K. Tőkési

Simulation of attosecond streaking of electrons emitted from a tungsten surface

First time-resolved photoemission experiments employing attosecond streaking of electrons emitted by an extended ultraviolet pump pulse and probed by a few-cycle near-infrared pulse found a time delay of about 100 as between photoelectrons from the conduction band and those from the

Monte Carlo modelling of the backscattered electron spectra of silver at the 200 eV and 2 keV primary electron energies

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A distorted field cylindrical mirror electron analyzer II Performances and application for studying ion-atom collisions

core level of tungsten. We present a microscopic simulation of the emission time and energy spectra employing a classical transport theory. Emission spectra and streaking images are well reproduced. Different contributions to the delayed emission of core electrons are identified: larger emission depth, slowing down by inelastic-scattering processes, and possibly, energy-dependent deviations from the free-electron dispersion. We find delay times near the lower bound of the experimental data.

Existence of the electron capture to the continuum peak at positron impact

Abstract The electron energy distribution of the backscattered electrons from a polycrystalline silver sample was studied in the direction of the surface normal of the specimen, at the 200 eV and 2 keV energy of the primary beam. The angle of the incident electron beam was 50° with respect to the surface norm. For simulation of the backscattered electron energy distributions the Monte Carlo technique was used and the computed spectra were compared to the measured reflected electron spectra in the energy range of few times 10 eV from the elastic peak. The probable reasons of the observed discrepancies between the measured reflected electron energy loss spectra and the calculated spectra are discussed. In addition, the yield of the backscattered electrons as a function of the number of elastic and inelastic collisions is compared for different parts of the backscattered electron spectra.

Design of an electrostatic electron spectrometer for simultaneous energy and angular distribution measurements

Abstract A distorted electrostatic field tandem cylindrical mirror electron analyzer (ESA-13) has been developed based on the numerical calculation published earlier. The measured parameters have verified the calculated ones. The relative energy resolution is found to be around ΔE E = 0.3% , without pre-retardation. The spectrometer is capable of analyzing electrons in the whole angular range (0°–180°) of the scattering plane with small acceptance angle and fine angular steps (0.25°).

Experimental setup for studying guiding of proton microbeam

Abstract A three-body classical trajectory Monte Carlo (CTMC) method is used to describe the ionization cross sections in positron–argon collisions. The existence of the cusp-like peak at positron impact is shown.

RESEARCH ON ELECTRON IMPACT INNER-SHELL IONIZATION BY MEANS OF THE MEASUREMENT OF POST-COLLISION INTERACTION

Abstract The calculated electron optical properties of a new mirror type analyser with distorted cylindrical field are presented here. Two different analyser elements and a double-pass spectrometer based on these elements were designed. A spectrometer having such a construction can be suitable for measuring both energy and angular distributions of electrons simultaneously, in the full range of scattering angle (0°–180°) with high energy resolution.

An electrostatic lens for zero-degree electron spectroscopy

We present the design and construction of our experimental setup for studying the transmission of proton microbeam through a single, cylindrical shape, macroscopic insulating capillary. The intensity as a function of time, the energy distribution as a function of the transmission and the deflection of the transmitted particles can be measured with the new setup.

Continuous electron spectra from 150 keV/u C+ + He, Ne, Ar collisions at electron emission angles from 0° to 180°

Abstract The distortion effects of the post-collision interaction (PCI) in argon L 2,3 M 2,3 M 2,3 Auger electron spectra following the electron impact inner-shell ionization of argon are studied in a wide energy range. The accurate measurements of these distortions are compared with theoretical calculations based on the model of Sheinerman et al. (S.A. Sheinerman, W. Kuhn, W. Mehlhorn, J. Phys. B 27 (1994) 5681). An excellent agreement between theory and experiment was found. Moreover, the existence of a not vanishing PCI shift in the high-energy region is confirmed.

Absolute determination of optical constants by reflection electron energy loss spectroscopy

Abstract A multi-element electrostatic lens was constructed to improve the energy analysis of electrons ejected at zero degree in ion-atom collisions. The lens, coupled to a cylindrical mirror analyser, considerably extends the energy range of the analyser to lower energies by acceleration of the electrons, and improves its angular resolution by angular magnification. The distribution of the potential in the lens was determined using series expansion, starting from a given function of potential at the lens axis. The electron-optical properties of the lens were obtained from ray tracing. The power of the lens is demonstrated taking the spectrum of electrons emitted from He− on Ar collisions at 112 keV impact energy, in which the auto-ionization peaks originating from the (1s2p2p′) 4Pe shape resonance of He− are completely resolved.