Direct measurement of the Rayleigh scattering cross section in various gases

Sneep, Maarten; Ubachs, Wim

doi:10.1016/j.jqsrt.2004.07.025

Cited by 317 publications

(259 citation statements)

References 33 publications

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“…The detection system was calibrated by filling the chamber with 4 mbars of Ar gas. The known Rayleigh scatter cross section for this gas 27 then be used to compare the scatter signal and the measured energy of the laser pulse. In this way, we were able to infer the electron density, at the lower densities, from the overall Thomson scatter and the temperature from the shape of the scatter spectrum, assuming a Maxwellian electron distribution.…”

Section: Methodsmentioning

confidence: 99%

Optical Thomson scatter from a laser-ablated magnesium plume

Delserieys

Khattak

Lewis

et al. 2009

Journal of Applied Physics

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We have carried out an optical Thomson scatter study of a KrF laser-ablated Mg plume. The evolution of the electron temperature and density at distances 2 -5 mm from the target surface has been studied. We have observed that the electron density falls more rapidly than the atomic density and believe that this is a result of rapid dielectronic recombination. A comparison of the electron density profile and evolution with simple hydrodynamic modeling indicates that there is a strong absorption of the laser in the plasma vapor above the target, probably due to photoionization. We also conclude that an isothermal model of expansion better fits the data than an isentropic expansion model. Finally, we compared data obtained from Thomson scatter with those obtained by emission spectroscopy under similar conditions. The two sets of data have differences but are broadly consistent.

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Section: Methodsmentioning

confidence: 99%

Optical Thomson scatter from a laser-ablated magnesium plume

Delserieys

Khattak

Lewis

et al. 2009

Journal of Applied Physics

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“…In the case of Venus, the diffusion is mainly caused by CO 2 : the scattering cross section is 8/3x 4 (n 2 − 1) 2 /(n 2 + 1) 2 (see, e.g., Lecavelier des Etangs et al 2008a), where n is the refractive index of the gas. For CO 2 , we use the formula of Sneep & Ubachs (2005) to calculate n as a function of wavelength. The upper haze is composed by particles with sizes larger than the wavelength (4 < ∼ x < ∼ 300).…”

Section: Atmospherementioning

confidence: 99%

Transmission spectrum of Venus as a transiting exoplanet

Ehrenreich

Vidal‐Madjar

Widemann

et al. 2011

A&A

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On 5-6 June 2012, Venus will be transiting the Sun for the last time before 2117. This event is an unique opportunity to assess the feasibility of the atmospheric characterisation of Earth-size exoplanets near the habitable zone with the transmission spectroscopy technique and provide an invaluable proxy for the atmosphere of such a planet. In this letter, we provide a theoretical transmission spectrum of the atmosphere of Venus that could be tested with spectroscopic observations during the 2012 transit. This is done using radiative transfer across Venus' atmosphere, with inputs from in-situ missions such as Venus Express and theoretical models. The transmission spectrum covers a range of 0.1-5 μm and probes the limb between 70 and 150 km in altitude. It is dominated in UV by carbon dioxide absorption producing a broad transit signal of ∼20 ppm as seen from Earth, and from 0.2 to 2.7 μm by Mie extinction (∼5 ppm at 0.8 μm) caused by droplets of sulfuric acid composing an upper haze layer above the main deck of clouds. These features are not expected for a terrestrial exoplanet and could help discriminating an Earth-like habitable world from a cytherean planet.

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“…Molecular nitrogen contributes to the transmission spectrum via the Rayleigh-scattering of light. The Rayleigh-scattering cross section of N 2 depends on the N 2 refractive index, which is calculated according to Sneep & Ubachs (2005). Within the SOPHIE spectral range, molecular oxygen contributes to the transmission spectrum through i) photoabsorptions by the forbidden 1 Σ + g -3 Σ − g transition bands B (1-0) at 6880 Å and γ (2-0) at 6280 Å, and ii) through Rayleigh scattering.…”

Section: Model Calculationmentioning

confidence: 99%

“…The line parameters for the O 2 bands are extracted from the HITRAN 2008 molecular spectroscopic database (Rothman et al 2009), scaled to the atmospheric temperature and pressure profiles used, and convolved with a Gaussian profile with full-width at half-maximum matching the spectrograph resolution. The Rayleigh-scattering cross sections of O 2 are calculated following Sneep & Ubachs (2005) using refractive indices from Bates (1984). We retrieved the UV/visible photoabsorption cross section of O 3 at 293 K and 1 bar from the GEISA 1997 data base (Jacquinet-Husson et al 1999).…”

Section: Model Calculationmentioning

confidence: 99%

The Earth as an extrasolar transiting planet

Vidal‐Madjar

Arnold

Ehrenreich

et al. 2010

A&A

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Context. An important goal within the quest for detecting an Earth-like extrasolar planet, will be to identify atmospheric gaseous bio-signatures. Aims. Observations of the light transmitted through the Earth's atmosphere, as for an extrasolar planet, will be the first important step for future comparisons. We have completed observations of the Earth during a lunar eclipse, a unique situation similar to that of a transiting planet. We aim at showing what species could be detected in its atmosphere at optical wavelengths, where a lot of photons are available in the masked stellar light. Methods. We present observations of the 2008 August 16 Moon eclipse performed with the SOPHIE spectrograph at the Observatoire de Haute-Provence (France). Locating the spectrograph's fibers in the penumbra of the eclipse, the Moon irradiance is then a mix of direct, unabsorbed Sun light and solar light that has passed through the Earth's atmosphere. This mixture essentially reproduces what is recorded during the transit of an extrasolar planet. Results. We report here the clear detection of several Earth atmospheric compounds in the transmission spectra, such as ozone, molecular oxygen, and neutral sodium as well as molecular nitrogen and oxygen through the Rayleigh signature. Moreover, we present a method that allows us to derive the thickness of the atmosphere versus the wavelength for penumbra eclipse observations. We quantitatively evaluate the altitude at which the atmosphere becomes transparent for important species like molecular oxygen and ozone, two species thought to be tightly linked to the presence of life. Conclusions. The molecular detections presented here are an encouraging first attempt, necessary to better prepare for the future of extremely-large telescopes and transiting Earth-like planets. Instruments like SOPHIE will be mandatory when characterizing the atmospheres of transiting Earth-like planets from the ground and searching for bio-marker signatures.

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Direct measurement of the Rayleigh scattering cross section in various gases

Cited by 317 publications

References 33 publications

Optical Thomson scatter from a laser-ablated magnesium plume

Optical Thomson scatter from a laser-ablated magnesium plume

Transmission spectrum of Venus as a transiting exoplanet

The Earth as an extrasolar transiting planet

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