FU Berlin Digitale Dissertation
Oliver Dühr : Development and setup of a sub-50-fs-spectrometer for analysis of ultrafast molecular dynamics of chlorine dioxide and sulfur hexafluoride Entwicklung und Aufbau eines sub-50-fs-Spektrometers zur Untersuchung der ultraschnellen molekularen Dynamik von Chlordioxid und Schwefelhexafluorid
|Abstract| |Table of Contents| |More Information|

Abstract In this thesis the experimental results on ultrafast excitation of molecular structures (chlorine dioxide, sulfur hexafluoride) are presented. The core component of the setup is a 1 kHz 32 fs Ti:Sapphire based laser with 2.5 mJ energy based on chirped pulse amplification technique. 15 fs pulses are stretched by a factor of 10000 and energy enhanced by a chain of regenative and multipass amplification. Compression is done by a simple grating pair. The necessity of dispersion control of at least third order is discussed. The optimization of the System is carried out with the calculations of a ray-tracing program. For the experiments the pulse duration from the amplifier chain is not short enough. The next step is the spectral broadening of the pulses in dielectric hollow waveguides due to selfphasemodulation in an atomic gases. After compression with prisms and chirped mirrors, the duration of the pulses at 800 nm is 9 fs with more than 0.5 mJ energy. For the first time the compression at 400 nm with the same technique is presented. The duration of these pulses is 8 fs with 0.015 mJ energy. The problems of compression at 400 nm are discussed. Pump-probe experiments of chlorin dioxide in different solutions is presented. The molecule is pumped and probed with 400 nm, 50 fs pulses. The different behaviour in water, acetonitrile and cyclohexane shows the influence of the caging effect. The appearance of oscillations with 102 fs is in contradiction with gas-phase results. The difference to gas-phase experiments is discussed. The last chapter reports the impulsive excitation of raman active sulfur hexafuoride in the gas phase. The pulse duration (20 fs) is shorter then the molecular vibration mode (43 fs). The molecule acts as a single-mode raman oscillator without rotational modes. The established theoretical model predicts the generation of lower frequency components in the spectrum of the incident pulse due to impulsive raman excitation of the molecular vibration which is observed experimentally. The compression of the new wavelenghts shows a new method of generating tunable pulses with durations up to 16 fs over a wide range of the laser spectrum, since this process is independent from the incident wavelength.

Table of Contents Download the whole PhDthesis as a zip-tar file or as zip-File For download in PDF format click the chapter title Titelblatt und Inhaltsverzeichnis 1 Einleitung 1 2 Erzeugung kurzer Laserpulse 5 2.1 Eigenschaften kurzer Laserpulse 5 2.2 Dispersionskontrolle 8 2.3 Messmethoden der Ultrakurzzeitphysik 15 2.4 Ultrakurzpulsquellen 24 2.5 Verstärkung von fs-Laserpulsen 29 3 Impulsverkürzung 53 3.1 Spektrale Verbreiterung 53 4 fs-Dynamik von ClO2 89 4.1 Einführung 89 4.2 Photochemie von ClO2 90 4.3 ClO2-Synthese 94 4.4 Experimenteller Aufbau 95 4.5 Ergebnisse 100 4.6 Diskussion der Ergebnisse 103 5 Raman-Anregung auf der fs-Zeitskala 109 5.1 Grundlegendes zur Raman-Anregung 109 5.2 Impulsive Raman-Anregung von SF6 113 5.3 Diskussion der Ergebnisse 121 6 Zusammenfassung 127 Anhang 131 Literaturverzeichnis

More Information:
Online available:	http://www.diss.fu-berlin.de/1999/4/indexe.html
Language of PhDThesis:	german
Keywords:	chirped pulse amplification, hollow waveguide, impulsive raman scattering
DNB-Sachgruppe:	29 Physik, Astronomie
Classification PACS:	42.65
Date of disputation:	27-Jan-1999
PhDThesis from:	Fachbereich Physik, Freie Universität Berlin
First Referee:	Prof. Dr. Ingolf V. Hertel
Second Referee:	Prof. Dr. Dietmar Stehlik
Contact (Author):	duehr@mbi-berlin.de
Contact (Advisor):	korn@mbi-berlin.de
Date created:	29-Jan-1999
Date available:	01-Feb-1999

 

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