D Šević

Experimental determination of the differential cross-section surface for elastic electron?atom (molecule) scattering

A crossed-beam experimental set-up, which allows independent measurement of differential electron–atom (molecule) elastic scattering cross section as a function of both scattering angle and incident electron energy, is described. The experimental system utilizes an electron gun and a double cylindrical mirror analyser, which are described in detail. A procedure for obtaining constant scattering geometry, transmission function and detection efficiency, in a wide range of the incident electron energies (40–250 eV), was tested experimentally and by means of electron trace simulations. The present experimental procedure allows determination of a two-dimensional relative differential cross-section surface, which can be calibrated to the absolute scale via normalization to a single point.

Electron-impact excitation of the (n- 1)d9ns2np autoionizing states of cadmium (n = 5) and zinc (n=4)

Electron-impact excitation of the 53P 1 (12.062 eV) and 51P 1 (12.810 eV) 4d95s25p autoionizing states of Cd has been experimentally investigated at incident electron energies (E0) from 15 to 60 eV and scattering angles (θ) up to 40° (at E0 = 40 eV, θ = 2°–150°). The absolute differential cross sections (DCSs) at E0 = 40 eV were determined through normalization to the optical oscillator strengths. These DCSs were extrapolated to 0° and 180° and numerically integrated to yield integral, momentum transfer and viscosity cross sections. Energy-loss spectra for Cd were recorded from 11 to 18 eV, and 22 autoionizing states were identified at different impact energies. Electron-impact excitation of the 3d94s24p autoionizing states was observed in energy-loss spectra of Zn at E0 = 20, 60, 80 and 100 eV (θ up to 10°). The DCSs for Cd could not be compared with other results, because there are no available data in literature. The autoionizing energy levels and line widths are in good agreement with existing experimental and calculated values.

Electron scattering by ytterbium: I. Excitation of the 4f146s6p 1P1 resonance state and elastic collision

Differential cross sections (DCSs) for electron-impact excitation of the 4f 14 6s6p 1 P1 resonance state of ytterbium were measured at 10, 20, 40, 60 and 80 eV incident electron energies (E0) and scattering angles (θ ) between 2 ◦ and 150 ◦ . The absolute DCS scale for the 1 P1 state was determined through normalization of its relative DCSs to the optical oscillator strength using the forward scattering function method. DCSs for elastic electron scattering by ytterbium were measured at the same energies for θ between 10 ◦ and 150 ◦ . Elastic-to-inelastic intensity ratios were obtained from energy-loss spectra recorded with overall energy resolution of 65 meV (FWHM) and angular resolution of 1.5 ◦ . Both inelastic and elastic DCSs were extrapolated to 0 ◦ and 180 ◦ and numerically integrated to yield integral, momentum transfer and viscosity cross sections. Our results are compared with scarce experimental and theoretical data.

Differential and integrated cross sections for the electron excitation of the 4 1Po state of calcium atom

Differential cross section (DCS) data for excitation of the 4 1Po state (2.93 eV) of Ca atoms by electrons have been obtained using a crossed electron–atom beam technique. The measurements were divided into two groups. The first one consists of measurements at 10, 20, 40, 60 and 100 eV impact electron energies from 1° to 10° scattering angle interval. The second group of measurements are those at larger scattering angles (10°–150°) at the same energies except 100 eV. Absolute values have been obtained by normalizing generalized oscillator strengths (GOS) to optical oscillator strength (OOS) in the minimum momentum transfer squared (K2) limit. Integral, momentum transfer and viscosity cross sections have been determined from DCSs. A comparison is made with existing relativistic distorted wave calculation.

Elastic electron scattering by a magnesium atom

Absolute differential cross sections (DCSs) for elastic electron scattering by a magnesium atom at incident electron energies of 10, 15, 20, 40, 60, 80 and 100 eV have been experimentally derived. The scattered electron intensities were measured over a wide range of scattering angles (θ) from 10° to 150°. The elastic-to-inelastic (3s3p 1P1 resonance state) intensity ratios at θ = 10° were measured separately. These ratios and DCSs for the resonance state (by Filipovic et al 2006 Int. J. Mass Spectrom. 251 66) were applied for the normalization. The absolute DCSs were extrapolated to 0° and 180° and then integrated to yield integral cross sections. The results were analysed and compared with available experimental data and theoretical calculations.

