Zwei- und Drei-Photonen Doppelionisation von Helium und Neon am Freie-Elektronen-Laser in Hamburg

Few-photon double ionization of helium and neon was investigated differentially at the free-electron laser at Hamburg (FLASH) with a reaction microscope. Both sequential and direct mechanism of few-photon double ionization were investigated. The specific temporal structure of the FLASH pulse sequence required the use of a new data aquisition system based on the digitization of analog signals. For the sequential few-photon double ionization the detection of all three emitted particles became possible for the first time. Thus one was able to gain detailed information about the reaction mechanisms and in particular identify the role of the electron-electron correlation