E-Locus - Institutional Repository of the University of Crete

Home Collections Type of Work Doctoral theses

Doctoral theses

Search command : Author="Ραϊσάκη" And Author="Μαρία"

Current Record: 1 of 2453

[Add to Basket]

Identifier

000465980

Title

Excitation of heliumlike C4+ and O6+ projectile ions in collisions with He targets

Alternative Title

Μελέτη ατομικών διεγέρσεων δέσμης ηλιοειδών ιόντων C4+ και O6+ σε κρούσεις με στόχους He

Author

Λαουτάρης, Άγγελος Δ.

Thesis advisor

Τζούρος, Θεόδωρος

Reviewer

Μπενής, Εμμανουήλ
Λαγογιάννης, Αναστάσιος
Ρακιτζής, Πέτρος
Κομίνης, Ιωάννης
Αντύπας, Διονύσης
Dubois, Alain

Abstract

Using the APAPES (Atomic Physics with Accelerators: Projectile Electron Spectroscopy) project zero-degree Auger projectile spectrograph setup and the C⁴⁺ and O⁶⁺ He-like ion beams supplied by the 5.5 MV “Demokritos” tandem Van de Graaff accelerator, K-Auger projectile electron spectra measurements were performed, for 0.5-1.5 MeV/u collisions with He gas targets. He-like beams in general contain a mixture of 1s²¹S, 1s2s 1S ¹S and 1s2s ³S components, so all three initial channels are considered. In particular, this work focuses on the following two collision processes: X^q+ (1s²) + He →X^{(q+1) +} (1s2p²²D) + He⁺(All) (Transfer-Excitation) (1) ↳X^q+ (1s²) + e^-_A(θ=0^ο) (2) and X^q+ (1s², 1s2s ^3,1S) + He →X^q+ (2s2p ^3.1P ) + He(All) (Projectile Excitation) (3) ↳ X^(q-1)+(1s) + e^-_A(θ=0^ο) (4) where X^q+refers to carbon C⁴⁺ or oxygen O⁶⁺ projectiles. The second line of each process indicates the emission of the Auger electron and its detection at theta=0 degrees. In this thesis, the cross section for the production of the 1s2p²²D, 2s2p ³P and 2s2p ¹P states were determined, in order to study the transfer-excitation (TE), single and double projectile excitation atomic processes. The measurements are also accompanied by close-coupling (CC) calculations in which three-active electrons have been included for the first time (3eAOCC) ¹, in an attempt to cast further light on these complex multi-electron processes. The calculated cross sections for the production of 1s2p²²D from 1s²¹S through TE, both for carbon and oxygen are found to be in agreement with zero-degree Auger projectile spectroscopy measurements covering the maximum of the resonance peak and its high energy wing. At lower energies, the theoretical results show a second maximum which is interpreted recently [1] through a nonresonant one-step transfer excitation mechanism. In the case of 2s2p ³P and 2s2p ¹P the 3eAOCC calculated cross sections were converted to Auger electron normalized yields for a direct comparison between theory and experiment, as 2s2p 3P and 2s2p ¹P states can be populated by all three 1s²¹S, 1s2s 1S ¹S and 1s2s ³S components through different processes. Although both theory and experiment trends appear to have a similar energy dependence, the theoretical results in this case are in general smaller than the experimental, leaving room for discussion on the possible reasons that this happens.

Language

English

Subject

Accelerator-based atomic physics

Auger electron spectroscopy

Doubly-excited states

Electron excitation

Electron transfer-excitation

He-like ions

Highly-charged ions

Ion-atom collisions

Li-like ions