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Sub-permille accuracy spectral line intensity of the various atmospheric molecules (such as CO, N2O, CO2) is important for terrestrial remote sensing. It also provides an alternative route toward an accurate determination of amount fraction of substances in the gas phase. The Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology (CCQM) has initiated the Task Group on Advanced Spectroscopy (TGAS) to embrace this new opportunity. In contract to conventional gravimetric gas standards, optical method based on accurate line intensity is particularly advantageous for reactive species. Moreover, broadband spectroscopic method supported with sub-permille accuracy line intensities of CO have the potential to become a new primary standard of temperature [1]. Finally, absolute optical measurements of isotopic composition of CO2 based on accurate line intensities having uncertainties at the permille level have recently been demonstrated at NIST. This method is shown to be competitive with traditional artifacts-based isotopic standards. Despite the importance of such high accuracy measurement of molecular spectral line intensities, there is hardly any traceable measurement at this level of accuracy until our recent study of CO line intensities motivated by the CCQM-TGAS [2]. In this presentation, we give an overview of our metrologically-characterized FTIR facility for measuring high accuracy traceable spectral reference data at PTB which is originated from the EUMETRISPEC project. Example results on the accurate CO line intensity at permille level [3] and a coherent dataset of N2O line intensity at sub-percentage level, and absorption cross-section data of halogenated VOCs are given. For a broader scope, we also present the group ongoing and planned activities on accurate spectral reference data of NH3, H2O, and NO2 based on both above FTIR infrastructure and metrologically characterized TDLAS-based measurement systems, in action to support climate observations and energy transitions. [1] Selected Research Topics SRT-s14 Primary spectrometric thermometry for gases, http://www.metpart.eu/iem-call-2022 [2] Bielska et al. Subpromille measurements and calculations of CO (3–0) overtone line intensities, PRL Editor’s Suggestion (In press) [3] V. Werwein, G.Li, A. Serdyukov, J. Brunzendorf, O. Werhahn, V. Ebert, J. Mol. Spectrosc., 2018, 348, 68.
Topic : Theme 1: Atmospheric Chemistry and Physics.
Reference : T1-A38
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