Influence of gas humidity on the reflection coefficient of multilayer dielectric mirrors

Serdyukov, V. I.; Sinit︠s︡a, L. N.; Lugovskoi, A. A.

doi:10.1364/ao.55.004763

Cited by 7 publications

(2 citation statements)

References 11 publications

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“…Recently, Serdyukov et al . [] measured an increasing reflectivity of their mirrors (in the blue range) with water vapor pressure. Such an effect may lead to significant underestimation of the measured CRDS continuum absorption.…”

Section: Introductionmentioning

confidence: 99%

Accurate laboratory determination of the near‐infrared water vapor self‐continuum: A test of the MT_CKD model

et al. 2016

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The semi‐empirical MT_CKD model of the absorption continuum of water vapor is widely used in atmospheric radiative transfer codes of the atmosphere of Earth and, recently, of exoplanets but lacks of experimental validation in the atmospheric windows. Recent laboratory measurements by Fourier transform Spectroscopy led to self‐continuum cross sections much larger than the MT_CKD values in the near‐infrared transparency windows. We report on accurate measurements by Cavity Ring Down Spectroscopy (CRDS) and Optical Feedback‐Cavity‐Enhanced Absorption Spectroscopy (OF‐CEAS) at selected spectral points of the transparency windows centered around 4.0, 2.1, and 1.25 µm. The temperature dependence of the absorption continuum at 4.38 µm is measured in the 23–39°C range. The self‐continuum water vapor absorption is derived either from the baseline variation of water vapor spectra recorded for a series of pressure values over a small spectral interval or from baseline monitoring at fixed laser frequency during pressure ramps. After subtraction of the local water monomer lines contribution, self‐continuum cross sections, Cs, are determined with an accuracy better than 10% from the pressure squared dependence of the continuum absorption measured up to about 15 Torr. Together with our previous measurements in the 2.1 and 1.6 µm windows, the present results provide a unique set of water vapor cross sections for testing the MT_CKD model in four transparency windows. Although showing some important deviations of the absolute values (up to about a factor 4), our accurate measurements validate the overall frequency dependence of the most recent version (V2.8) of the MT_CKD model.

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Section: Introductionmentioning

confidence: 99%

Accurate laboratory determination of the near‐infrared water vapor self‐continuum: A test of the MT_CKD model

et al. 2016

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“…However, it is also possible that a similar issue could have affected the CRDS measurements (e.g. [32]), and that the observed deviation from the exp(−D 0 /T ) temperature dependence in CAVIAR is physical. More work (both experimental and theoretical) is therefore required to understand the water vapor self-continuum and its temperature dependence.…”

Section: Discussionmentioning

confidence: 99%

Cross-sections for heavy atmospheres: H$_2$O continuum

Anisman,

Chubb,

Elsey

et al. 2021

Preprint

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Most of the exoplanets detected up to now transit in front of their host stars, allowing for the generation of transmission spectra; the study of exoplanet atmospheres relies heavily upon accurate analysis of these spectra. Recent discoveries mean that the study of atmospheric signals from low-mass, temperate worlds are becoming increasingly common. The observed transit depth in these planets is small and more difficult to analyze. Analysis of simulated transmission spectra for two small, temperate planets (GJ 1214 b and K2-18 b) is presented, giving evidence for significant differences in simulated transit depth when the water vapor continuum is accounted for when compared to models omitting it. These models use cross-sections from the CAVIAR lab experiment for the water self-continuum up to 10,000 cm −1 ; these cross-sections exhibit an inverse relationship with temperature, hence lower-temperature atmospheres are the most significantly impacted. Including the water continuum strongly affects transit depths, increasing values by up to 80 ppm, with the differences for both planets being detectable with the future space missions Ariel and JWST. It is imperative that models of exoplanet spectra move toward adaptive cross-sections, increasingly optimized for H 2 O-rich atmospheres. This necessitates including absorption contribution from the water vapor continuum into atmospheric simulations.

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