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UP: Fachverband Umweltphysik

UP 2: Atmosphere - trace gases, Methods - remote sensing

UP 2.4: Vortrag

Montag, 5. März 2018, 11:45–12:00, G 1.011

Precise, direct, simultaneous spectroscopic measurements of CO₂ singly- and doubly-substituted isotopologues — •Ivan Prokhorov^1,2, Tobias Kluge¹, and Christof Janssen^1,2 — ¹Institute of Environmental Physics, Heidelberg University, Heidelberg, Germany — ²LERMA-IPSL, Sorbonne University, UPMC Univ. Paris 06, CNRS, Observatoire de Paris, PSL Research University, Paris, France

The ¹⁷O/¹⁸O anomaly (Δ¹⁷O) and the "clumped isotope" composition Δ_{¹⁶O¹³C¹⁸O} in CO₂ are new tools for quantification of temperature dependent equilibrium and non-equilibrium processes in a variety of environmental systems, requiring the analysis of multiple carbon dioxide isotopologues. Here, we present a laser-based measurement technique for precise, direct and simultaneous measurements of the six most abundant CO₂ isotopologues, including the two rare and doubly-substituted species ¹⁶O¹³C¹⁸O and ¹⁶O¹³C¹⁷O. The prototype absorption spectrometer uses two intra-band cascade lasers (ICL) at 4.3 and 4.4 µm to detect CO₂ absorption lines in the fundamental ν₃ band. Dry pure carbon dioxide samples (≤100 µmol) are analysed in a custom built multipass Herriot cell equipped with two optical path lengths of 9 cm and 9 m. A full operation cycle consists of several comparisons of the sample gas with the working reference (6–10 minutes per one comparison). Within one hour of measurements, a reproducibility at the level of 50 ppm (1SEM) is obtained. The performance of the instrument is comparable with the state of the art mass-spectrometers, but void of isobaric interferences.