@incollection {falkenroth2007a,
	title = {Visualisation of oxygen concentration fields in the mass boundary layer by fluorescence quenching},
	year = {2007},
	publisher = {Springer Verlag},
	abstract = {Laser-Induced Fluorescence (LIF) is applied to observe directly the mechanism of gas exchange in the aqueous viscous boundary layer at a free water surface. In order to make dissolved oxygen visible, a new class of fluorescent dyes is used with a life time in the order of microseconds so that the quenching constant for dissolved oxygen is sufficiently high for sensitive measurements. Depth profiles of the O2 concentration near the water surface are obtained by a vertical laser sheet at a rate of 185 frames per second. This technique is capable of a measurement sector up to several centimetres down from the water surface with a resolution in the order of 50-100 um. For a small circular wind/wave facility a correlation between wind speed and gas-exchange rates calculated from the extrapolated mean boundary-layer thickness are presented as well as the results of parallel measurements with a budget method for other gases with known Schmidt numbers.},
	doi = {10.1007/978-3-540-36906-6_4},
	author = {A. Falkenroth and Kai Degreif and Bernd J{\"a}hne and Bernd J{\"a}hne},
	editor = {Christoph S. Garbe and Handler, R. A.}
}
@phdthesis {falkenroth2007,
	title = {Visualisation of Oxygen Concentration Profiles in the Aqueous Boundary Layer},
	year = {2007},
	publisher = {Fakult{\"a}t f{\"u}r Chemie und Geowissenschaften, Univ.\ Heidelberg},
	abstract = {In environment studies as well as for technical application, the study of air-water gas exchange is crucial. For process studies, a novel visualisation technique of oxygen concentrations in water was realised with high spatial resolution. To resolve turbulent processes in water, also the temporal resolution was pushed to the limit of a imaging frame rate of 185 Hz. For this purpose, the well-established method of laser-induced fluorescence (LIF) was extended introducing in this type of studies a new phosphorescent ruthenium dye that is more than 15 times more sensitive to oxygen than the previously used indicator dye. The chemical synthesis of this metal-ligand complex MLC was adapted to a preparation without intermediate steps. The challenge of this imaging technique for small-scale interactions was to resolve a very thin boundary layer extending less than a millimetre below the water surface. An image processing algorithm was developed that allow the automatic detection of the exact location of the air-water phase boundary within the resolution of 25 um/pixel. Only by this step, an accurate direct determination of an important parameter for gas-exchange studies, the boundary-layer thickness, is feasible. The developed methods were applied to systematic gas-transfer measurements mostly with surfactants, conducted in a range of wind speeds between 0.8-7 m/s in a circular wind-wave facility. The measured gas-transfer velocities compared extremely well to exchange rates derived from mass-balance methods. The novel visualisation technique drastically increased the poor signal quality inherent to standard LIF techniques. This enabled accurate measurements of gas-transfer velocities from aqueous concentration profiles for the first time.},
	url = {http://www.ub.uni-heidelberg.de/archiv/7672},
	author = {A. Falkenroth}
}
@conference {falkenroth2006a,
	title = {Imaging concentration profiles of water boundary layer by Double-Dye LIF and inverse modelling},
	booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Spring Conference, Heidelberg, 15.-17.03.2006},
	year = {2006},
	publisher = {Deutsche Physikalische Gesellschaft},
	organization = {Deutsche Physikalische Gesellschaft},
	url = {http://www.dpg-verhandlungen.de/2006/heidelberg/up.html},
	author = {A. Falkenroth and Bernd J{\"a}hne}
}
@conference {falkenroth2006,
	title = {Visualization of air-water gas exchange using novel fluorescent dyes},
	booktitle = {12th Intern. Symp. on Flow Visualization, G{\"o}ttingen, 10--14. September 2006},
	year = {2006},
	doi = {10.5281/zenodo.14844},
	author = {A. Falkenroth and Alexandra G. Herzog and Bernd J{\"a}hne}
}
