3,958 research outputs found
Perturbation Approach to the Self Energy of non-S Hydrogenic States
We present results on the self-energy correction to the energy levels of
hydrogen and hydrogenlike ions. The self energy represents the largest QED
correction to the relativistic (Dirac-Coulomb) energy of a bound electron. We
focus on the perturbation expansion of the self energy of non-S states, and
provide estimates of the so-called A60 perturbative coefficient, which can be
considered as a relativistic Bethe logarithm. Precise values of A60 are given
for many P, D, F and G states, while estimates are given for other electronic
states. These results can be used in high-precision spectroscopy experiments in
hydrogen and hydrogenlike ions. They yield the best available estimate of the
self-energy correction of many atomic states.Comment: 18 pages (in 2-column format), 21 figures. Version 2 (June 20, 2003)
includes minor modification
Refining the Experimental Extraction of the Number of Independent Samples in a Mode-Stirred Reverberation Chamber
We investigate the number of independent samples in a chaotic reverberation
chamber. Its evaluation as defined by the IEC standard can be made more precise
when using not the index of the first value larger then the correlation length
but using the value obtained by a linear interpolation instead. The results are
validated by a juxtaposition with values from a measurement using a high
stirrer-angle resolution. A comparison with estimates known from the literature
validates our findings. An alternative approach using the local maxima of the
parametric dependence of the transmission is presented in order to show the
applicability of the extracted correlation length over a large range of
frequencies.Comment: 7 pages, 7 figure
Universal intensity statistics in a chaotic reverberation chamber to refine the criterion of statistical field uniformity
International audienceThis article presents a study of the intensity statistics of the electromagnetic response in a chaotic reverberation chamber (RC) in the presence of losses. Through an experimental investigation, intensity statistics of the response in a conventional mode-stirred RC are compared with those in a chaotic RC in the neighborhood of the Lowest Useable Frequency. The present work illustrates how the universal statistical properties of the field in an actual chaotic RC can ensure the validity of the standard criterion proposed to evaluate the uniformity of the field distribution. In particular, through a theoretical approach based on the random matrix theory applied to open chaotic systems, we find that the modal overlap seems to be the only relevant parameter of the corresponding intensity distribution
- …