Relativistic Magnetic-Dipole Transitions in Atoms, Ions and Psions

Lev M Barkov, Max S. Zolotorev, D. A. Melik-Pashaev

Kunnat J. Sebastian

Chang-qi Cao, Xiaowei Fu, Hui W. Cao

A relativistic and non-Markovian study is carried out on the magnetic-dipole emission of a hydrogen-like atom of large atomic number Z without perturbation approximation. The correlation spectra are derived analytically and the corresponding correlation functions are calculated numerically. The Markovian approximation is seen to be satisfied with more accuracy as compared with the case of electric-dipole emission while the relativistic corrections are quite larger. In transition 2S1/2 to 1S1/2, the relativistic values even become several times of the non-relativistic values. As a comparison with the magnetic-dipole emission, the electric-quadrupole emission in the case of the 2D3/2 to 1S1/2 transition is also studied.

Roger Boudet

Pedro Manuel Duarte Gonçalves Amaro

One active topic in Atomic Physics is the study of highly charged ions (HCI). These physical systems have a strong Coulomb field that provides a unique opportunity to investigate and validate relativistic, Quantum ElectroDynamics (QED), and many-body e ects. Moreover, fundamental test on symmetries and parity violation gives clues to the physics beyond the Standard Model. Thus, nowadays, a primary goal of Atomic Physics is the existence of precise experimental data and accurate theoretical calculations for these systems. In this thesis I focus on the investigation of forbidden radiative transitions in HCI. The main emphasis of this work is on atomic transitions, in which the selection rules forbids the emission of electric dipole photons. In this special type of radiative transition, the electron decays mainly through the emission of a single magnetic dipole photon, or two electric dipole photons. Both types of decay are investigated either experimentally or theoretically. The two-photon decay is only theoretically investigated, using a full relativistic formalism,in HCI with one or two electrons. Several physical e ects in the two photon decay, such as resonances, the Dirac’s negative continuum or angular correlations are considered. Related with the decay, two-photon excitation is also investigated. According to these evaluations, I stress the importance of relativistic and nondipolar e ects. Moreover, a new approach based on the B-polynomials basis set is employed on two-photon transitions. The second part of the work is devoted to the precise measurement of transitions in highly charged Ar with two to four electrons. For that matter, I describe the technical features of a double crystal spectrometer used to perform those measurements in HCI for the first time. This kind of spectrometer is able to perform absolute and precise measurements with an accuracy never achieved in these systems, which enables a comparison with recent QED calculations. I describe a Monte-Carlo code developed with the purpose of studying several systematic errors, as well as testing the various methods of retrieving physical quantities from raw data. Finally, I present the first absolute 2 ppm measurements on HCI with this spectrometer, paying special attention on the forbidden magnetic dipole transition in He-like Ar.

Sinan Karaveli, Alexandra Witthoft, Rashid Zia

We present experimental evidence of optically enhanced magnetic dipole transitions from trivalent Europium ions. Spectra and lifetime data are used to highlight direct and indirect enhancement pathways, and implications for optical metamaterials are discussed.