Measurement of the energy dependences of the photoelectron angular distribution parameters for Ar 3p and Kr 4p electrons using an electron-electron coincidence experiment

The energy dependence of the photoelectron angular distribution parameter (β) has been measured for Ar 3p and Kr 4p electrons in the energy ranges 4–54 eV and 4–40 eV above threshold respectively, using 3.5 keV electron impact with coincidence detection of the scattered and ejected electrons. This energy range is considerably greater than that covered in previous experiments. The data over the whole energy range are compared with the Hartree-Fock calculations of Kennedy and Manson and with those of Amusia et al., using the random phase approximation with exchange method. For Ar the calculations of Amusia et al., which take into account many-electron correlations, are shown to agree more closely with the present data. The data are also shown to be in very good agreement with earlier experimental data obtained over a more limited energy range using electron synchrotron radiation.     

The angular distribution of neon 2p shell photoelectrons in the 0–20 eV region above threshold

The photoelectron angular distribution parameter β has been measured in the 0–20 eV region above threshold for the neon 2p electrons using a synchrotron light source. Measurements are compared with the Hartree-Fock calculations of Manson and Kennedy.     

(e,2e) and (e,3-1e) coincidence experiments for studying the PCI effect of low energy ionizing electrons in the Auger process of Ar

Our (e,3-1e) measurements for studying the post-collision interaction (PCI) after electron impact inner shell ionization of argon were continued and completed at different energy conditions. Emitted LMM Auger electrons are detected in coincidence with the ionizing scattered electrons and the energy of the slow PCI inducer ejected electron was calculated from energy conservation. Particularly the effect of the very low energy (i.e. 0–5 eV) ejected electrons (strongly asymmetric energy sharing) is studied at 500 and 460 eV primary electron energies. In the latter case, the background caused by outer-shell electrons was measured by itself and then removed from the coincident spectrum. Nevertheless, the evaluation of PCI distorted Auger lines is still considerably disturbed by the resonant Auger electrons from the high Rydberg states, their (e,2e) contribution was estimated in the paper.     

Excitation of even configurations of a nickel atom containing nine 3d electrons

The electron-impact excitation of even levels of the nickel atom belonging to configurations that contain nine 3d electrons is studied by the method of extended crossing beams. Ninety-six excitation cross sections are measured at an exciting electron energy of 50 eV. Seven optical excitation functions are recorded in the exciting electron energy range of 0–200 eV. Total excitation cross sections are determined for 24 energy levels of the nickel atom.     

Elastic scattering of electrons by argon atoms

The partial wave method with a central potential has been applied to investigate the elastic scattering of electrons by the argon atoms in the intermediate energy range (100 eV − 1 keV). The central potential includes the effects of the static field, exchange and polarization. The results are in good accord with recent experimental data. A brief account of this investigation was presented at the X Int. Conf. on the Physics of Electronic and Atomic Collisions held at Paris in July 1977.     

Drift mobility of electrons in TlSbS2

The time-of-flight technique has been used to study the transport of electrons in TlSbS₂ in the perpendicular direction with respect to the cleavage planes. The transport of electrons is non-dispersive and can be considered an activated process with an activation energy of 0·40 eV. The value of 1·68 eV has been found for the energy gap of TlSbS₂ at room temperature.     

Experimental determination of the mean scattering length of low energy electrons in bismuth

The mean scattering length of electrons emitted in the Auger decay of Sb4d core holes in Sb₂Te₃ and propagating through thin Bi films has been experimentally determined for energies ～5 to 12 eV above the Fermi level.     

Excitation of lowest electronic states of the uracil molecule by slow electrons

The excitation of lowest electronic states of the uracil molecule in the gas phase has been studied by electron energy loss spectroscopy. Along with excitation of lowest singlet states, excitation of two lowest triplet states at 3.75 and 4.76 eV (±0.05 eV) and vibrational excitation of the molecule in two resonant ranges (1?C2 and 3?C4 eV) have been observed for the first time. The peak of the excitation band related to the lowest singlet state (5.50 eV) is found to be blueshifted by 0.4 eV in comparison with the optical absorption spectroscopy data. The threshold excitation spectra have been measured for the first time, with detection of electrons inelastically scattered by an angle of 180°. These spectra exhibit clear separation of the 5.50-eV-wide band into two bands, which are due to the excitation of the triplet 1³ A?? and singlet 1¹ A?? states.     

Branching ratios and the partial photoionization cross-section for the 3s electron of argon

Binding-energy spectra obtained using the dipole (e, 2e) electron impact coincidence method have been used to derive the 3s/3p cross-section ratios for the photoionization of argon up to 75 eV. The 3s and 3p photoionization branching ratios have been obtained by making use of recently determined double photoionization yields. The partial photoionization cross-section (oscillator strength) for 3s ionization, obtained using the branching ratio and the known total photoionization cross-section, shows the deep minimum ca. 10 eV above threshold which has been predicted by those theoretical calculations which include electron correlation effects. Below 50 eV the cross-section is in excellent agreement with the SRPAE calculation. The results are in close agreement with recent measurements made using synchrotron radiation but are consistently smaller below the minimum and larger at the higher energies.     

