Abstract:
We investigate photodetachment from negative ions in a homogeneous 1.0-T magnetic field and a parallel electric field of approximately 10 V/cm. A theoretical model for detachment in combined fields is presented. Calculations show that a field of 10 V/cm or more should considerably diminish the Landau structure in the detachment cross section. The ions are produced and stored in a Penning ion trap and illuminated by a single-mode dye laser. We present preliminary results for detachment from S- showing qualitative agreement with the model. Future directions of the work are also discussed.

Abstract:
The photodetachment cross section of H^- in parallel electric and magnetic fields near an elastic surface is derived and calculated by using the closed orbit theory. It is found that the elastic surface can produce some interesting effects. Besides the closed orbits previously found by Peters et al. for the H^- in parallel electric and magnetic fields, some additional closed orbits are produced due to the effect of the elastic surface. The results show that the cross section oscillation is much more complicated in comparison with the cross section of H^- in parallel external fields without surface. Each peak in the Fourier transformed cross section corresponds to the period of one detached electron closed orbit. This study provides a new understanding of the photodetachment of negative ions in the presence of external fields and surface.

Abstract:
Image fields generated by a bunch of charged particles between two parallel perfectly conducting plates are studied in detail. We derive exact analytical expressions for external fields of a charged relativistic bunch with a circular cross-section. Summation of image fields by the direct method invented by Laslett allows the infinite series to be represented in terms of elementary trigonometric functions. 1. Introduction In an accelerator, the charged beam is influenced by an environment (a beam pipe, accelerator gaps, magnets, collimators, etc.), and a high-intensity bunch induces surface charges or currents into this environment. This modifies the electric and magnetic fields around the bunch. There is a relatively simple method to account for the effect of the environment by introducing image charges and currents. Methods of image fields summation are described in the paper [1], which presents some field coefficients calculated for infinite parallel-plate vacuum chambers, magnetic poles, and vacuum chambers with elliptical cross-sections and variable aspect rations. The resulting image field was calculated only in the linear approximation and depends linearly on the deviations and of the bunch center and the position of a test particle, respectively, from the axis. The approximation used is incorrect if the field observation point is located far from the bunch or if the bunch center is close to a conducting wall. In the present paper we consider the classical problem of the image field summation once again for a very simple geometry, namely, a relativistic bunch moving between infinitely wide parallel perfectly conducting planes. The problem is far from being a pure academic one [2, 3]. In applications, in particular by study of the electron cloud effect [4] and the dynamics of photoelectrons in the beam transport system, it is important to know the distribution of electromagnetic fields not only in vicinity of the bunch but also in the whole collimator gap. In free space, the external radial electric and azimuthal magnetic self-fields of a cylindrical bunch with a uniform charge density are described by [5–7] where , is the linear charge density, the normalized velocity of the beam constituents, and the velocity of light. We did not find publications with attempts to sum up the series (3) in an approximation beyond the linear one. In the following sections we present the exact solutions of the problem. 2. Electric Field from Image Charges Following Laslett [1] (see also [5]), we consider a relativistic bunch of the length between infinitely wide

Abstract:
Laser-atom interaction can be an efficient mechanism for the production of coherent electrons. We analyze the dynamics of monoenergetic electrons in the presence of uniform, perpendicular magnetic and electric fields. The Green function technique is used to derive analytic results for the field--induced quantum mechanical drift motion of i) single electrons and ii) a dilute Fermi gas of electrons. The method yields the drift current and, at the same time it allows us to quantitatively establish the broadening of the (magnetic) Landau levels due to the electric field: Level number k is split into k+1 sublevels that render the $k$th oscillator eigenstate in energy space. Adjacent Landau levels will overlap if the electric field exceeds a critical strength. Our observations are relevant for quantum Hall configurations whenever electric field effects should be taken into account.

Abstract:
Large parallel ($\leq$ 100 mV/m) and perpendicular ($\leq$ 600 mV/m) electric fields were measured in the Earth's bow shock by the vector electric field experiment on the Polar satellite. These are the first reported direct measurements of parallel electric fields in a collisionless shock. These fields exist on spatial scales comparable to or less than the electron skin depth (a few kilometers) and correspond to magnetic field-aligned potentials of tens of volts and perpendicular potentials up to a kilovolt. The perpendicular fields are amongst the largest ever measured in space, with energy densities of $\epsilon_0 E^2/ n k_b T_e$ of order 10%. The measured parallel electric field implies that the electrons can be demagnetized, which may result in stochastic (rather than coherent) electron heating.

Abstract:
Statistics of tunneling rates in the presence of chaotic classical dynamics is discussed on a realistic example: a hydrogen atom placed in parallel uniform static electric and magnetic fields, where tunneling is followed by ionization along the fields direction. Depending on the magnetic quantum number, one may observe either a standard Porter-Thomas distribution of tunneling rates or, for strong scarring by a periodic orbit parallel to the external fields, strong deviations from it. For the latter case, a simple model based on random matrix theory gives the correct distribution.

Abstract:
Multi-electron giant dipole resonances of atoms in crossed electric and magnetic fields are investigated. Stationary configurations corresponding to a highly symmetric arrangement of the electrons on a decentered circle are derived, and a normal-mode and stability analysis are performed. A classification of the various modes, which are dominated by the magnetic field or the Coulomb interactions, is provided. Based on the MCTDH approach, we carry out a six-dimensional wave-packet dynamical study for the two-electron resonances, yielding in particular lifetimes of more than 0.1 $\mu$s for strong electric fields.

Abstract:
A system of two quantum wells (QW), one made of HgCdTe and the other of HgCdMnTe, subjected to electric and magnetic fields $F$ and $B$ parallel to the growth direction, is proposed and described theoretically. It is shown that in such a system the spin $g$ factor of mobile electrons strongly depends on the sign and magnitude of electric field. Adjusting $F$ at a constant $B$ one can transfer almost all electrons into one or the other QW and polarize their spins along the desired orientation. Changing $B$ at a constant $F$ can produce a similar transfer and polarization effect. Possible applications of the spatial reservoirs filled with spin-polarized electrons are discussed.

Abstract:
By using a semiclassical method, we present theoretical computations of the ionization rate of Rydberg lithium atoms in parallel electric and magnetic fields with different scaled energies above the classical saddle point. The yielded irregular pulse trains of the escape electrons are recorded as a function of emission time, which allows for relating themselves to the terms of the recurrence periods of the photoabsorption. This fact turns to illustrate the dynamic mechanism how the electron pulses are stochastically generated. Comparing our computations with previous investigation results, we can deduce that the complicated chaos under consideration here consists of two kinds of self-similar fractal structures which correspond to the contributions of the applied magnetic field and the core scattering events. Furthermore, the effect of the magnetic field plays a major role in the profile of the autoionization rate curves, while the contribution of the core scattering is critical for specifying the positions of the pulse peaks.

Abstract:
We present a new method for computing the recurrence spectra of n≈40, m=0 lithium Rydberg atoms in strong parallel external electric and magnetic fields. This method is based on an extended closed-orbit theory allowing the computation of the scattering of the electron by the ionic core. We pay particular attention to the scaling properties, which are extremely important for understanding the correspondence between classical and quantum mechanics. The spectra with a constant scaled electric field \tilde F=0.01 and a scaled energy ε=-0.03 are recorded and compared with those of hydrogen obtained by the standard closed-orbit theory. The result shows that the additional strong resonance structures can be interpreted in terms of the core-scattered classical closed orbits.