REVIEW OF ELECTRIC AND MAGNETIC CONFIGURATION-MIXING EFFECTS IN ATOMIC SPECTRA

Les résultats surprenants des études expérimentales et théoriques récentes concernant l'effet de champs électriques et magnétiques sur les spectres atomiques sont examinés. Nous nous intéresserons tout particulièrement aux structures qui existent dans le continuum de photoionisation et aux processus qui en sont la cause. Des exemples des conséquences du mélange de l'effet Paschen-Back et du diamagnétisme (a) et de l'autoionisation forcée (b) seront présentés.The surprising results of recent and current experimental and interpretive work on electric and magnetic field effects in atomic spectra are reviewed, with emphasis on processes responsible for spectral structures in regions of photoionization continua. Cases of (a) mixture of Partial Paschen-Back structure and Diamagnetic Shift, and (b) of "Forced autoionization" are presented

MAGNETIC ROTATION SPECTROSCOPY WITH SYNCHROTRON RADIATION

Nous décrivons des expériences récentes où la polarisation linéaire du rayonnement synchrotron dans le plan de l'orbite a été exploitée pour étudier les effets combinés de la biréfringence magnétique circulaire (effet Faraday) et du dichroisme magnétique circulaire (MCD) dans l'ultraviolet. A l'heure actuelle, nos études portent sur les séries principales des alcalino-terreux dans des champs magnétiques allant jusqu'à 4,6 Tesla. Nous avons pu observer des oscillations d'inténsité dues à l'effet Faraday jusqu'à n=28 environ. Au-dessus de cette valeur, les structures supplémentaires dues au mélange de 1 en champ intense compliquent l'inteprétation du phénomène. A partir de nos mesures, nous avons pu, par une méthode nouvelle, déduire les forces d'oscillateur relatives des transitions atomiques avec une précision qui va jusqu'a + - 0,25%, et qui dépasse donc largement celle des meilleures déterminations antérieures. Notre méthode offre aussi, du moins en principe, l'avantage de permettre l'étude des perturbations de la force d 'oscillateur en présence d'un champ magnétique intense. Enfin, elle ne nécessite qu'une optique réfléchissante et peut donc être utilisée dans l'ultraviolet lointain.We describe recent experiments in which the linear polarisation of synchrotron radiation in the orbital plane has been exploited to study the combined effects of magnetic circular birefringence (Faraday rotation) and magnetic circular dichroism (MCD) in the ultraviolet. To date, our experiments have concentrated on the principal series of alkaline-earths in magnetic fields of up to 4.6 Tesla. We have observed intensity oscillations due to Faraday rotation up to about n=28. Above this value, additional structures due to 1-mixing in high fields complicate the interpretation of the patterns. From our measurements, we have been able to deduce relative oscillator strengths of atomic transitions by a novel technique. The precision of these determinations can be as high as + - 0.25% in favourable cases, and is thus considerably higher than in earlier measurements using different techniques. Also, the present method has the advantage that, in principle, one could investigate perturbations of the f-value by intense magnetic fields. Finally, it requires only reflecting optics and can therefore be used in the vacuum ultraviolet

Analysis of autoionization resonances in the Hg 6s2-photoionization by measurements of photoelectron polarization

Schäfers F, Schönhense G, Heinzmann U. Analysis of autoionization resonances in the Hg 6s2-photoionization by measurements of photoelectron polarization. Zeitschrift für Physik A: Hadrons and Nuclei. 1982;304(1):41-48.Measurements of the spin polarization of photoelectrons in the autoionization region of the Hg 6s2-subshell using circularly polarized synchrotron radiation and using unpolarized light from rare gas discharge lamps are reported. The results obtained show a pronounced structure across the resonances. Together with data of the cross section and its angular distribution these data from a complete parameter set for the determination of the transition matrix elements and the phase difference of the continuum wavefunctions. Evidences for strong configuration interaction and channel mixing between the open and closed channels were found. The matrix elements and their ratio vary strongly across the resonances and the relative phase shows some changes of sign. A change of the relative phase by Pi across an autoionization resonance, predicted by Fano, has been verified experimentally for the triplet resonance. We would like to express our gratitude to Professors W. Paul, G. Nöldeke and J. Kessler for their continued interest and encouragement. We thank Dr. D. Husmann, Dr. J. Hormes and B. Osterheld for their assistance in performing the experiment in Bonn. We are grateful to Dr. N.A. Cherepkov for helpful discussions and acknowledge support by the DFG and BMFT