZBPAA films. It was also found that the photoexcited electron transfer also made a contribution to the generation of MDCs with ultraviolet irradiation. Finally, MDCs across AZBPAA monolayers were found to be suppressed as a result of the deposition of PAA layers onto the AZBPAA monolayers, possibly due to the inhibitation in the cis-trans photoisomerization.

Maxwell Displacement Current across Phospholipid Monolayers at the Air/Water Interface

The organization of phospholipid monolayers on a water surface was investigated by means of the Maxwell displacement current (MDC) measurement technique. The phase transition from the gaseous phase to the gaseous-fluid phase which accompanies the polar ordering of lipid molecules was detected by the technique in the range of immeasurably low surface pressure, and the molecular area which gives the onset of the transition was determined for various lipid monolayers. The vertical component of the dipole moment of lipid membranes was determined from the charge flowing through the circuit, and it was also determined by a curve-fitting method from the MDC generated in the fluid phase.

Detection of phase transitions in liquid crystals on a water surface by a Maxwell displacement current-measuring technique

The phase transitions of Langmuir films of liquid-crystal 4-cyano-4′-5-alkyl-biphenyl (5CB), 4-cyano-4′-7-alkyl-biphenyl (7CB), 4-cyano-4′-8-alkyl-biphenyl (8CB), and 4-cyano-4′-10- alkyl-biphenyl (10CB) were investigated by a Maxwell displacement current (MDC)-measuring technique. A weak first-order phase transition of the orientation of LC molecules from the isotropic phase to the polar one was clearly detected by compressing the film in the range of immeasurably low surface pressure by means of the technique. For further compression, a first-order phase transition between a stable monolayer phase and a stable three-layer phase of the liquid crystal film was detected. The result shows that the MDC-measuring technique is useful in the detection of phase transitions over the entire range of molecule areas.

Measurement of the orientational change of N-Docosylquinolium-TCNQ monolayers using Maxwell-displacement-current

Maxwell-displacement-current(MDC) measuring technique has been applied to the study of single monolayers of N-Docosylquinolium-TCNQ. The MDC was generated from single monolayers on a water surface by monolayer compression. The MDC was also generated from single monolayers on solid substrates with thermal stimulation. The orientational change of molecules in single monolayers was discussed on the basis of the MDCs obtained.

Presence of In-Plane Orientation in Single Azobenzene Monolayers by Maxwell-Displacement-Current Measurement

The presence of in-plane orientation of azobenzene molecules in single monolayers of polymer films was detected by means of Maxwell-displacement-current (MDC) measurement with linearly polarized photoirradiation. The magnitude of MDC generated by photoirradiation polarized in a direction parallel to the dipping direction of the azobenzene monolayer was greater than that generated by photoirradiation normal to the dipping direction. The in-plane orientational change in azobenzene molecules in single polymeric monolayers was produced as a result of alternating polarized photoirradiation of UV and visible light for a sufficiently long time, and it was also detected by means of MDC measurement.

Maxwell displacement current across single monolayers

An electrical technique that allows reorganization of single monolayers to be probed by measuring the Maxwell displacement current flowing across monolayers is described. The Maxwell displacement current is generated from single monolayers with the application of an external stimulus ( e.g. pressure, light or heat) in the absence of an external electric field. The current across octadecylamine monolayers with thermal stimulation is given as an example of the Maxwell displacement currents.

Displacement current generation across single monolayers of polyamic acids having pendant groups at the air-water interface

We investigated the reorganization of three kinds of monolayer polyamic acids, having different pendant groups (denoted PAA, AzOME and AzNO 2), on a water surface with measurements of the surface pressure-area (π− A) isotherms and the Maxwell displacement current. The three kinds of monolayers traced a similar π− A isotherm, indicating a similar conformational change on the water surface. For all three kinds of monolayer, some displacement current peak was generated during monolayer compression in the range before the initial rise of the surface pressure. The magnitude of the peak depended on the dipole moment of the pendant group ends incorporated in the polyamic acid monolayers. It was concluded that the current generation is due to the condensation of pendant group ends which stand up on the water subphase, and to monolayer compression.

