High performance optical spectroscopy for the study of isotopic CO2 anomalies in natural carbonates

The study of the isotopic composition of natural materials ('isotopic tracers') is one of the main sources of information for the study of environments and major physico-chemical cycles in nature (e. g. carbon or water cycles). In geosciences, most isotope measurements are made by mass spectrometry and require extreme levels of sensitivity and accuracy. In collaboration with geochemists from the Laboratoire des Sciences du Climat et de l'environnement (LSCE, UMR 8212), LIPhy has been developing for several years measurement instruments based on infrared spectroscopy ('VCOF-CRDS'), dedicated to the analysis of isotopes and isotopologues in various molecules (CO2, H2O, H2S, etc.). The objective of this thesis is, in a first step, to optimize the last generation of these prototypes to achieve ultra-precise measurements on small CO2 samples, corresponding to considerable gains in terms of measurement speed and simplicity for several important isotopic tracers (Δ17O, Δ16O13C18O), allowing access - for the first time - to new isotopic tracers (Δ18O12C18O) previously inaccessible. In a second step, the doctoral student will apply this technique, in close collaboration with LSCE geochemists, to validate new approaches to reconstruct past climates (paleo-temperatures recorded in speleothems) and to better understand certain bio-calcification mechanisms on which the natural regulation of atmospheric carbon is partly based. In the longer term, the results of this thesis will contribute to the development of a new generation of ultra-precise laser spectrometers, suitable for the study of many other molecules (H2O, CH4, N2O, H2S...), with a very wide range of scientific applications in molecular spectroscopy and geoscience.

The jury is composed of:
Lucile Rutkowski, Caroline Champenois, Joele Vialon, Christof Janssen, Robert Georges et Laurent Truche