Frankfurt 2006 – scientific programme

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Q: Quantenoptik und Photonik

Q 66: Laser in der Medizin und Umweltmeßtechnik

Q 66.4: Talk

Thursday, March 16, 2006, 15:45–16:00, HII

Rapidly Swept CW Cavity Ring-down Laser Spectroscopy for Carbon Isotope Analysis — •Hideki TOMITA^1,2, Yu TAKIGUCHI¹, Kenichi WATANABE¹, Jun KAWARABAYASHI¹, and Tetsuo IGUCHI¹ — ¹Dept. of Quantum Eng., Nagoya Univ., Nagoya, 464-8603, Japan — ²Institute of Physics, Johannes Gutenberg Univ., Mainz, D-55128, Germany

Ultra trace detection of stable or long lived carbon isotope tracers is widely used in many fields of research. Particularly, in-field measurements of carbon isotope ratios are required for environmental studies, e.g. on the ground-level carbon cycle in forests and volcanic gas emission. With the aim of developing a portable system for in-field isotope analysis, we investigate isotope analysis based on Rapidly Swept CW Cavity Ring-Down Laser Spectroscopy [1]. Basic performance of this system for ¹³C/¹²C isotope analysis was measured in overtone absorption lines of ¹²C¹⁶O₂ and ¹³C¹⁶O₂ using a near-IR (1.6 µm) DFB diode laser. The obtained isotopic ratio showed good agreement with the natural abundance within experimental uncertainty. The detectable concentration for ¹³C¹⁶O₂ was determined from the standard deviation of the measured ring-down rate to be 900 ppmv. Considering possible technical improvements, we estimate that a minimum detectable concentration of 0.3 ppmv would be achievable by using a diode laser at 2 µm. Thus, this system has a large potential for in-field ¹³C/¹²C and potentially also ¹⁴C/¹²C isotope analysis.

[1] Y. He and B.J. Orr, Chem. Phys. Lett. 319, 131 (2000).