Universal low-temperature ac conductivity of macroscopically disordered nonmetals.

This paper discusses a macroscopic model for ac conduction in electronically or ionically conducting disordered solids. The model considers ac conduction in an inhomogeneous solid that is characterized by a spatially randomly varying thermally activated (frequency-independent) conductivity. Discretizing Maxwell's equations leads to an equivalent electrical circuit that is a simple-cubic lattice where each pair of nodes are linked by a resistor and a capacitor in parallel. The values of the resistors are determined by the local resistivity while the capacitors are all equal, given by the infinite-frequency dielectric constant. It is shown that the capacitor currents are Maxwell's displacement currents. Assuming uncorrelated resistances, the model is solved analytically at low temperatures in the effective-medium approximation (EMA) and in a naive percolation-path approximation. Both approximations predict similar universal ac responses as T\ensuremath{\rightarrow}0, where the macroscopic frequency-dependent conductivity becomes independent of the activation-energy probability distribution. The universality represents an unusual type of regularity appearing in the extreme disorder limit. The universality prediction is tested by computer simulations of 200\ifmmode\times\else\texttimes\fi{}200 lattices in two dimensions and of 50\ifmmode\times\else\texttimes\fi{}50\ifmmode\times\else\texttimes\fi{}50 lattices in three dimensions. The computer simulations show that the EMA works very well in two dimensions in the whole temperature range studied; in particular, the low-temperature universality prediction is confirmed. In three dimensions the universality prediction is confirmed as well.

Maxwell displacement-current generation due to trans-cis photoisomerization in monolayer Langmuir–Blodgett film

The Maxwell displacement current was generated from 4-octyl-4′-(5-carboxylpentamethyleneoxy)-azobenzene (denoted as 8A5H) monolayer Langmuir–Blodgett films prepared on SnO2-coated glass substrates due to trans-cis photoisomerization of 8A5H by application of alternate irradiation with UV light and visible light. The generation of the displacement current by the photoirradiation was examined in connection with the degree of H-aggregate of 8A5H molecules. It was concluded that the high-H-aggregate molecule of the azobenzene group is not appropriate for the application of the molecular switching based on the displacement-current measurement.

Generation of the displacement current by the transformation of J-aggregates in spreading monolayers of squarylium dye

Maxwell displacement currents generated from monolayers of squarylium dye with propyl groups (SQ) and from mixed monolayers with arachidic acid were investigated during the course of monolayer compression in connection with the formation of J-aggregates in the monolayers. Abrupt changes in the generation of displacement current were observed for monolayers of SQ due to the transformation between two types of J-aggregates with different absorption spectra. In contrast, for mixed monolayers with arachidic acid which show no transition of J-aggregates, abrupt changes in the displacement current were not observed. It was concluded that displacement current measurement is effective in the detection of the transformation of the molecular arrangement in aggregates.

The Analysis of a Model for Wave Motion in a Liquid Semiconductor: Boundary Interaction and Variable Conductivity

The theory of conducting fluids in relative motion with small conductivity is studied with a model including the Maxwell displacement current. The model is linearized, and the interaction of waves with a plane boundary in three space is studied for two orientations of the external magnetic field. It is found that two families of boundary conditions preserve energy in one orientation (external field orthogonal to the boundary), while in the other (external field parallel to the boundary) only one condition exists which preserves energy. It is shown that generalized Fourier transforms exist, generated from the generalized eigenfunction expansions. Further, it is shown that surface waves are not supported by this model, indicating that their presence is unstable when relative motion of the fluid is allowed (surface waves exist in the still fluid case). Finally, the problem of variable conductivity (decaying to zero at infinity) is studied and steady-state and time dependent solutions are shown to exist for c...

Measuring the unmeasurable

After more than a century, the reality of Maxwell's displacement current has been demonstrated by direct measurement. So, too, but less conclusively, has been the Aharonov/Bohm effect.