Kinematic dipole model for the anisotropy of quasimolecular X-rays

For the angular dependence of quasimolecular X-ray emission in heavy ion colliding systems we present a semiclassical adiabatic model taking into account spontaneous dipole radiation. Using the most characteristic levels from a DFS-correlation diagram we are able to explain the behaviour of the observed anisotropy.     

Nuclear acoustic resonance in copper via coupling to the magnetic dipole moment

A nuclear acoustic resonance signal has been observed in copper. The absolute intensity, line shape ahd angular dependence are explained by the coupling via the dipole magnetic moments.     

Experimentally observed orientation of C60F18 molecules on the nickel single crystal (100) surface

The angular dependence of near edge X-ray absorption fine structure (NEXAFS) spectra has been obtained in the vicinity of carbon and fluorine 1s absorption edges in a monolayer film of polar fullerene fluoride (C₆₀F₁₈) molecules on a Ni(100) substrate. The fine structure of the spectra has been identified according to experimental data via calculations based on the density functional theory, and the angular dependence of the spectra has been explained. The orientations of structural molecular fragments are determined from the angular dependence of the NEXAFS spectra. It is demonstrated that the electric dipole moment of a C₆₀F₁₈ molecule is oriented along the normal to the substrate surface with an accuracy of 5°.     

Inelastic scattering of electrons from inert gas atoms in the eikonal distorted-wave approximation

The excitation of dipole states in neon and argon by electron impact has been calculated in the eikonal distorted-wave approximation. The total and differential cross-sections, the angular distributions of electrons and photons are in good agreement with experiment.     

l-changing electron impact cross sections for high Rydberg atoms with application to helium experiments

The impact parameter method is applied to high Rydberg atoms for estimating Δn=0 dipole transition cross sections. Values for high-l states are determined in large part by polarization and relativistic fine-structure contributions to energy levels. Computed cross sections for low-l helium atoms show good agreement with angular momentum transfer cross sections from electron impact experiments over the range 20<n<80.     

Testing spatial noncommutativity via Rydberg atoms

The possibility of testing spatial noncommutativity via Rydberg atoms is explored. An atomic di-pole of a cold Rydberg atom is arranged in appropriate electric and magnetic fields, so that the motion of the dipole is constrained to be planar and rotationally symmetric. Spatial noncommutativity leads the canonical angular momentum to possess fractional values. In the limit of vanishing kinetic energy, the dominate value of the lowest canonical angular momentum takes variant Planck's over h/2. Furthermore, in the limit of eliminating the magnetic field, the dominate value of the lowest canonical angular momentum changes from variant Planck's over h/2 to variant Planck's over h/4. This result is a clear signal of spatial noncommutativity. An experimental verification of this prediction is suggested.     

On the effects on a Landau-type system for an atom with no permanent electric dipole moment due to a Coulomb-type potential

We analyse the bound states for a Landau-type system for an atom with no permanent electric dipole moment subject to a Coulomb-type potential. By comparing the energy levels for bound states of the system with the Landau quantization for an atom with no permanent electric dipole moment (Furtado et al., 2006), we show that the energy levels of the Landau-type system are modified, where the degeneracy of the energy levels is broken. Another quantum effect investigated is a dependence of the angular frequency of the system on the quantum numbers associated with the radial modes and the angular momentum. As examples, we obtain the angular frequency and the energy levels associated with the ground state and the first excited state of the system.     

Anisotropic angular distribution of sputtered atoms

The sputtering yield angular distributions have been calculated on the basis of the ion energy dependence of total sputtering yields for Ni and Mo targets bombarded by low-energy Hg⁺ ions. The calculated curves show excellent agreement with the corresponding Wehner's experimental results of sputtering yield angular distributions. This fact clearly demonstrates the intrinsic relation between the ion energy dependence of total sputtering yields and the sputtering yield angular distribution. This intrinsic relation had been ignored in Yamamura's papers [Yamamura, Y. (1982). Theory of sputtering and comparison to experimental data, Nucl. Instr. and Meth., 194, 515–522; Yamamura, Y. (1981). Contribution of anisotropic velocity distribution of recoil atoms to sputtering yields and angular distributions of sputtered atoms, Rad. Eff., 55, 49–55.] due to some obvious mistakes.     

Calculation of photon angular distribution and polarization for radiative recombination for highly charged helium-like ions

A systematic study is carried out on the angular distribution and polarization of photons emitted following radiative recombination of He-like ions by a non-relativistic dipole approximation. In order to incorporate the screening effect due to inner-shell electrons, a distorted wave approach is used. The dependence of the calculated angular distribution and polarization on the reduced-energy and nuclear charge are fitted by the corresponding empirical formulas, respectively.     

Angular resolved UV photoemission from ordered layers of carbon monoxide on a nickel(100) surface

Angular resolved UPS measurements have been performed on the (√2 × √2)R45° and compressed structures of the adsorption system CO/Ni(100). Due to the operation of dipole selection rules the dependence of normal exit photoemission on angle of photon incidence is found to be a sensitive probe of initial state symmetry. The polar angular dependence of emission from the 4σ orbital follows closely that predicted by Davenport, provided that a correction for refraction and total photoelectron current conservation is applied. Such polar angular dependences show band shifts indicative of dispersion effects, which become more marked at higher CO coverages. An azimuthal angular dependence of emission was not observed despite the presence of ordered adlayers.     

