High-precision determination of the (CO2)-C-13/(CO2)-C-12 isotope ratio using a portable 2.008-mu m diode-laser spectrometer

Year: 2003

Authors: Gagliardi G., Castrillo A., Iannone R. Q., Kerstel E. R. Th., Gianfrani L.

Autors Affiliation: Dipartimento di Scienze Ambientali, Seconda Università di Napoli, INFM – Gruppo Coordinato Napoli 2, Via Vivaldi 43, 81100 Caserta, Italy; Center for Isotope Research, Department of Physics, University of Groningen, Groningen, Netherlands

Abstract: A compact and portable diode-laser spectrometer is developed for high-precision measurements of the (CO2)-C-13 /(CO2)-C-12 isotope ratio. Ro-vibrational transitions belonging to different combination bands, around 2.008 mum, are detected for the two isotopomers, using wavelength-modulation spectroscopy with first-harmonic detection. The determination of the isotope ratio is performed through a comparison between the spectra, simultaneously acquired in two different multiple-reflection cells designed to contain the sample and reference gases. The reproducibility of our method is extensively investigated over different time scales. In particular, the short-term precision of the isotope ratio determination is found to be 0.03%. We discuss the presence of possible systematic shifts in the delta-value and optimise the operating conditions to ensure accuracy within the precision level. A possible use for in-situ measurements in volcanic gases is also discussed.


Volume: 77 (1)      Pages from: 119  to: 124

KeyWords: Band structure; Carbon dioxide; Gases; Light modulation; Semiconductor lasers; Spectroscopic analysis, Diode laser spectrometer; Isotope ratio; Multiple reflection cells; Ro vibrational transitions; Volcanic gases, Radioisotopes
DOI: 10.1007/s00340-003-1240-5

Citations: 48
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