Multielectron spectroscopy: the xenon 4d hole double auger decay

A magnetic bottle spectrometer of the type recently developed by Eland et al. [Phys. Rev. Lett. 90, 053003 (2003).] has been implemented for use with synchrotron radiation, allowing multidimensional electron spectroscopy. Its application to the Xe 4d double Auger decay reveals all the energy pathways involved. The dominant path is a cascade process with a rapid (6 fs) ejection of a first Auger electron followed by the slower (>23 fs) emission of a second Auger electron. Weaker processes implying 3 electron processes are also revealed, namely, direct double Auger and associated Rydberg series.     

Cross-sections for rotational excitations of C3H4 isomers by electron impact

We report elastic (rotationally summed) and rotationally resolved cross-sections for scattering of low-energy electrons by the C₃H₄ isomers allene, propyne, and cyclopropene, which belong to the D_2d, C_3v, and C_2v groups, respectively. We employed the Schwinger multichannel method with pseudopotentials at the static-exchange approximation, combined with the adiabatic-nuclei-rotation (ANR) approximation to calculate the rotational excitation cross-sections for energies ranging from 5 to 30 eV. Our rotational resolved cross-sections show the isomer effect more strongly related to scattering potentials of different molecular geometries and to transition selection rules than to differences in mass distribution which account for the energy spacing in the rotational spectra of the molecules.     

Charge excitations in heavy electron metals

We show that the optical response of metals with strong electron-electron correlation consists of two excitations, a renormalized Drude response at zero energy and a mid-infrared peak occurring at frequencies around 2000 cm^-1. The latter originates from a dynamical, correlation-induced gap, as evinced from a many body theoretical approach based on the periodic Anderson model. At very low temperatures, it can be viewed as optical gap between two renormalized quasi-particle bands. The gap size is proportional to the geometric mean of the characteristic lattice Kondo temperature of the material and its bandwidth. Received 28 August 2000 and Received in final form 31 October 2000     

Elementary excitations in tunnel-coupled electron bilayers

A new class of single-particle excitations in tunnel-coupled electron bilayers is investigated by inelastic light scattering. The dispersion law and the dependence of the energies of these excitations on the degree of unbalance between the layers have been measured. A new spectroscopic method is proposed for determining the degree of unbalance between bilayers.     

Excitonic luminescence spectrum of electron excited solid xenon

The luminescence spectrum of electron excited solid Xenon shows a broad structure around 1750 Å attributed to molecular excitons (excimers) and sharp excitonic lines around 1500 Å.     

Relativistic and distorted wave effects on Xe 4d electron momentum distributions

The relativistic and distorted wave effects are investigated for the electron momentum distributions of Xe 4d electrons.The theoretical results show good agreements with the experimental data measured previously with electron momentum spectroscopy. The distorted wave effect and the relativistic effect are found to play important roles in the low and high momentum regions, respectively.     

Collective magnetoplasma excitations in two-dimensional electron rings

The spectra of magnetoplasma excitations in two-dimensional electron disks and rings are studied by optical detection of resonance microwave absorption. For ring-shaped structures, two types of edge magnetoplasma modes localized along the inner and outer boundaries of the ring are observed. It is shown that the interaction between these modes leads to a strong modification of their magnetic-field dependences as compared to disks. In addition to the longitudinal edge magnetoplasma excitations, transverse plasma modes associated with the electron density oscillations along the ring radius are revealed. The spectra of magnetoplasma excitations are calculated in terms of the electrodynamic theory for both ring-shaped and disk-shaped structures. The classification of all modes of collective magnetoplasma excitations observed in the experiment is performed on the basis of the comparison between experimental and theoretical results.     

Acoustic magnetoplasma excitations in double electron layers

The inelastic light scattering technique is used to study the spectra of intraband excitations of the quasi-two-dimensional electron system in GaAS/AlGaAs double quantum wells. A new collective mode, namely, the acoustic plasmon, is discovered and investigated. The dispersion law of the acoustic mode and its dependence on the electron density are measured. It is shown that, in a perpendicular magnetic field, a hybridization of the acoustic plasmon with the cyclotron mode takes place. The properties of the hybrid acoustic magnetoplasma collective excitations are studied.     

