Effect of pressure broadening on molecular absorption cross sections in exoplanetary atmospheres

This chapter provides a broad overview of the spectroscopic principles required in order to perform quantitative spectroscopy of atmospheres. It couples the details of atmospheric spectroscopy with the radiative transfer processes and also with the assessment of rotational, vibrational, and electronic spectroscopic measurements of atmospheres. The principles apply from line-resolved measurements (chiefly microwave through infrared) through ultraviolet and visible measurements employing absorption cross sections developed from individual transitions. The chapter introduces Einstein coefficients before in turn discussing rotational spectroscopy, vibrational spectroscopy, nuclear spin, and electronic spectroscopy.

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Black carbon and dust in the Third Pole glaciers: revaluated concentrations, mass absorption cross-sections and contributions to glacier ablation

The Science of The Total Environment ◽

10.1016/j.scitotenv.2021.147746 ◽

2021 ◽

pp. 147746

Author(s):

Yang Li ◽

Shichang Kang ◽

Xuelei Zhang ◽

Jizu Chen ◽

Julia Schmale ◽

...

Keyword(s):

Black Carbon ◽

Cross Sections ◽

Absorption Cross ◽

The Third ◽

Mass Absorption ◽

Glacier Ablation

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Ultraviolet Absorption Cross-Sections of Ammonia at Elevated Temperatures for Nonintrusive Quantitative Detection in Combustion Environments

Applied Spectroscopy ◽

10.1177/0003702821990445 ◽

2021 ◽

pp. 000370282199044

Author(s):

Wubin Weng ◽

Shen Li ◽

Marcus Aldén ◽

Zhongshan Li

Keyword(s):

Cross Section ◽

Cross Sections ◽

Absorption Cross Section ◽

Elevated Temperatures ◽

Uv Absorption ◽

Energy Utilization ◽

Quantitative Detection ◽

Absorption Cross ◽

Hot Gas

Ammonia (NH3) is regarded as an important nitrogen oxides (NOx) precursor and also as an effective reductant for NOx removal in energy utilization through combustion, and it has recently become an attractive non-carbon alternative fuel. To have a better understanding of thermochemical properties of NH3, accurate in situ detection of NH3 in high temperature environments is desirable. Ultraviolet (UV) absorption spectroscopy is a feasible technique. To achieve quantitative measurements, spectrally resolved UV absorption cross-sections of NH3 in hot gas environments at different temperatures from 295 K to 590 K were experimentally measured for the first time. Based on the experimental results, vibrational constants of NH3 were determined and used for the calculation of the absorption cross-section of NH3 at high temperatures above 590 K using the PGOPHER software. The investigated UV spectra covered the range of wavelengths from 190 nm to 230 nm, where spectral structures of the [Formula: see text] transition of NH3 in the umbrella bending mode, v2, were recognized. The absorption cross-section was found to decrease at higher temperatures. For example, the absorption cross-section peak of the (6, 0) vibrational band of NH3 decreases from ∼2 × 10−17 to ∼0.5 × 10−17 cm2/molecule with the increase of temperature from 295 K to 1570 K. Using the obtained absorption cross-section, in situ nonintrusive quantification of NH3 in different hot gas environments was achieved with a detection limit varying from below 10 parts per million (ppm) to around 200 ppm as temperature increased from 295 K to 1570 K. The quantitative measurement was applied to an experimental investigation of NH3 combustion process. The concentrations of NH3 and nitric oxide (NO) in the post flame zone of NH3–methane (CH4)–air premixed flames at different equivalence ratios were measured.

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