Multiphoton Ionization as Time-Dependent Tunneling

A new semiclassical approach to ionization by an oscillating field is presented. For a delta-function atom, an asymptotic analysis is performed with respect to a quantity h, defined as the ratio of photon energy to ponderomotive energy. This h appears formally equivalent to Planck's constant in a suitably transformed Schroedinger equation and allows semiclassical methods to be applicable. Systematically, a picture of tunneling wave packets in complex time is developped, which by interference account for the typical ponderomotive features of ionization curves. These analytical results are then compared to numerical simulations and are shown to be in good agreement.Comment: 36 pages (also printable half size), uuencoded compressed tarred Latex file with 9 Postscript figures included automaticall

Resonant Structures in the Low-Energy Electron Continuum for Single Ionization of Atoms in the Tunneling Regime

We present results of high-resolution experiments on single ionization of He, Ne and Ar by ultra-short (25 fs, 6 fs) 795 nm laser pulses at intensities 0.15-2.0x10^15 W/cm^2. We show that the ATI-like pattern can survive deep in the tunneling regime and that the atomic structure plays an important role in the formation of the low-energy photoelectron spectra even at high intensities. The absence of ponderomotive shifts, the splitting of the peaks and their degeneration for few-cycle pulses indicate that the observed structures originate from a resonant process.Comment: 11 pages, 3 figure

Pilotstudie Radarbefliegung der Unteren Mittelelbe

Multifrequente und multipolarisierte E-SAR Flugzeugradardaten wurden mit verschiedenen Klassifizierungsverfahren und einer Hauptkomponentenanalyse zu thematischen Karten der Landoberflächen und Vegetationstypen des Elbauen- und Rückdeichungsbereiches verarbeitet. Erste Modellanwendungen verschiedener Radarrückstreumodelle habe zu Hinweisen auf die Bodenfeuchte und Oberflächenrauhigkeit geführt

Pilotstudie Radarbefliegung

Erste Ergebnisse des Pilotprojektes Radarbefliegung im BMBF-Verbundprojekt "Morphodynamik der Elbe" Zwischenbericht über Geländekampagne, Radarbefliegung, Laborarbeiten und erste Datenauswertungen

Determination of Hydrological Parameters Using Multi-Frequency and Polarisation Airborne-Radar Data (E-SAR)

The aim of this project is to investigate the use of microwave remote sensing for the determination of hydrological parameters. Themost important parameter for modelling flood-plain inundatin is hydrological roughness and soil moisture. During the E-SAR mission, ground data have been collected over five test areas with heterogeneous surface structures from bare soil, low and high vegetation and shrubs and trees