Multi-paraméteres elektron-spektroszkópiai kutatások ionok, atomok és molekulák gerjesztett állapotainak vizsgálatára = Multi-parameter analyses for investigating the excited states of ions, atoms and molecules using electronspectroscopy

A fotoelektronok szögeloszlását jellemző dipól és nem-dipól anizotrópia paramétereket határoztunk meg Xe 5s, 5p1/2,3/2 és Ar 3p1/2,3/2 alhéjak esetében. A méréseket a lundi Max-2 szinkrotronnál az ESA-22L jelű elektron-spektrométerrel végeztük. Először sikerült külön-külön meghatároznunk mind a három héj esetében az anizotrópia paramétereket. Vizsgálataink egyértelműen bizonyítják, hogy a direkt és indirekt fotoionizációs folyamatok között jelentős interferencia van. A szögeloszlások részletes vizsgálatakor kimutattuk, hogy a jobb és bal oldali intenzitás (az impulzus vektorra mint szimmetria tengelyre nézve) nem azonos. A részletes kísérleti vizsgálatok egyértelműen bizonyították, hogy a jelenség nem kísérleti hiba következménye, hanem valós effektus, amely esetleges paritás sértésre utal fotoionizációnál. Kimutattuk, hogy a folytonos energiájú állapotokba történő elektronbefogás (ECC) folyamatot jellemző csúcs jelentősen eltolódik 50 eV-es pozitron lövedék esetében az elméleti értékhez képest. Úgy találtuk, hogy az ütközés utáni kölcsönhatás jóval erősebb, mint amit, a rendelkezésre álló elméletek jósolnak. Elkészült Debrecenben az ESA-22D jelű analizátor és a mérést vezérlő szoftver, amelyet elsősorban szilárd mintákból, különböző folyamatok során emittált elektronok energia- és szögeloszlásának tanulmányozására kívánunk használni. Első alkalmazásként amorf szilícium mintában elektronütközés révén keltett felületi és térfogati plazmonokat vizsgáltunk. | The dipole and non-dipole parameters were determined for the angular distribution of photoelectrons ejected from Xe 5s, 5p1/2,3/2 and the Ar 3p1/2,3/2 sub-shells. The investigations were carried out at the Max-2 synchrotron with the ESA-22L electron-spectrometer. This was the first time when the three anisotropy parameters were determined separately. Our investigations clearly showed the existence of a strong interference between the direct and indirect photoionization process. The detailed analysis of the angular distributions showed a left-right asymmetry relative to the momentum vector of the photon. In order to verify this finding, careful experimental investigations were carried out. The results confirmed the existence of the asymmetry, indicating a possible parity violence in photoionization. An energy shift was found at the cusp peak (which is the result of the electron capture to the continuum process, ECC) relative to the theoretical value at 50 eV positron-H2 collisions. The detailed investigation showed that the strength of the post collision interaction is stronger than the theoretically predicted values. The ESA-22D electronspectrometer and the software for controlling the measurements were completed in Debrecen. It is used to measure the energy and angular distribution of electrons ejected from solid samples. First the plasmon excitation in amorphous silicon by electron impact was investigated

High-Resolution Measurements of e++ H2 O Total Cross Section

Using a purely electrostatic positron beam, the total cross section of positrons scattering from H2O has been measured for the first time with a high angular discrimination (≃1°) against forward scattered projectiles. Results are presented in the energy range (10-300) eV. Significant deviations from previous measurements are found which are, if ascribed entirely to the angular acceptances of various experimental systems, in quantitative accord with ab initio theoretical predictions of the differential elastic scattering cross section. © 2016 American Physical Society

An electrostatic brightness-enhanced timed positron beam for atomic collision experiments

An electrostatic positron beam, incorporating a remoderation stage to yield brightness enhancement with time-of-flight capabilities, has been developed and characterized. The beam is tunable in an energy range (5–500) eV with an angular divergence of ≃ 1° and an energy resolution of ≲ 1%

Strong projectile-energy dependence of the Auger-line intensity at 0° due to Coulomb focusing in fast proton-neon collisions

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Angular distribution and energy spectra of photoelectrons from tetrahydrofuran illuminated by VUV photon source

International audiencePhotoelectron emission from the valence shell of biologically relevant tetrahydrofuran (THF) molecule is studied. Energy and angular distributions of photoelectrons from THF ionized by a He(I) vacuum ultraviolet (VUV) photon source are measured. Theoretical calculations performed for the binding energies of orbitals and photoelectron intensities are in reasonable agreement with measurement. The observed angular distributions show the determining role of dipole transition mechanism

Comparison of the perioperative time courses of matrix metalloproteinase-9 (MMP-9) and its inhibitor (TIMP-1) during carotid artery stenting (CAS) and carotid endarterectomy (CEA)

Abstract Background Our aim was to compare the perioperative time courses of matrix metalloproteinase-9 (MMP-9) and its inhibitor (TIMP-1) in during carotid endarterectomy (CEA) and carotid artery stenting (CAS). Methods In our prospective study, twenty-five patients who were scheduled to undergo CAS were enrolled. We used a matched, historical CEA group as controls. Blood samples were collected at four time points: T1: preoperative; T2: 60 min after stent insertion; T3: first postoperative morning; and T4: third postoperative morning. Plasma MMP-9 and TIMP-1 levels were measured by ELISA. Results In the CEA group, the plasma levels of MMP-9 were significantly elevated at T3 compared to T1. In the CAS group, there was no significant difference in MMP-9 levels in the perioperative period. MMP-9 levels were significantly higher in the T3 samples of the CEA group compared to the CAS group. Significantly lower TIMP-1 levels were measured in both groups at T2 than at T1 in both groups. MMP-9/TIMP-1 at T3 was significantly higher than that at T1 in the CEA group compared to both T1 and the CAS group. Conclusions CAS triggers smaller changes in the MMP-9-TIMP-1 system during the perioperative period, which may correlate with a lower incidence of central nervous system complications. Additional studies as well as cognitive and functional surveys are warranted to determine the clinical relevance of our findings. Trial registration NIH U.S. National Library of Medicine, Clinicaltrials.gov,NCT03410576, 24.01.2018, Retrospectively registere

A method for intensity calibration of an electron spectrometer with multi-angle detection

A special electrostatic electron spectrometer designed for precise and unique experiments and an inten- sity calibration method for universal application in electron spectroscopy are presented. The upgrade of the analyzer enables the intensity calibration at arbitrary electron energies using elastically scattered electrons. In order to test the calibration procedure the double differential (in energy and angle) ioniza- tion cross sections (DDCS) of electrons ejected from 300 keV proton-argon collisions were measured and compared with the data of Rudd et al. [1]. The good agreement between the two data sets verifies the applicability of the calibration method