Early interest in forbidden transitions from metastable states of hydrogen as, for instance, two-photon transitions, came mainly from astrophysics, and was recently reviewed by Chluba and Sunyaev [1]. The recent studies of forbidden transitions led to many practical applications. For example, the determination of the Rydberg constant, the measurement of the Lamb shift, the test of Bell’s inequality, the calibration of solid-state X-ray detectors, and the study of parity-violation effects in H-like and He-like ions, as well as various applications in molecular spectroscopy, tissue imaging, and protein structure analysis (we refer to Ref. [2] and references therein).

The objective of this project is the experimental and theoretical study of forbidden one- and two-photons transitions in atomic systems. Emphasis will be given to highly charged systems (calculations and high-precision measurements), to super-heavy atoms, and to atomic systems in super-critical fields.

This work will provide, among others, needed data for the interpretation of spectra from astrophysics and from  high accuracy experiments in atomic physics, namely from ECRIS (Electron Cyclotron Resonance Ion Source) plasmas, EBIT (Electron Beam Ion Traps ) plasmas, XUV-free electron laser (FALSH) produced plasmas, and tokamaks plasmas.

The main theoretical aim of this project is the calculation of forbidden transition decay rates of multielectronic systems, with relative accuracy of 10^-6, for different several states of selected ions in several charge states, and the development of a model to analyze and interpret high-resolution spectra emitted by the ions in different charge states in several types of plasmas.

The experimental aim of this project is the implementation of a spectrometer with double-crystal plane on the ECRIS (Electron Cyclotron Resonance Ion Source) ion source SIMPA (Multicharged Ion Source of Paris) at the Laboratoire Kastler Brossel (Ecole Normale Supérieur, Univ. Pierre and Marie Curie and CNRS), 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). To estimate the electron density and temperature in the plasma, it is also planned to conduct a theoretical study of the most important processes conducting to the creation of the excited states that will lead to the X-ray emission (transitions K) by the plasma ions.

This project is included in the long term European project SPARC (Stored Particles Atomic Physics Research Collaboration) [3]. The SPARC project involves studies of extreme atomic conditions using highly-charged very-heavy ions over a large energy range, from rest to the relativistic regime, in the accelerator FAIR (Facility for Antriprotons and Ions Research), which will be operational by 2012. This paves the experimental and theoretical background for the start of this new equipment, which will be the most efficient in the world.

[1] J. Chluba and R. A. Sunyaev, Astron. Astrophys. 480, 629 (2008).
[2] P. Amaro, J. P. Santos, F. Parente, A. Surzhykov, and P. Indelicato, Phys. Rev. A 79, 062504 (2009).
[3] SPARC. Stored Particles Atomic Physics Research Collaboration. Available from: http://www.gsi.de/fair/experiments/sparc/.