Formation of conic cusps at the surface of liquid metal in electric field

The formation dynamics is studied for a singular profile of a surface of an ideal conducting fluid in an electric field. Self-similar solutions of electrohydrodynamic equations describing the fundamental process of formation of surface conic cusps with angles close to the Taylor cone angle 98.6° are obtained. The behavior of physical quantities (field strength, fluid velocity, surface curvature) near the singularity is established.     

Formation of root singularities on the free surface of a conducting fluid in an electric field

The formation of singularities on a free surface of a conducting ideal fluid in a strong electric field is considered. It is found that the nonlinear equations of two-dimensional fluid motion can be solved in the small-angle approximation. This enables us to show that for almost arbitrary initial conditions the surface curvature becomes infinite in a finite time.     

The effect of strong electric field on lattice relaxation at metal surface

The density functional formalism is used to study changes in the lattice relaxation induced by negative electric field at closed packed faces of Li, Na, Al and Cu. Due to the simple form of the parametrized density profile assumed, the calculation is performed analytically. For the typical fields applied in field emission the calculated relaxations can be increased up to 21% due to the electric field, depending on metal and crystallographic plane considered.     

Phase transformations of a condensate on a crystal surface in a strong electric field

The evolution of the phase state of the water vapor condensate of the silver iodide crystal surface in an applied electric field up to 10 V/nm is studied by computer simulation. The previously found domain structure of the contact layer is stable against the external field and remains up to the complete break of the molecular film. In a strong electric field, the film condensation mode is changed by the formation of a new phase consisting of molecular nanothreads growing in the direction of the electric field lines. The transition to the new state is sharp. The presence of a phase transition is likely analogous to that accompanying the transformation of water microdrops to the superpolarized state under the action of an external electric field at stratospheric temperatures.     

Influence of a strong electric field on the decay of autoionizing states formed when multiply charged ions approach a metal surface

Upon collisions of multiply charged ions with a surface, the electric field of the image charge causes Stark splitting of the ion levels; in this case, the Stark states whose energy approaches the electron binding energy in the metal with a decrease in the distance to the surface are selectively occupied. It is shown that consideration of the electric field effect leads to an increase in the probability of Auger transitions in the presence of field. This effect changes our representations about the scheme of occupation of lower levels of multiply charged ions.     

Equilibrium configurations of the conducting liquid surface in a nonuniform electric field

Possible equilibrium configurations of the free surface of a conducting liquid deformed by a nonuniform external electric field are investigated. The liquid rests on an electrode that has the shape of a dihedral angle formed by two intersecting equipotential half-planes (conducting wedge). It is assumed that the problem has plane symmetry: the surface is invariant under shift along the edge of the dihedral angle. A one-parametric family of exact solutions for the shape of the surface is found in which the opening angle of the region above the wedge serves as a parameter. The solutions are valid when the pressure difference between the inside and outside of the liquid is zero. For an arbitrary pressure difference, approximate solutions to the problem are constructed and it is demonstrated the approximation error is small. It is found that, when the potential difference exceeds a certain threshold value, equilibrium solutions are absent. In this case, the region occupied by the liquid disintegrates, the disintegration scenario depending on the opening angle.     

Formation of electric discharges above the free surface of a current-carrying liquid

The study is devoted to analysis of the formation of high-current electric discharges developing above the free surface of a liquid metal, deformed as a result of the interaction of the electric current passing through the liquid metal with the intrinsic magnetic field. We report on the electric characteristics of discharges and parameters of their initiation, consider the patterns of deformation of the free surface and the formation of electric discharges, describe the processes occurring in the system, and discuss the mechanism of cyclic formation of discharges above the liquid metal surface.     

Polaron in a strong alternating electric field

The solution is found for the transport equation for a Feynman polaron having arbitrary coupling interacting with the acoustic oscillations in an alternating electric field. In the low-frequency case, this solution cannot be normalized — there are runaway polarons. For high frequencies, this effect is absent. Equations are obtained for the electrical conductivity of polaron semiconductors for various particular cases, including the runaway regime.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 45–49, April, 1979.     

Dynamics of the free surface of a conducting liquid in a near-critical electric field

Near-critical behavior of the free surface of a perfectly conducting liquid in an external electric field is considered. Based on an analysis of three-wave processes using the method of integral estimates, sufficient criteria for hard instability of a planar surface are formulated. It is shown that the higher-order nonlinearities do not saturate the instability, for which reason the growth of disturbances has an explosive character.     

The influence of electric of H- near field on the photodetachment a metal surface

The influence of electric field on the photodetachment of H- near a metal surface is investigated based on the closed-orbit theory. It is found that the photodetachment of H- near a metal surface is not only related to the electric field strength but also to the electric field direction. If the electric field is along the ＋z axis, it can strengthen the oscillation in the photodetachment cross section. However, if the electric field is along the -z axis, since the direction of electric field force is opposite to that of static-image force caused by the metal surface, the situation becomes much more complicated. When the electric field is very weak, its influence can be neglected. The photodetachment cross section is nearly the same as that when a single metal surface exists. When the electric field strength is strong enough, the electric field force is able to counteract the metallic attraction, therefore no closed orbit is formed. If the electric field continues to increase until its influence becomes dominant, the photodetachment cross section approaches the case of the photodetachment of H^- in an electric field. Our results may be useful for guiding future experimental studies on the photodetachment of negative ions near surfaces.     

