Imaging of bromine oxide and formaldehyde using Fabry-Perot interferometer correlation spectroscopy

Imaging of atmospheric trace gases in the UV and visible wavelength range provides insights into the spatial distribution of physical and chemical processes in the atmosphere. This is of particular advantage when observing fast-emitting point sources such as volcanoes. For this purpose, instruments are required that do not only combine a high spatio-temporal resolution with a high trace gas selectivity, but that are also robust and compact enough to be used in field measurements. In this thesis, a prototype imaging instrument for formaldehyde (HCHO) and bromine oxide (BrO) based on Fabry-Perot interferometer correlation spectroscopy in the UV wavelength range is presented. The technique makes use of the periodic transmission spectrum of a Fabry-Perot-Interferometer and its correlation with the approximately periodic narrowband absorption structures of the target trace gas. This approach combines a high spatio-temporal resolution and a high spectral selectivity. The feasibility of the technique is examined in a model study yielding instrument sensitivities of kHCHO = 1.82 x 10^-20 cm²/molec and kBrO = 5.29 x 10^-18 cm²/molec for HCHO and BrO, respectively. Furthermore, instrument characterization and testing in the laboratory shows good agreement between model and measurement. Finally, first field studies with the prototype instrument reveals a detection limit for BrO of 1 x 10^14 molec/cm² for a spatial resolution of 50 x 50 pixels and a temporal resolution of 10s. This should be suficient to investigate BrO gradients in volcanic plumes with high halogen content and contribute to understanding the volcanic plume chemistry.

Level thesis:degree_level

master

Grantor dc:publisher

Universität Heidelberg

Year

2021

Author dc:creator

• Alexander, Nies

Contributors dc:contributor

• Platt, Ulrich

Repository record source_url

http://www.ub.uni-heidelberg.de/archiv/31464

OAI identifier oai:identifier

oai:archiv.ub.uni-heidelberg.de:31464