Differential and integrated cross sections for the elastic electron scattering by calcium atom

The experimental and theoretical studies of elastic electron scattering by calcium atom have been made. The experimental investigation was carried out using a crossed electron-atom beam technique. The measurements were performed at electron-impact energies (E0) of 10, 20, 40, 60 and 100 eV and for a range of scattering angles (θ) from 10° up to 150°. The absolute differential cross sections (DCSs) have been obtained from the elastic-to-inelastic (the resonant 41P0 state) intensity ratio at θ = 10° at each E0. Calculations have been performed in the optical potential approximation for the same E0 and θ between 0° and 180°. Results for DCSs and integrated (integral, momentum transfer and viscosity) cross sections are presented and compared with those predicted by existing calculations.

Time-Resolved LIBS Streak Spectrum Processing

The laser-induced breakdown spectroscopy (LIBS) is a sensitive tool for a rapid identification of the elemental composition of a sample regardless of the aggregate states and with a little sample preparation. The time-resolved LIBS system implemented in our laboratory is based on a Nd:YAG laser and an optical parametric oscillator (Vibrant 266). The detection part of our system is based on a Hamamatsu streak camera (C4334-01). Using advanced image processing techniques, we show how capabilities of basic software provided by Hamamatsu could be improved.

Electron scattering by ytterbium: II. Excitation of the 4f14(6s6p 3P1, 5d6s 1D2 and 6s7p 1P1) and 4f135d6s2 (7/2, 5/2)1 states

Differential cross sections (DCSs) for electron-impact excitation of the 4f146s6p3P1 (2.231 eV) state of ytterbium have been determined experimentally at incident electron energies, E0 = 10, 20 and 40 eV, and scattering angles (?) from 2? to 150? (at 10 eV from 10?). Also, DCSs for the 4f145d6s 1D2 (3.432 eV) and 4f135d6s2 (7/2, 5/2)1 (3.578 eV) states at E0 = 10 and 20 eV, and the 4f146s7p 1P1 (5.029 eV) state at 20 and 40 eV have been measured. These measurements were performed at ? between 10? and 150? for the 4f145d6s 1D2 and 4f135d6s2 (7/2, 5/2)1 states, and between 2? and 150? for the 4f146s7p 1P1 state. The inelastic-to-reference inelastic (the 4f146s6p 1P1 resonance state) intensity ratios were obtained from energy-loss spectra recorded with overall energy resolution of 65 meV (FWHM) and angular resolution of 1.5?. Using these ratios and DCSs for the reference state (Predojevi? et al 2005 J. Phys. B: At. Mol. Opt. Phys. 38 1329) the absolute inelastic DCSs were determined. In this way the obtained DCSs were extrapolated to 0? and 180? and numerically integrated to yield integral, momentum transfer and viscosity cross sections. Our results are compared with available calculated values and experimental data.

Time-Resolved Optical Spectra of the Laser-Induced Indium Plasma Detected Using a Streak Camera

We present time-resolved laser-induced breakdown spectroscopy (LIBS) spectra of atomic (In I) and ionic (In II) indium lines recorded in time ranges from 500 ns to 20 μs. Optical spectra have been acquired using a streak camera. Since it is assumed that the available supply of indium will slowly but inevitably diminish, the recycling of indium and finding the new natural sources are more and more important as the price of indium rises. The study of indium lines showed in this paper could be useful for making the LIBS detecting devices less expensive and more portable.

Comparison of beetroot extracts originating from several sites using time-resolved laser-induced fluorescence spectroscopy

Beetroot (Beta vulgaris) juice contains a large number of fluorophores which can fluoresce. There is a growing interest in beetroot extracts analysis. In contrast, there is only limited information about beetroot obtained without sample preparation and/or extraction of components from the sample. In this work, we continue our previous study (Rabasovic et al 2009 Acta Phys. Pol. A 116 570–2), analyzing and comparing beetroot extracts from several sites, using the time-resolved laser-induced fluorescence technique to measure the fluorescence of samples at different excitation wavelengths (340–470 nm) and for different sample dilutions.