L’Institut Foton vous convie à la présentation des travaux de thèse de doctorat :
Submillimeter spectroscopy instrument for detection of volatile soil emissions
Daria GUDZ
sous la direction de François Bondu et Françoise Binet.
Cette soutenance publique aura lieu le mercredi 29 octobre 2025 à 9h30 à l’amphithéâtre du PNRB (Campus de Beaulieu, à Rennes)
Assister à la soutenance par Zoom :
https://univ-rennes1-fr.zoom.us/j/62611687200
ID de réunion: 626 1168 7200
Code secret: 768375
The thesis focuses on soil volatile organic compound (VOC) emissions, which are increasingly recognized as sensitive indicators of human impact and climate change. While current detection methods remain limited by low compound identification rates, this work proposes a novel approach: enhancing metabolite databases with structural information derived from rotational spectroscopy. To support this, a dedicated submillimeter spectrometer was designed and assembled. The system is based on a DC–800 GHz optical frequency synthesizer, which was improved and characterized, achieving a frequency precision of 2·10-6 and a synthesized linewidth of 40 kHz, enabling spectroscopy experiments at low pressures (below 1 mbar). The frequency synthesizer was calibrated below 42 GHz, allowing extrapolation to higher frequencies. A submillimeter spectroscopy bench was also designed and assembled, including a cavity adapted for low-pressure (mbar) measurements. Homodyne detection was optimized, eliminating baseline modulation. The first spectroscopic measurements in our laboratory in this frequency range were performed on acetonitrile. We modeled how instrument noise impacts the signal-to-noise ratio of measurements and determined the detection threshold for this molecule. Future applications include identifying complex VOCs such as methyl salicylate and linking microbial metabolic activity to environmental signals.
The work was conducted within an interdisciplinary collaboration between the Ecobio and the Foton Institute research units, bridging physics and ecology to provide new insights into soil health and environmental monitoring.