S. Ricz

Identification and angular distribution of the KL-LL2,3L2,3 satellites in the Ne K Auger spectra from the 5.5 MeV u-1 Ne3+-Ne collision process

The angular distributions of the KL-LL2,3L2,3 satellite transitions were measured in the 5.5 MeV u-1 Ne-Ne collision. A definite non-isotropic angular distribution was found for the satellite transitions 125pp(3P-2P), 125pp(1P-2P) and 125pp(1P-2D), as well as for the sum of the 125pp(3P-2D) and 116(3S-2D) transitions, while an isotropic angular distribution was found to characterise the 116pp(1S-2D) transition.

Kα/Kβ X-ray intensity ratios and K-shell ionisation cross sections for bombardment by electrons of 300-600 keV

The Kalpha /Kbeta intensity ratios were measured for X-rays from Fe, Co, Ni, Cu, Se and Y produced by electrons of 300-600 keV by using a Cockcroft-Walton accelerator. Absolute K-shell ionisation cross sections were also determined for Cu and Se.

A study of the angular distribution of the electrons in the peak near υe=υi in the electron spectra from He+-Ar and H2+-Ar collisions

The peak near ve=vi in the electron spectra from He+ (0.8 MeV amu-1), H2+ (0.8 MeV amu-1 and 1.995 MeV amu-1)-Ar collisions was studied at thirteen angles from 0 to 180 degrees . The experimental values for the positions and half widths (FWHM) of these peaks were compared with theoretical calculations. An example is given for the comparison of the actual shapes of the peak for different projectiles with the corresponding theoretical curves. The angular distribution of the electrons in the electron-loss peak (i.e. the single differential cross sections) was plotted together with the theoretical ones.

A simple theoretical approach to multiple ionization and its application for 5.1 and 5.5 MeV/u Xq++ Ne collisions

The simple geometrical model we developed recently for ionization probabilities on the basis of a geometrical BEA picture is generalized and extended to take into account magnetic substates and non-zero impact parameter ion-atom collisions. Ionization probabilities per electron for the L shell and separately for the 2s and 2p Subshells of neon in 5.1 MeV/u N+ and N7+ as well as 5.5 MeV/u H+ collisions were determined from 0.8−1 eV resolution K-Auger spectra. Anisotropy parameters of KL-LL23L23 satellite lines were determined in 5.5 MeV/u Ar6+, Ne10+ and 5.1 MeV/u N2+ collisions. The comparison of the extended model with the experimental data shows a good agreement. The model seems to be able to give account of the dependence of the ionization probability on quantum numbers l and m. Comparing the results with a wide range of experimental data no contradictions were found with the universal scaling features predicted by the model. By analyzing the impact parameter dependence of ionization probabilities the validity of the model was estimated to break down at ν1 ≈ ν2/3 towards lower impact velocities.

Observation of electron impact inner-shell excitation of argon by means of satellite Auger spectra

We have studied the inner-shell excited states of argon below the 2p thresholds for electron-impact excitation in the range of the incident energy . We carried this out through the measurement of the electrons emitted during the decay of the states. The corresponding satellite peaks in the spectra of the emitted electrons were separated from the normal (diagram) LMM Auger peaks by a special evaluating process. We observed the satellite peaks coming from the , and transitions at all applied incident energies. The intensity of the satellite peaks increased approaching the ionization threshold (). Nevertheless in the range - 1700 eV we could identify more satellites due to the lower continuous background and the smaller post-collision interaction effects.

Photoionization of Ne Atoms and Ne+ Ions Near the K Edge: PrecisionSpectroscopy and Absolute Cross-sections

Author(s): Muller, A; Bernhardt, D; Borovik, A; Buhr, T; Hellhund, J; Holste, K; Kilcoyne, ALD; Klumpp, S; Martins, M; Ricz, S; Seltmann, J; Viefhaus, J; Schippers, S | Abstract:

Recombination of U28+ ions in a dense, cold electron target

Abstract Recombination of highly charged ions with free electrons is studied in single-pass merged-beams experiments at the UNILAC accelerator of GSI. Specific features of the experimental setup are the high electron density (up to 10 10 cm −3 ) and the high magnetic field (up to 1 T) in the electron target, which exceed the corresponding numbers for typical electron coolers in storage rings by nearly two orders of magnitude. This provides unique possibilities to study new effects in electron-ion recombination. A previous experiment with U 28+ ions has shown a large enhancement of the recombination rate at low center-of-mass energies, where the dominating contribution is expected from radiative recombination. The observed rates exceed theoretical calculations by more than an order of magnitude. For the clarification of this observation we extended the previous measurement up to a center-of-mass energy E = 450 eV, checking the possibility of fortuitous resonances of dielectronic recombination near zero center-of-mass energy. The analysis of Rydberg sequences in the observed spectrum of resonances does not suggest the presence of DR at E = 0.

Prominent role of multielectron processes in K-shell double and triple photodetachment of oxygen anions.

The photon-ion merged-beam technique was used at a synchrotron light source for measuring the absolute cross sections of the double and triple photodetachment of O- ions. The experimental photon energy range of 524-543 eV comprised the threshold for K-shell ionization. Using resolving powers of up to 13 000, the position, strength, and width of the below-threshold 1s2s22p6 S2 resonance as well as the positions of the 1s2s22p5 P3 and 1s2s22p5 P1 thresholds for K-shell ionization were determined with high precision. In addition, systematically enlarged multiconfiguration Dirac-Fock calculations have been performed for the resonant detachment cross sections. Results from these ab initio computations agree very well with the measurements for the widths and branching fractions for double and triple detachment, if double shakeup (and shakedown) of the valence electrons and the rearrangement of the electron density is taken into account. For the absolute cross sections, however, a previously found discrepancy between measurements and theory is confirmed.

High resolution carbon and oxygen K-LL Auger spectra of carbon dioxide

Abstract The proton excited carbon and oxygen K–LL Auger spectra of carbon dioxide were measured using the high-resolution, angular resolving ESA-21 electron spectrometer. The proton impact energy was 1.0 MeV. The transition energies of both K–LL Auger-spectra (oxygen and carbon) are determined and compared with the existing theoretical and earlier experimental data. The experimental line widths full width at half maximum (FWHM) and relative intensities of the Auger lines are determined. The Auger emission was found to be isotropic within the experimental accuracy.

Auger electron spectra in 5.5 MeV amu-q Neq+ and Arq+ ion impact on Ne

A study of the Ne K Auger spectra induced by 5.5 MeV amu-1 Ne3+, Ne10+, Ar6+ and Ar17+ heavy ions on Ne is presented. Some average quantities (the centroid energy of the KLL Auger spectra, the average number of L vacancies produced simultaneously with the K vacancy, the effective charge of the projectile in the actual process, the satellite to total intensity ratio) characterising the KLn ionisation process have been extracted from these spectra. Relative K-shell ionisation cross sections and KLM and KLL cross section ratios have also been evaluated. The deduced experimental Zeff values have been compared with the results of PWBA and BEA calculations. A simple model calculation is made in an attempt to interpret the variation of the probability for the ejection of an L-shell electron (pL) as a function of Zeff/vp. Some statements regarding individual lines and groups in the Auger spectra are made.