We present theoretical results for the photoabsorption spectrum of an atom in parallel electric and magnetic fields, using the R-matrix method combined with quantum-defect theory. We introduce a radial basis set which is complete and orthonormal over a semi-infinite interval [r0,(infinity)), to allow calculations to be performed for high Rydberg states in nonhydrogenic atoms without encountering problems due to linear dependence of the basis set. The nonhydrogenic character of the spectra is analyzed for Li and Rb, and a comparison is made with previous high-precision experiments which shows that the theoretical results agree very well with experiment.
We study the contribution of the most important processes leading to the creation of excited states of Cl14+ ions from the ground configurations of Cl ions in an Electron Cyclotron Resonance Ion Source (ECRIS), which lead to the emission of K X-ray lines. Theoretical values for inner-shell excitation, K and KL ionization cross-sections, and energies and transition probabilities for the de-excitation processes are calculated in the framework of the Multi-Configuration Dirac-Fock (MCDF) method. With reasonable assumptions about the electron energy distribution, a theoretical K[alpha] X-ray spectrum is obtained, which reproduces closely a recent experimental result.
The transition probabilities of Kα hypersatellite lines and energy shifts with respect to the corresponding diagram lines are computed using the Dirac–Fock model for several values of atomic number <I>Z</I> throughout the periodic table. The influence of the Breit interaction on the Kα<SUB>1</SUB><SUP>h</SUP>/Kα<SUB>2</SUB><SUP>h</SUP> line intensity ratio, Kα<SUB>1</SUB><SUP>h</SUP> and Kα<SUB>2</SUB><SUP>h</SUP> line energy shifts and Kα<SUB>1</SUB><SUP>h</SUP> to Kα<SUB>2</SUB><SUP>h</SUP> line energy splitting is evaluated. Double-K shell hole threshold values for selected elements with 23 ⩽<I>Z</I>⩽ 30, calculated within the same approach, are compared with available experimental results.
X-ray intensity ratios, such as the Kα2/Kα1 ratio, are parameters with a large application in atomic physics and related scientific and technological areas. D.
There is a need for reliable theoretical methods to calculate electron-impact total ionization cross sections for the large number of neutral atoms and ions with open shell structures. These cross sections are used in a wide range of scientific and industrial applications, such as astrophysical plasmas, atmospheric science, X-ray lasers, magnetic fusion, radiation physics, semiconductor fabrication, accelerator physics and tumor therapy physics. The binary-encounter-Bethe (BEB) model [1], using an analytic formula that requires only two atomic constants, the binding energy and kinetic energy of the electrons, generates direct ionization cross sections for any neutral atom (or molecule), which are reliable in intensity (15%) and shape from the ionization threshold to a few keV in the incident energy [3], or to thousands keV if we consider its relativistic version(RBEB) [2]. In this work we present K- and L-shell ionization cross sections calculations for heavy atoms.
Benzyl azide and the three methylbenzyl azides were synthesized and characterized by mass spectrometry (MS) and ultraviolet photoelectron spectroscopy (UVPES). The electron ionization fragmentation mechanisms for benzyl azide and their methyl derivatives were studied by accurate mass measurements and linked scans at constant B/E. For benzyl azide, in order to clarify the fragmentation mechanism, labelling experiments were performed. From the mass analysis of methylbenzyl azides isomers it was possible to differentiate the isomers ortho, meta and para. The abundance and nature of the ions resulting from the molecular ion fragmentation, for the three distinct isomers of substituted benzyl azides, were rationalized in terms of the electronic properties of the substituent. Concerning the para-isomer, IRC calculations were performed at UHF/6-31G(d) level. The photoionization study of benzyl azide, with He(I) radiation, revealed five bands in the 8-21 eV ionization energies region. From every photoelectron spectrum of methylbenzyl azides isomers it has been identified seven bands, on the same range as the benzyl azide. Interpretation of the photoelectron spectra was accomplished applying Koopmans' theorem to the SCF orbital energies obtained at HF/6-311++G(d, p) level.
Total electronic correlation corrections to the binding energies of the isoelectronic series of beryllium, neon, magnesium and argon, are calculated in the framework of relativistic multiconfiguration Dirac-Fock method. Convergence of the correlation energies is studied as the active set of orbitals is increased. The Breit interaction is treated fully self-consistently. The final results can be used in the accurately determination of atomic masses from highly charged ions data obtained in Penning-trap experiments.
MSc dissertation: Construção de um sismógrafo (modelo de Lehman) School: Universidade Nova de Lisboa Period: October 2004 – September 2005 Supervisor Co-Supervisor: I. Catarino
MSc theme: Estudo da concentração elementar em tecidos cancerígenos School: Universidade Nova de Lisboa Period: October 2015 – November 2016 Co-Supervisor
MSc theme: Estudo da concentração elementar em tecidos cancerígenos School: Universidade Nova de Lisboa Period: October 2015 – November 2016 Co-Supervisor
MSc theme: Determinação da concentração de mercúrio, e outros elementos traço, em tecidos dos peixes-zebra (Danio-Rerio) School: Universidade Nova de Lisboa Period: October 2015 – November 2016 Co-Supervisor
MSc theme: Desenvolvimento de um espectrómetro estado-da-arte, de fluorescência de raios-X dispersivo em energia com geometria triaxial School: Universidade Nova de Lisboa Period: October 2015 – May 2017 Co-Supervisor
