arXiv subjects

K. Tokesi

Publications and source records attributed to K. Tokesi.

5 recordsLinked to original sources

arXiv2024

Orbital Collapse in Exotic Atoms and Its Effect on Dynamics

We study the energy structures of muonic Ar atoms and find the muon orbital collapses at a critical angular momentum $l_c$ using density-functional theory (DFT). The $l_c$ may provide an upper limit for the muon-captured states in muon-Ar collisions. We confirm the existence of this upper limit by calculating the state-specified capture probability using the time-dependent Schr\"odinger equation (TDSE) and a classical trajectory Monte Carlo (CTMC) methods with the single-active-particle approximation. Modifying the mapping between the classical binding energy and the principal quantum number led to a reasonable agreement in the state-specified muon capture probabilities obtained by the TDSE and CTMC methods. We also propose a simple method to estimate $l_c$ for exotic noble atoms from atomic model potentials. The estimated values agree with those calculated by DFT.

physics.atom-ph↗

arXiv2016

Absolute Determination of Optical Constants by a Direct Physical Modeling of Reflection Electron Energy Loss Spectra

We present an absolute extraction method of optical constants of metal from the measured reflection electron energy loss (REELS) spectra by using the recently developed reverse Monte Carlo (RMC) technique. The method is based on a direct physical modeling of electron elastic and electron inelastic scattering near the surface region where the surface excitation becomes important to fully describe the spectrum loss feature intensity in relative to the elastic peak intensity. An optimization procedure of oscillator parameters appeared in the energy loss function (ELF) for describing electron inelastic scattering due to the bulk- and surface-excitations was performed with the simulated annealing method by a successive comparison between the measured and Monte Carlo simulated REELS spectra. The ELF and corresponding optical constants of Fe were obtained from the REELS spectra measured at incident energies of 1000, 2000 and 3000 eV. The validity of the present optical data has been verified with the f- and ps-sum rules showing the accuracy and applicability of the present approach. Our data are also compared with previous optical data from other sources.

cond-mat.mtrl-sci↗

arXiv2009

Simulation of attosecond streaking of electrons emitted from a tungsten surface

First time-resolved photoemission experiments employing attosecond streaking of electrons emitted by an XUV pump pulse and probed by a few-cycle NIR pulse found a time delay of about 100 attoseconds between photoelectrons from the conduction band and those from the 4f 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.

cond-mat.other↗

arXiv2009

Electron guiding through insulating nanocapillaries

We simulate the electron transmission through insulating Mylar (PET) capillaries. We show that the mechanisms underlying the recently discovered electron guiding are fundamentally different from those for ion guiding. Quantum reflection and multiple near-forward scattering rather than the self-organized charge-up are key to the transmission along the capillary axis irrespective of the angle of incidence. We find surprisingly good agreement with recent data. Our simulation suggests that electron guiding should also be observable for metallic capillaries.

cond-mat.other↗

arXiv2005

Simulation of guiding of multiply charged projectiles through insulating capillaries

Recent experiments have demonstrated that highly charged ions can be guided through insulating nanocapillaries along the direction of the capillary axis for a surprisingly wide range of injection angles. Even more surprisingly, the transmitted particles remain predominantly in their initial charge state, thus opening the pathway to the construction of novel ion-optical elements without electric feedthroughs. We present a theoretical treatment of this self-organized guiding process. We develop a classical trajectory transport theory that relates the microscopic charge-up with macroscopic material properties. Transmission coefficients, angular spread of transmitted particles, and discharge characteristics of the target are investigated. Partial agreement with experiment is found.

physics.atom-ph↗