Femtosecond dynamics snapshots of the early ion track evolution

The energy dissipation and femtosecond dynamics due to fast heavy ions in matter is critically reviewed with emphasis on possible mechanisms that lead to materials modi cations. Starting from a discussion of the initial electronic energy deposition processes, three basic mechanisms for the conversion of electronic into atomic energy are investigated by means of Auger electron spectroscopy. Results for amorphous Si, amorphous C and polypropylene are presented and discussed. Experimental evidence for a highly charged track region as well as for hot electrons inside tracks is shown. As follows mainly from Auger electron spectroscopy, there are strong indications for di erent track production mechanisms in di erent material

Search for short time phase effects in the electronic damage evolution A case study with silicon

This work focusses on the production and decay properties of inner shell vacancies and valence band excitations induced by swift highly charged ions interacting with amorphous and crystalline Si. High resolution electron spectra have been taken for fast heavy ions at 1.78 5 MeV u as well as for electrons of similar velocity incident on atomically clean Si targets of well defined phase. Various Augerelectron structures are analyzed concerning their width, their intensity and exact peak position. All measured peaks show a small shift towards lower energy when the charge of the projectile is increased. This finding is an indication for a nuclear track potential inside the ion track. A detailed analysis of the Auger electron spectra for amorphous Si and crystalline Si 111 7 x 7 points to a small but significant phase effect in the short time dynamics of ion track

High energy ion beam irradiation of Co NiFe Co Cu multilayers Effects on the structural, transport and magnetic properties

The aim of this work is to investigate the effects of 593 MeVAu irradiation using two different projectile charges, namely Au30 and Au46.3 on the structural, transport and magnetization properties of Co NiFe Co Cu multilayers. X Ray diffraction and extended X ray absorption fine structures measurements show no significant structural change for as deposited and irradiated multilayers. On the other hand, the magnetoresistance amplitude decreases with the ion fluence but it is insensitive to the projectile charge state. The correlation between changes in the magnetoresistance and remanent magnetization suggests that the main effect responsible for the decrease of the magnetoresistance is the creation of ferromagnetic pinholes. These results are discussed on basis of the electronic thermal spike model and nuclear cascades theory and show similarities to the effects observed at low energy ion beam irradiatio

Evidence for phase formation in potassium intercalated 1,2;8,9-dibenzopentacene

We have prepared potassium intercalated 1,2;8,9-dibenzopentacene films under vacuum conditions. The evolution of the electronic excitation spectra upon potassium addition as measured using electron energy-loss spectroscopy clearly indicate the formation of particular doped phases with compositions K$_x$dibenzopentacene ($x$ = 1,2,3). Moreover, the stability of these phases as a function of temperature has been explored. Finally, the electronic excitation spectra also give insight into the electronic ground state of the potassium doped 1,2;8,9-dibenzopentacene films.Comment: 6 pages, 5 figures. arXiv admin note: text overlap with arXiv:1201.200

Ultrafast electronic processes in an insulator The Be and O sites in BeO

The short time dynamics of amorphous beryllium oxide a BeO has been investigated for electronic excitation ionization by fast incident electrons, as well as by Ar7 , Ar15 , Xe15 , and Xe31 ions at velocities of 6 10 the speed of light. Site specific Auger electron spectra induced by fast heavy ions are the central point of this investigation. Electron induced Auger spectra serve as a reference and electron energy loss EELS spectroscopy as well as resonant inelastic X ray scattering RIXS are invoked for quantitative understanding. For the heavy ion case, we observe strong variations in the corresponding spectral distributions of Be K and O K Auger lines. These are related to local changes of the electron density, of the electron temperature and even of the electronic band structure of BeO on a femtosecond time scale after the passage of highly charged heavy ions

Restoration of supersymmetric Slavnov-Taylor and Ward identities in presence of soft and spontaneous symmetry breaking

Supersymmetric Slavnov-Taylor and Ward identities are investigated in presence of soft and spontaneous symmetry breaking. We consider an abelian model where soft supersymmetry breaking yields a mass splitting between electron and selectron and triggers spontaneous symmetry breaking, and we derive corresponding identities that relate the electron and selectron masses with the Yukawa coupling. We demonstrate that the identities are valid in dimensional reduction and invalid in dimensional regularization and compute the necessary symmetry-restoring counterterms.Comment: 35 pages, LaTeX, 9 postscript figure

Radio detection of cosmic ray air showers with LOPES

In the last few years, radio detection of cosmic ray air showers has experienced a true renaissance, becoming manifest in a number of new experiments and simulation efforts. In particular, the LOPES project has successfully implemented modern interferometric methods to measure the radio emission from extensive air showers. LOPES has confirmed that the emission is coherent and of geomagnetic origin, as expected by the geosynchrotron mechanism, and has demonstrated that a large scale application of the radio technique has great potential to complement current measurements of ultra-high energy cosmic rays. We describe the current status, most recent results and open questions regarding radio detection of cosmic rays and give an overview of ongoing research and development for an application of the radio technique in the framework of the Pierre Auger Observatory.Comment: 8 pages; Proceedings of the CRIS2006 conference, Catania, Italy; to be published in Nuclear Physics B, Proceedings Supplement

Air Shower Measurements with the LOPES Radio Antenna Array

LOPES is set up at the location of the KASCADE-Grande extensive air shower experiment in Karlsruhe, Germany and aims to measure and investigate radio pulses from Extensive Air Showers. Since radio waves suffer very little attenuation, radio measurements allow the detection of very distant or highly inclined showers. These waves can be recorded day and night, and provide a bolometric measure of the leptonic shower component. LOPES is designed as a digital radio interferometer using high bandwidths and fast data processing and profits from the reconstructed air shower observables of KASCADE-Grande. The LOPES antennas are absolutely amplitude calibrated allowing to reconstruct the electric field strength which can be compared with predictions from detailed Monte Carlo simulations. We report about the analysis of correlations present in the radio signals measured by the LOPES 30 antenna array. Additionally, LOPES operates antennas of a different type (LOPES-STAR) which are optimized for an application at the Pierre Auger Observatory. Status, recent results of the data analysis and further perspectives of LOPES and the possible large scale application of this new detection technique are discussed.Comment: 8 pages, 10 figures, Contribution to the Arena 2008 conference, Rome, June 200