Electron recombination with multicharged ions via chaotic many-electron states

We show that a dense spectrum of chaotic multiply-excited eigenstates can play a major role in collision processes involving many-electron multicharged ions. A statistical theory based on chaotic properties of the eigenstates enables one to obtain relevant energy-averaged cross sections in terms of sums over single-electron orbitals. Our calculation of the low-energy electron recombination of Au$^{25+}$ shows that the resonant process is 200 times more intense than direct radiative recombination, which explains the recent experimental results of Hoffknecht {\em et al.} [J. Phys. B {\bf 31}, 2415 (1998)].Comment: 9 pages, including 1 figure, REVTe

Formalism of collective electron excitations in fullerenes

We present a detailed formalism for the description of collective electron excitations in fullerenes in the process of the electron inelastic scattering. Considering the system as a spherical shell of a finite width, we show that the differential cross section is defined by three plasmon excitations, namely two coupled modes of the surface plasmon and the volume plasmon. The interplay of the three plasmons appears due to the electron diffraction of the fullerene shell. Plasmon modes of different angular momenta provide dominating contributions to the differential cross section depending on the transferred momentum.Comment: 11 pages, 2 figures; submitted to the special issue "Atomic Cluster Collisions: Structure and Dynamics from the Nuclear to the Biological Scale" of Eur. Phys. J.

Asymmetry sum rule for molecular predissociation

© 2000 American Physical SocietyIn the case of weak diatomic molecular predissociation by noninteracting, optically inactive continuum states, it is demonstrated that the predissociation line shape is more accurately represented by a Beutler-Fano profile than by a Lorentzian. The weak asymmetry that is found to occur is due principally to interactions with neighboring vibrational resonances. For this type of predissociation in the case of multiple continua, a sum rule for the corresponding line-shape asymmetry is derived. This sum rule is verified numerically using single-channel and multichannel coupled Schrödinger-equation calculations for the Schumann-Runge band system of O2. Similar results are presented for the case of optically active continua.F. T. Hawes, L. W. Torop, B. R. Lewis and S. T. Gibso

SOFT X-RAY SCATTERING IN THE VICINITY OF THE 3d ABSORPTION EDGES OF Ce IN CeO2

Le spectre de diffusion X de CeO2 au voisinage des seuils 3d du Ce presente des structures intenses qul sont situées à une energie légèrement plus élevée que celle des raies correspondantes du spectre de photoabsorption. On discute l'origine de ces structures à la lumiere d'un modèle de potential à double puits.The soft X-ray scattering spectrum of CeO2 in the vicinity of the 3d absorption edges of Ce show intense new features appearing above the positions of the main lines of the corresponding absorption spectrum. The origin of these features is discussed in the light of a double well potential model

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

The theoretical discussion of strong laser field effects: Intense, short pulses interacting with atoms and molecules

SIGLEAvailable from TIB Hannover: RO 5080(92-02) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman