Search
Now showing items 141-150 of 333
Aufsatz
Detecting ultrafast interatomic electronic processes in media by fluorescence
(In: New journal of physics. - London : IOP, 2014, 16, 102002, 1-9, 2014)
Interatomic coulombic decay (ICD), a radiationless transition in weakly bonded systems, such as solutes or van der Waals bound aggregates, is an effective source for electrons of low kinetic energy. So far, the ICD processes could only be probed in ultra-high vacuum by using electron and/or ion spectroscopy. Here we show that resonant ICD processes can also be detected by measuring the subsequently emitted characteristic fluorescence radiation, which makes their study in dense media possible.
Dissertation
Many-body theory of laser-induced ultrafast demagnetization and angular momentum transfer in ferromagnetic transition metals
(2014-08-07)
An electronic theory is developed, which describes the ultrafast demagnetization in itinerant ferromagnets following the absorption of a femtosecond laser pulse. The present work intends to elucidate the microscopic physics of this ultrafast phenomenon by identifying its fundamental mechanisms. In particular, it aims to reveal the nature of the involved spin excitations and angular-momentum transfer between spin and lattice, which are still subjects of intensive debate. In the first preliminary part of the thesis the ...
Dissertation
Kohärente transiente und effiziente Endzustandskontrolle in Atomen und Molekülen
(2016-11-28)
Es ist ein lang gehegter Traum in der Chemie, den Ablauf einer chemischen Reaktion zu kontrollieren und das Aufbrechen und Bilden chemischer Bindungen zu steuern. Diesem Ziel verschreibt sich auch das Forschungsgebiet der Femtochemie. Hier werden Femtosekunden Laserpulse eingesetzt um auf dem Quantenlevel molekulare Dynamiken auf ihren intrinsischen Zeitskalen zu kontrollieren und das System selektiv und effizient von einem Anfangs- in einen Zielzustand zu überführen. Der Wunsch, mit geformten Femtosekunden Laserpulsen ...
Dissertation
Optimierung von Nanostrukturen in Dielektrika für biomedizinische und technische Applikationen durch zeitlich geformte Femtosekunden-Laserpulse
(2017-09-28)
Das Ablationsverhalten von Dielektrika wird in Abhängigkeit von unterschiedlich zeitlich geformten Femtosekunden-Laserpulsen analysiert. Dabei entstehen unterschiedlich tiefe Strukturen im Nano- und Mikrometerbereich. In zwei Anwendungsbeispielen wird deren Anwendbarkeit für biomedizinische und technische Applikationen beschrieben.
Dissertation
Laser amplification in excited dielectrics
(2018-02-12)
Today, laser processing of dielectric materials with ultrashort, femtosecond laser pulses finds a great variety of applications. While ablation, cutting or welding of different types of glasses are widespread and popular examples, nanostructuring of transparent crystals or optoporating cells is part of more recent scientific studies. Although the material systems seem to be very different, their interaction with visible and infrared wavelengths is very similar: the light is simply transmitted. This changes drastically ...
Dissertation
Methods of generating carrier-envelope-phase stabilized, intense, few-cycle laser pulses
(2015-02-12)
Ultrafast laser pulses have become an integral part of the toolbox of countless laboratories doing physics, chemistry, and biological research. The work presented here is motivated by a section in the ever-growing, interdisciplinary research towards understanding the fundamental workings of light-matter interactions. Specifically, attosecond pulses can be useful tools to obtain the desired insight. However access to, and the utility of, such pulses is dependent on the generation of intense, few-cycle, carrier-envelope-phase ...