Optimization of data retrieval process for spectroscopic CO2 isotopologue ratio measurements

• Published in: Laser physics Vol. 27; no. 5
• Main Authors: Hovorka, J, ermák, P, Veis, P
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.05.2017
• Subjects: cavity ring down; isotopologues; laser spectroscopy
• ISSN: 1054-660X; 1555-6611
• DOI: 10.1088/1555-6611/aa64b8

In this work, a numerical model was developed for critical evaluation of the 13CO2/12CO2 ratio retrievals (Δδ value) from laser absorption spectra. The goal of the analysis was to determine the dependency of the absolute error of δ on different experimental parameters, in order to find the optimal conditions for isotopic ratio retrievals without using calibrated reference samples. In our study, the target precision for Δδ was set at a level of 1%. The analysis was performed in the spectral range of the ν1+ν3 CO2 band at 1.6 μm, with the theoretical data originating from the HITRAN database. The proposed fitting algorithm allowed efficient compensation of the interference from weak transitions which are not well recognizable in a single spectrum. This effect was found to make a dominant contribution to the Δδ value. Next, the optimal conditions for such an experiment regarding the pressure, spectral range and spectrum noise were found and discussed from the perspective of widely tunable laser applications.