Angular momentum misalignment in deep inelastic processes and angular distribution of sequentially emitted particles and gamma rays

The angular momentum misalignment for fragments produced in deep inelastic scattering is discussed in terms of the thermal excitation of angular-momentum-bearing modes in the intermediate complex. Analytical expressions for the in- and out-of-plane angular distributions are obtained for sequentially emitted particles and fission fragments. The angular momentum dependence of the ratio between particle and neutron decay widths is explicitly treated and found to be quite important. Similarly angular distributions are obtained both for dipole and quadrupole gamma decay. The theoretical results are compared with experimental angular distributions of sequential fission fragments, sequential alphas and gamma rays, and a good agreement is found.     

Nondipole ionization dynamics of atoms in superintense high-frequency attosecond pulses

The ionization of H(1s) in superintense, high-frequency, attosecond pulses is studied beyond the dipole approximation. We identify a unique nondipole 3rd lobe in the angular distribution of the ejected electron and show that this lobe has a well-defined classical counterpart. The ionization is likely to occur in the direction opposite to the laser propagation direction, which is fully understood from an analysis of the classical dynamics.     

Electric-field-induced symmetry breaking of angular momentum distribution in atoms

We report the experimental observation of alignment to orientation conversion in the 7D3/2 and 9D3/2 states of Cs in the presence of an external dc electric field and without the influence of magnetic fields or atomic collisions. Initial alignment of angular momentum states was created by two-step excitation with linearly polarized laser radiation. The appearance of transverse orientation of angular momentum was confirmed by the observation of circularly polarized light. We present experimentally measured signals and compare them with the results of a detailed theoretical model based on the optical Bloch equations. The effect is odd under time reversal and should be taken into account in ever more sensitive searches for an electron electric dipole moment.     

The angular distribution of photoelectrons from zinc atoms

The energy dependence of the photoelectron angular distribution of zinc was measured from 11.1 to 12.4 eV photon energy. The angular distribution parameterβ varies from 2 to ?1 in an autoionization resonance belonging to the configuration ...(3d)⁹(4s)²4p.     

Raman scattering of x-rays in crystals

The quantum theory for Raman scattering of x-rays by K electrons in crystals is given. The electrons ejected into the conduction band are described by plane waves. The expression obtained for the differential cross section has a Compton-like angular dependence in contrast to the results of Japanese physicists who used the dipole approximation in their work.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 9, pp. 26–28, September, 1971.     

On a relation of the angular frequency to the Aharonov–Casher geometric phase in a quantum dot

By analysing the behaviour of a neutral particle with permanent magnetic dipole moment confined to a quantum dot in the presence of a radial electric field, Coulomb-type and linear confining potentials, then, an Aharonov–Bohm-type effect for bound states and a dependence of the angular frequency of the system on the Aharonov–Casher geometric phase and the quantum numbers associated with the radial modes, the angular momentum and the spin are obtained. In particular, the possible values of the angular frequency and the persistent spin currents associated with the ground state are investigated in two different cases.     

Heavy particle scattering by atoms in an electric field

Atom—atom collision processes in an electric field are considered. A formula is obtained, in a two-level approximation, for the probability of transitions in which there is a change in the total angular momentum from J=0 to J=1. It is shown that the transition probability is characterized by an anisotropic distribution and a dependence on the electric field strength.V. V. Kuibyshev State University, Tomsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 91–94, October, 1994.     

Numerical simulations on the motion of atoms travelling through a standing-wave light field

The motion of metastable helium atoms travelling through a standing light wave is investigated with a semi-classical numerical model. The results of a calculation including the velocity dependence of the dipole force are compared with those of the commonly used approach, which assumes a conservative dipole force. The comparison is made for two atom guiding regimes that can be used for the production of nanostructure arrays; a low power regime, where the atoms are focused in a standing wave by the dipole force, and a higher power regime, in which the atoms channel along the potential minima of the light field. In the low power regime the differences between the two models are negligible and both models show that, for lithography purposes, pattern widths of 150 nm can be achieved. In the high power channelling regime the conservative force model, predicting 100 nm features, is shown to break down. The model that incorporates velocity dependence, resulting in a structure size of 40 nm, remains valid, as demonstrated by a comparison with quantum Monte-Carlo wavefunction calculations.Received: 11 December 2002, Published online: 29 July 2003PACS: 02.60.Cb Numerical simulation; solution of equations - 32.80.Lg Mechanical effects of light on atoms, molecules, and ions - 81.16.Rf Nanoscale pattern formationL. Feenstra: Present address: Physikalisches Institut, Universität Heidelberg, Philosophenweg 12, 69120 Heidelberg, Germany.     

Atomic dipole moment distribution of Si atoms on a Si111-(7 x 7) surface studied using noncontact scanning nonlinear dielectric microscopy

A local atomic electric dipole moment distribution of Si atoms on Si(111)-(7 x 7) surface is clearly resolved by using a new technique called noncontact scanning nonlinear dielectric microscopy. The dc-bias voltage dependence of the atomic dipole moment on the Si(111)-(7 x 7) surface is measured. At the weak applied voltage of -0.5 V, a positive dipole moment is detected on the Si adatom sites, whereas a negative dipole moment is observed at the interstitial sites of inter Si adatoms. Moreover, the quantitative dependence of the surface dipole moment as a function of the applied dc voltage is also revealed at a fixed point above the sample surface. This is the first successful demonstration of direct atomic dipole moment observation achieved in the field of capacitance measurement.