Anions of xenon clusters bound by long-range electron correlations

In contrast with the single atom, atomic van der Waals clusters can form stable anions where the excess electron is bound due to long-range correlations with the electrons of the cluster. We report on extensive all-electron many-body ab initio studies on Xe clusters. Three-dimensional, planar, and linear structures of the clusters are investigated and compared. In particular, we find that the minimal number of Xe atoms in the cluster required to form a stable anion is 5 independently of the dimensionality of the cluster. We provide electron affinities for clusters made of 5, 6, and 7 atoms in all dimensions and find that the planar clusters form the most stable anions. The Dyson orbitals of the excess electrons are computed and analyzed.     

Spectral analysis of the 4d6s configuration in eight times ionized xenon, Xe IX

A capillary light source was used to observe the spectrum of eight times ionized xenon, Xe IX, in the vacuum ultraviolet range, 270-2000 Å. Sixteen transitions have been identified as combinations between energy levels of the 4d⁹6s with 4d⁹5p configuration, and all 4d⁹6s levels have been determined. The present analysis is based on an accurate extrapolation of energy parameters and experimental energy level values in the Pd I isoelectronic sequence. The energy parameters were obtained with Hartree-Fock relativistic calculations. Least-squares parametric calculation has been carried out to study the fit between experimental and theoretical values.     

Collective excitations in low-density 2D electron systems

We report the observation of sharp plasmon and magnetoplasmon modes in ultra-low-density 2D electron systems. Well defined dispersions for the modes are observed at densities as low as 1.1×10⁹ cm⁻² and with excitation wave vectors as large as 1.2×10⁵ cm⁻¹. Interestingly, both modes are found to be more easily measured in low-density systems than in high-density systems. The strength of the light scattering cross-sections at low density suggests potential applications to the study of quantum phase transitions at large r_s.     

Light scattering from non-equilibrium electron excitations in semiconductors

Light scattering from non equilibrium single-particle electron excitations in direct gap n-doped semiconductors is considered. It is shown that, in quasi-equilibrium conditions, deviations from the Maxwellian profile of the scattering spectrum of hot electrons can be accounted for by exchange and correlation effects.     

Collective electron excitations in 3D graphite clusters

Group-theoretical analysis and subsequent quantum-chemical calculations based on the molecular orbital method applied to a cyclic model of 3D semimetallic graphite lead to a multiplet of spectroscopic combinations of Slater determinants. The transition energies ΔE between terms of the multiplet are interpreted as the energies of collective electron mesoscopic excitations ?ω in the entire set of electron states characterizing the metal-type conductivity of a cluster. The estimate ?ω～0.2ΔE(N ₀/1000)^2/3 is obtained for a cluster consisting of N ₀ primitive cells. Depending on the thermal processing, N ₀=(0.3–20)×10⁶ in pyrolytic graphite, and accordingly ?ω～(10–150) eV. In the case when the energy cannot be determined accurately, methods permitting the variation of an excitation over a wide range (such as the spectroscopy of synchrotron radiation absorption and the characteristic energy losses of charged particles) appear to be the most promising.     

Xe9+离子4d9-4d85p跃迁的理论研究

 利用多组态Dirac-Fock(MCDF)方法，通过对Xe⁹⁺离子4d⁹-4d⁸5p跃迁的系统计算，研究了电子相关效应对Xe⁹⁺离子4d⁹-4d⁸5p跃迁的影响，给出了相应的跃迁能和辐射跃迁几率，并与最新的实验观测和其它理论计算结果进行了比较。计算结果表明：电子的关联效应显著。根据计算结果和实验结果的一致性和两个规范下所得的跃迁几率的一致性，可以认为本文的计算结果是可信的。