Effects of an intense electric field on metal surface geometry

The effects of a strong positive electric field on the surface geometry of a single crystal, smooth metal surface are discussed. Explicit density functional calculations are presented for the field induced relaxation and evaporation of the Al(111) surface layer of atoms. The results are then explained in terms of a simple model and approximately extended to other metal surfaces. Our model determines the critical field for surface evaporation if there is no reconstruction. Finally, we will briefly mention the possibility of field induced reconstruction and its role in determining the critical field for stripping the surface layer of atoms.     

Photodetachment of negative ion in a gradient electric field near a metal surface

Based on closed-orbit theory, the photodetachment of H in a gradient electric field near a metal surface is studied. It is demonstrated that the gradient electric field has a significant influence on the photodetachment of negative ions near a metal surface. With the increase of the gradient of the electric field, the oscillation in the photodetachment cross section becomes strengthened. Besides, in contrast to the photodetachment of H near a metal surface in a uniform electric field, the oscillating amplitude and the oscillating region in the cross section of a gradient electric field also become enlarged. Therefore, we can use the gradient electric field to control the photodetachment of negative ions near a metal surface. We hope that our results will be useful for understanding the photodetachment of negative ions in the vicinity of surfaces, cavities, and ion traps.     

氢负离子在均匀电场和金属面附近的光剥离研究

利用闭合轨道理论,计算了氢负离子在均匀电场和金属面附近的光剥离截面.结果表明,在均匀电场的基础上加上金属面之后,在电离阈附近氢负离子的光剥离截面发生了很大的变化,和仅有均匀电场存在时的光剥离截面相比,截面的振荡幅度增大,振荡频率减小.并且在电场强度相同时,随着金属面与氢负离子距离的不断增大,光剥离截面振荡的幅度不断减小,振荡的频率不断增大,当金属面和氢负离子的距离增大到一定值时,金属面的影响消失,氢负离子的光剥离截面趋近于只有电场存在时的情况.这一结果对于研究负离子体系在界面附近的光剥离问题具有一定的参考价值.     

Photodetachment microscopy of the hydrogen negative ion in electric field near a metal surface

According to the semi-classical theory, we study the photodetachment microscopy of H^- in the electric field near a metal surface. During the photodetachment, the electron is photo-detached by a laser and the electron is drawn toward a position-sensitive detector. The electron flux distribution is measured as a function of position. Two classical paths lead the ion to any point in the classically allowed region on the detector, and waves traveling along these paths produce an interference pattern. If the metal surface perpendicular to the electric field is added, we find that the interference pattern is related not only to the electron energy and the electric-field strength, but also to the ion--surface distance. Besides, the laser polarization also has a great influence on the electron flux distribution. We present calculations predicting the interference pattern that may be seen in experiment. We hope that our study can provide a new understanding of the electron flux distribution of negative ions in external field and surface, and can guide the future experimental research on the negative ion photo-detachment microscopy.     

Effect of surface electric field on the anchoring of nematic liquid crystals

We analyse the influence of adsorbed ions and the resulting surface electric field and its gradient on the anchoring properties of nematics with ionic conductivity. We take into account two physical mechanisms for the coupling of the nematic director with the surface electric field: (i) the dielectric anisotropy and (ii) the coupling of the quadrupolar component of the flexoelectric coefficient with the field gradient. It is shown that for sufficiently large fields near saturated coverage of the adsorbed ions, there can be a spontaneous curvature distortion in the cell even when the anchoring energy is infinitely strong. We also discuss the director distortion when the anchoring energy of the surface is finite. Received: 29 September 1997 / Received in final from: 10 November 1997 / Accepted: 18 November 1997     

强电场下气泡形变对液体绝缘的影响

基于液体气泡击穿的椭球模型,推导了气泡形变的流体动力学方程;利用软件Comsol模拟了气泡受力后的形变;根据模拟结果,结合气体击穿的帕邢定律,讨论了气泡形变对液体绝缘的影响。结果表明:气泡在静电引力和表面张力的作用下,沿电场线方向拉伸成椭球,椭球长短轴之比与外加电场强度和气泡初始半径成正比;形变导致电场方向气体通道延长,气泡更容易击穿,外加气压是避免气泡击穿的有效途径之一,外加气压的大小与电场强度和气泡初始半径成正比。     

Effect of an electric field on the surface tension of a liquid at low temperatures

An external electric field changes the dispersion law of waves on the surface of a liquid. Besides the usual capillary term (∝k ³, k is the wave number) and gravitational term (∝k), a term quadratic in the wave vector appears in the expression for the square of the frequency in a homogeneous field. These excitations are associated with the variation of the coefficient of surface tension of the liquid at low temperatures. In the case of a large field tangent to the surface, the correction is proportional to T ^8/3, unlike the T ^7/3 correction in the absence of a field. Zh. éksp. Teor. Fiz. 111, 1369–1372 (April 1997)     

Temperature dependence of the surface electric field gradient for indium metal

The electric field gradient at indium surfaces was studied with¹¹¹In PAC-probes as a function of temperature. The surface field gradient was determined to be temperature independent up to 100 K and the fraction of¹¹¹In surface sites shows a pronounced annealing behaviour between 150 K and 250 K.