Atomic Systems

Theoretical work

We will pursue the analysis and interpretation of high-resolution X-ray spectra emitted by several atomic systems, in various charge states, for laboratory and astrophysics plasma diagnostics purposes. These studies imply the calculation of atomic energy levels, transition energies, radiative and radiationless transition probabilities in a relativistic framework, as well as the development of a model to simulate the X-ray spectra [1-5].

We will continue the theoretical study of the two-photon transitions in collaboration with the French and German research groups, for atomic systems with one-, two-, and three-electrons [6-7].

New models that produce reliable electron impact ionization cross-sections for neutral atoms, based in the BEB and RBEB expressions, in non-relativistic and relativistic framework, respectively, are under development. These new MBEB and MRBEB models require only one atomic parameter, namely the binding energy of the electrons to be ionized [8-10].
A code based in the Monte Carlo method has been developed to analyze the propagation of radiation through the human retina. Preliminary results show the possibility of developing a technique to detect druses inside the retina.

Experimental Work

The lead concentration in several tissues and organic fluids of rats exposed to lead has been investigated. Because of the different physical and chemical composition of the samples, we have been using energy dispersive X-ray fluorescence (EDXRF) and proton-induced X-ray emission (PIXE) techniques for measure lead concentration in solid samples and the Electrothermal Atomic Absorption (ETAAS) technique to determine the lead concentration in liquid samples.

The existing collaboration in the implementation of a spectrometer with double-crystal plane on the ECRIS (Electron Cyclotron Resonance Ion Source) ion source SIMPA at the Laboratoire Kastler Brossel (Paris), to study forbidden and allowed X-ray transitions by multiply charged ions (Ar, S, K and Ca) present in the plasma source, in order to measure their energies and line widths with unprecedented accuracy (~1 ppm), will continue.

References

1. J. Cederberg, L. Kang, C. Conklin, and E. Berger, Hyperfine spectrum of NaF. Journal of Molecular Spectroscopy, 2010. 263(2): p. 142-144.
2. M.C. Martins, J.P. Marques, A.M. Costa, J.P. Santos, F. Parente, S. Schlesser, E.-O.L. Bigot, and P. Indelicato, Production and decay of sulfur excited species in an electron-cyclotron-resonance ion-source plasma. Physical Review A (Atomic, Molecular, and Optical Physics), 2009. 80(3): p. 032501.
3. A.M. Costa, M.C. Martins, J.P. Santos, P. Indelicato, and F. Parente, Relativistic calculation of K&alpha; hypersatellite line energies and transition probabilities for selected atoms with 12<=Z<=80. Journal of Physics B: Atomic, Molecular and Optical Physics, 2007. 40(1): p. 57.
4. G.C. Rodrigues, P. Indelicato, J.P. Santos, P. Patté, and F. Parente, Systematic calculation of total atomic energies of ground state configurations. Atomic Data and Nuclear Data Tables, 2004. 86(2): p. 117-233.
5. M.C. Martins, A.M. Costa, J.P. Santos, P. Indelicato, and F. Parente, Interpretation of X-ray spectra emitted by Ar ions in an ECR ion source. Journal of Physics B: Atomic and Molecular Physics, 2001. 34(4): p. 533-543.
6.  A. Surzhykov, A. Volotka, F. Fratini, J.P. Santos, P. Indelicato, G. Plunien, T. Stöhlker, and S. Fritzsche, Angular correlations in the two-photon decay of heliumlike heavy ions. Physical Review A, 2010. 81(4): p. 042510.
7. P. Amaro, J.P. Santos, F. Parente, A. Surzhykov, and P. Indelicato, Resonance effects on the two-photon emission from hydrogenic ions. Physical Review A (Atomic, Molecular, and Optical Physics), 2009. 79(6): p. 062504.
8. J.P. Santos, F. Parente, and Y.-K. Kim, Cross sections for K-shell ionization of atoms by electron impact. Journal of Physics B: Atomic and Molecular Physics, 2003. 36(21): p. 4211-4224.
9. Y.-K. Kim, J.P. Santos, and F. Parente, Extension of the binary-encounter-dipole model to relativistic incident electrons. Physical Review A, 2000. 62: p. 052710.
10. J.P. Santos and F. Parente, Ionisation of phosphorus, arsenic, antimony, and bismuth by electron impact. The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics, 2008. 47(3): p. 339-350.