{"title":"Measurement of high-temperature absorption cross-sections using an optical cell with a non-uniform temperature distribution","authors":"Ihsan Farouki, Aamir Farooq, Bassam Dally","doi":"10.1016/j.jqsrt.2024.109243","DOIUrl":null,"url":null,"abstract":"<div><div>A mathematical method to enable absorption cross-section measurements using an optical cell with a non-uniform temperature distribution is formulated, validated and experimentally demonstrated in this study. The motivation of the proposed method is to facilitate high-temperature spectroscopic studies in the long-wavelength mid-IR region, and to offer an alternative to highly engineered optical cells. The method is based on virtual segmentation of the non-uniform temperature field within an optical cell into bins, each having a sufficiently uniform temperature. By collecting a set of absorbance measurements corresponding to unique temperature profiles and expressing the temperature dependence of the absorption cross-section in terms of a model with limited number of unknowns, a closed-form system of equations is obtained which can be solved to evaluate absorption cross-sections. It is shown, through a set of simulated validation cases, that modeling the temperature dependence in terms of a third order polynomial results in accurate reconstruction of the cross-section spectra for a wide range of cases. Piece-wise polynomials and an alternative nonlinear model are proposed for improved accuracy and to model potentially complex temperature dependencies of the absorption cross-sections. To demonstrate the application of the proposed method, an optical cell with a non-uniform temperature profile was used to measure the cross-section spectra of methane over 1280 – 1330 cm<sup>-1</sup> at temperatures up to 523 K. The proposed method is expected to be highly useful in collecting spectroscopic data at high temperatures particularly in the mid-infrared region.</div></div>","PeriodicalId":16935,"journal":{"name":"Journal of Quantitative Spectroscopy & Radiative Transfer","volume":"330 ","pages":"Article 109243"},"PeriodicalIF":2.3000,"publicationDate":"2024-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Quantitative Spectroscopy & Radiative Transfer","FirstCategoryId":"101","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0022407324003509","RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"OPTICS","Score":null,"Total":0}
引用次数: 0
Abstract
A mathematical method to enable absorption cross-section measurements using an optical cell with a non-uniform temperature distribution is formulated, validated and experimentally demonstrated in this study. The motivation of the proposed method is to facilitate high-temperature spectroscopic studies in the long-wavelength mid-IR region, and to offer an alternative to highly engineered optical cells. The method is based on virtual segmentation of the non-uniform temperature field within an optical cell into bins, each having a sufficiently uniform temperature. By collecting a set of absorbance measurements corresponding to unique temperature profiles and expressing the temperature dependence of the absorption cross-section in terms of a model with limited number of unknowns, a closed-form system of equations is obtained which can be solved to evaluate absorption cross-sections. It is shown, through a set of simulated validation cases, that modeling the temperature dependence in terms of a third order polynomial results in accurate reconstruction of the cross-section spectra for a wide range of cases. Piece-wise polynomials and an alternative nonlinear model are proposed for improved accuracy and to model potentially complex temperature dependencies of the absorption cross-sections. To demonstrate the application of the proposed method, an optical cell with a non-uniform temperature profile was used to measure the cross-section spectra of methane over 1280 – 1330 cm-1 at temperatures up to 523 K. The proposed method is expected to be highly useful in collecting spectroscopic data at high temperatures particularly in the mid-infrared region.
期刊介绍:
Papers with the following subject areas are suitable for publication in the Journal of Quantitative Spectroscopy and Radiative Transfer:
- Theoretical and experimental aspects of the spectra of atoms, molecules, ions, and plasmas.
- Spectral lineshape studies including models and computational algorithms.
- Atmospheric spectroscopy.
- Theoretical and experimental aspects of light scattering.
- Application of light scattering in particle characterization and remote sensing.
- Application of light scattering in biological sciences and medicine.
- Radiative transfer in absorbing, emitting, and scattering media.
- Radiative transfer in stochastic media.