@phdthesis{Steinbacher2015,
  author    = {Steinbacher, Andreas Edgar},
  title     = {Circular dichroism and accumulative polarimetry of chiral femtochemistry},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-116500},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2015},
  abstract  = {This work brings forward successful implementations of ultrafast chirality-sensitive spectroscopic techniques by probing circular dichroism (CD) or optical rotation dispersion (ORD). Furthermore, also first steps towards chiral quantum control, i.e., the selective variation of the chiral properties of molecules with the help of coherent light, are presented. In the case of CD probing, a setup capable of mirroring an arbitrary polarization state of an ultrashort laser pulse was developed. Hence, by passing a left-circularly polarized laser pulse through this setup a right-circularly polarized laser pulse is generated. These two pulse enantiomers can be utilized as probe pulses in a pump--probe CD experiment. Besides CD spectroscopy, it can be utilized for anisotropy or ellipsometry spectroscopy also. Within this thesis, the approach is used to elucidate the photochemistry of hemoglobin, the oxygen transporting protein in mammalian blood. The oxygen loss can be triggered with laser pulses as well, and the results of the time-resolved CD experiment suggest a cascade-like relaxation, probably through different spin states, of the metallo-porphyrins in hemoglobin. The ORD probing was realized via the combination of common-path optical heterodyne interferometric polarimetry and accumulative femtosecond spectroscopy. Within this setup, on the one hand the applicability of this approach for ultrafast studies was demonstrated explicitly. On the other hand, the discrimination between an achiral and a racemic solution without prior spatial separation was realized. This was achieved by inducing an enantiomeric excess via polarized femtosecond laser pulses and following its evolution with the developed polarimeter. Hence, chiral selectivity was already achieved with this method which can be turned into chiral control if the polarized laser pulses are optimized to steer an enhancement of the enantiomeric excess. Furthermore, within this thesis, theoretical prerequisites for anisotropy-free pump--probe experiments with arbitrary polarized laser pulses were derived. Due to the small magnitude of optical chirality-sensitve signals, these results are important for any pump--probe chiral spectroscopy, like the CD probing presented in this thesis. Moreover, since for chiral quantum control the variation of the molecular structure is necessary, the knowledge about rearrangement reactions triggered by photons is necessary. Hence, within this thesis the ultrafast Wolff rearrangement of an α-diazocarbonyl was investigated via ultrafast photofragment ion spectroscopy in the gas phase. Though the compound is not chiral, the knowledge about the exact reaction mechanism is beneficial for future studies of chiral compounds.},
  subject      = {Ultrakurzzeitspektroskopie},
  language  = {en}
}
@article{UllmannSchmittRothetal.2014,
  author    = {Ullmann, Tobias and Schmitt, Andreas and Roth, Achim and Duffe, Jason and Dech, Stefan and Hubberten, Hans-Wolfgang and Baumhauer, Roland},
  title     = {Land Cover Characterization and Classification of Arctic Tundra Environments by Means of Polarized Synthetic Aperture X- and C-Band Radar (PolSAR) and Landsat 8 Multispectral Imagery — Richards Island, Canada},
  doi       = {10.3390/rs6098565},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-113303},
  year      = {2014},
  abstract  = {In this work the potential of polarimetric Synthetic Aperture Radar (PolSAR) data of dual-polarized TerraSAR-X (HH/VV) and quad-polarized Radarsat-2 was examined in combination with multispectral Landsat 8 data for unsupervised and supervised classification of tundra land cover types of Richards Island, Canada. The classification accuracies as well as the backscatter and reflectance characteristics were analyzed using reference data collected during three field work campaigns and include in situ data and high resolution airborne photography. The optical data offered an acceptable initial accuracy for the land cover classification. The overall accuracy was increased by the combination of PolSAR and optical data and was up to 71\% for unsupervised (Landsat 8 and TerraSAR-X) and up to 87\% for supervised classification (Landsat 8 and Radarsat-2) for five tundra land cover types. The decomposition features of the dual and quad-polarized data showed a high sensitivity for the non-vegetated substrate (dominant surface scattering) and wetland vegetation (dominant double bounce and volume scattering). These classes had high potential to be automatically detected with unsupervised classification techniques.},
  language  = {en}
}