| | | Document Type | : | Latin Dissertation | | Language of Document | : | English | | Record Number | : | 53711 | | Doc. No | : | TL23665 | | Call number | : | 3461775 | | Main Entry | : | Yuri Paskover | | Title & Author | : | Single-Shot Time Resolved Four Wave Mixing SpectroscopyYuri Paskover | | College | : | The Weizmann Institute of Science (Israel) | | Date | : | 2008 | | Degree | : | Ph.D. | | student score | : | 2008 | | Page No | : | 75 | | Abstract | : | This thesis describes development of a novel technique of single shot time resolved four wave mixing spectroscopy. The technique is based on geometrical mapping of temporal delays between ultrashort pulses onto geometrical axes of the region of intersection between broad beams, followed by imaging of the emitted signal onto a CCD camera. The method allows for rapid time resolved measurement of molecular vibrational dynamics, reducing the experimental time down to the single pulse limit. Several experimental applications of this method are provided, demonstrating capabilities for the retrieval of vibrational spectra of molecules, and their assignment to specific modes and symmetry representations. The unique geometrical conditions of our setup imply strict phasematching constraints on the generation of the nonlinear signal. This strict phasematching plays a role of a spectral filter inherently applied to the emitted signal. The transmittance of this spectral filter may be tuned over the entire range of the signal's spectrum, allowing for separate detection of particular frequency sections of the nonlinear signal, leading to the observation of specific pathways of vibrational coherence in the molecule. Moreover, it is demonstrated both theoretically and experimentally, that a simple measurement of time resolved signal is insufficient for attributing the observed spectral peaks to molecular degrees of freedom. Generally, either mixing of the signal with an additional field for heterodyne measurement, or projection of the retrieved spectra on two frequency axes are required in order to assign the observed spectral feature to particular coherences excited in the molecule. Both these methods of assignment are implemented in this work in experimentally simple and convenient way. Finally, we have implemented our newly developed technique for measurements of the vibrational evolution of the molecule upon two electronic states. Two time delays between pulses were mapped onto the same image, providing a two dimensional map of molecular evolution. The retrieved data can be analyzed to provide information on coherent nuclear motion on both the ground and the excited electronic state potentials. | | Subject | : | Pure sciences; Molecular vibrational dynamics; Spectroscopy; Ultrashort pulses; Analytical chemistry; Molecular physics; 0486:Analytical chemistry; 0609:Molecular physics | | Added Entry | : | Y. A. Prior, Ilya | | Added Entry | : | The Weizmann Institute of Science (Israel) |
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