Elastic scattering of electrons by atomic hydrogen at intermediate energies

The improved second Born computational method of Das has been used in computing the differential cross section for the elastic scattering of electrons by atomic hydrogen at intermediate energies (in the range 20–50eV). The results show that the method of Das works nicely down to energies of 20 eV.     

Elastic scattering of electrons by hydrogen molecules

Elastic scattering of electrons by hydrogen molecules has been investigated in the intermediate energy range 100–2000 eV. The direct scattering amplitude consists of first Börn and second Börn minus distortion term. The contribution of exchange has been included through Ochkur approximation. The elastic differential cross-sections agree with experimental data.     

Excitation cross-sections of 3 F-and 3 F o-levels of barium atom by slow electrons

Excitation of the ³F-and ³F^o-levels of barium atom by slow electrons has been investigated experimentally. A total of 75 excitation cross-sections were measured at 30-eV electron energy; 20 optical excitation functions, in the range 0–200 eV electron energy. The behavior of cross-sections in some spectral series of BaI is discussed. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 6, pp. 757–762, November–December, 2008.     

Double photoionization of helium down to 100 meV above threshold

Double photoionization of helium has been studied using a new instrument which allows one to detect the two emitted electrons over 4 pi steradians and measure their individual momenta. The experiments have been performed at 0.2 and 0.1 eV above threshold, and both double and triple differential cross sections have been extracted. In comparison with higher energy data, the results show that the strength of angular correlation between the two electrons increases towards threshold.     

Elastic scattering of electrons from tetrahydrofuran molecule

Absolute differential cross-sections (DCSs) for elastic scattering of electrons from the DNA backbone sugarlike analogue tetrahydrofuran (THF) molecule were determined using a crossed beam measurements for incident energies from 20 eV to 300 eV and scattering angles from 10^o to 110^o. Using the relative-flow technique, elastic DCSs for THF relative to nitrogen have been obtained at incident energies of 20, 30, 40, 50 and 60 eV. In the energy region above 30 eV, the DCSs were measured independently as a function of both incident electron energy and scattering angle. Therefore, this set of relative DCSs has been calibrated to the absolute scale via normalization to a single point in the overlapping region. Additionally, both vibrational and electronic energy loss spectra for THF are presented and influence of energy resolution to the obtained DCSs is discussed.     

The negative role of the fast electrons in the microwave oxidation of silicon

The influence of the fast electrons (up to approx. 100 eV), created in the magnetoactive oxygen plasma, with respect to the silicon oxide growth and oxide properties has been studied. The low values of the oxide dielectric strength and great density of the oxide defect charges have been found on damaged oxides. An upper energy limit (less than approx. 30 eV) has been introduced for the plasma electrons to prevent the oxide defects and extremal heating of the silicon sample during oxidation process.     

High resolution threshold photoelectron spectra of neon and argon in the valence satellite region

Using a newly designed zerovolt-electron spectrometer, high resolution threshold photoelectron spectra of neon above the 2s and of argon above the 3s photoelectron thresholds were taken following excitation with synchrotron radiation. From these spectra we were able to derive quantitatively the multiplet splitting of two neon satellites and almost all argon photoelectron satellites up to 38eV. Strong deviations from statistical behavior of most multiplet components were found. This unusual behavior is explained by autoionization of double-excited neutral states into the continuum of the satellite states just above threshold.     

Mechanisms of photo double ionization of helium by 530 eV photons

We have measured fully differential cross sections for photo double ionization of helium 450 eV above the threshold. We have found an extremely asymmetric energy sharing between the photoelectrons and an angular asymmetry parameter beta approximately 2 and beta approximately 0 for the fast and slow electrons, respectively. The electron angular distributions show a dominance of the shakeoff for 2 eV electrons and clear evidence of an inelastic electron-electron scattering at an electron energy of 30 eV. The data are in excellent agreement with convergent close-coupling calculations.     

Characteristic losses of electrons and the electron structure of thallium chloride

The complete set of fundamental optical functions of a thallium chloride crystal is calculated on the basis of the familiar experimental spectrum of volume characteristic losses of electrons using the Kramers-Kronig relations in a range of 0–25 eV. The loss and permittivity spectra are decomposed into elementary components and their main parameters are determined. Basic features of integrated and decomposed spectra are established.     

The electronic structure of SrTiO3 from a direct-transition analysis of angle-resolved photoemission data

Angle-resolved photoemission spectra of SrTiO₃(100) have been recorded in the range 18eV⩽ hν⩽ 50eV. The results have been interpreted using a direct transition model and a free-electron like final state, yielding empirical Δ-line dispersion relations. While in overall agreement with available band structure calculations, significant discrepancies are revealed. In addition, resonance photoemission above the Ti 3p threshold has been used to identify regions of Ti 3d mixing in the mainly 0 2p valence bands, the results being consistent with theoretical models.     

(e,3e) on helium at low impact energy: the strongly correlated three-electron continuum

Double ionization of the helium atom by slow electron impact (E(0)=106 eV) is studied in a kinematically complete experiment. Because of a low excess energy E(exc)=27 eV above the double ionization threshold, a strongly correlated three-electron continuum is realized. This is demonstrated by measuring and calculating the fully differential cross sections for equal energy sharing of the final-state electrons. While the electron emission is dominated by a strong Coulomb repulsion, also signatures of more complex dynamics of the full four-body system are identified.