Measurement of the depolarization ratio of Rayleigh scattering at absorption bands

1981 ◽  
Vol 74 (2) ◽  
pp. 786-791 ◽  
Author(s):  
J. Anglister ◽  
I. Z. Steinberg
Keyword(s):  
Rayleigh Scattering ◽  
Depolarization Ratio ◽  
Absorption Bands

Depolarization ratio measurement of Rayleigh scattering in high field electric strength

1975 ◽  
Vol 55 (3) ◽  
pp. 199-200 ◽  
Author(s):  
F. Aussenegg ◽  
M. Lippitsch ◽  
R. Möller ◽  
J. Wagner
Keyword(s):  
High Field ◽  
Rayleigh Scattering ◽  
Electric Strength ◽  
Depolarization Ratio ◽  
Ratio Measurement

Polarized resonance Raman dispersion spectroscopy on metalporphyrins

2001 ◽  
Vol 05 (03) ◽  
pp. 198-224 ◽  
Author(s):  
REINHARD SCHWEITZER-STENNER
Keyword(s):  
Resonance Raman Spectroscopy ◽  
Resonance Raman ◽  
Resonance Excitation ◽  
Depolarization Ratio ◽  
Prosthetic Group ◽  
Excitation Energies ◽  
Absorption Bands ◽  
Porphyrin Macrocycle ◽  
Ideal Tool ◽  
The Relationship

Resonance Raman spectroscopy is an ideal tool to investigate the structural properties of chromophores embedded in complex (biological) environments. This holds particularly for metalporphyrins which serve as prosthetic group in various proteins. Resonance Raman dispersion spectroscopy involves the measurement of resonance excitation and depolarization ratios of a large number of Raman lines at various excitation energies covering the spectral region of the chromophore's optical absorption bands. Thus, one obtains resonance excitation profiles and the depolarization ratio dispersion of these bands. While the former contains information about the structure of excited electronic states involved in the Raman scattering process, the latter reflects asymmetric perturbations which lower the porphyrin macrocycle symmetry from ideal D4h. The article introduces and compares different quantum mechanical approaches designed to quantitatively analyze both resonance excitation and the relationship between symmetry lowering and depolarization ratio dispersion.

Validation for ESA’s Aeolus Mission using the in-situ instruments at Canadian Arctic and reanalysis data

2020 ◽  
Author(s):  
Chih-Chun Chou ◽  
Paul Kushner ◽  
Zen Mariani ◽  
Peter Rodriguez ◽  
Christopher Fletcher
Keyword(s):  
Climate Change ◽  
Rayleigh Scattering ◽  
Line Of Sight ◽  
Horizontal Line ◽  
Vertical Resolution ◽  
Doppler Lidar ◽  
Depolarization Ratio ◽  
Ka Band ◽  
Wind Profiles

<p>ESA’s Aeolus mission, launched in August 2018, is designed to capture tropospheric wind profiles on a global scale in near-real time. The Aeolus lidar system, Atmospheric LAser Doppler INstrument (ALADIN), uses two modes of lidar-driven active scattering, Mie and Rayleigh scattering channels, to retrieve horizontal line-of-sight (HLOS) winds under both clear and cloudy conditions. ESA Aeolus aims to improve numerical weather and climate prediction, and to advance understanding of atmospheric circulation and weather systems.</p><p>This presentation will describe the Canadian validation activities for ESA Aeolus level-2B product, coordinated by the University of Toronto’s Department of Physics and Environment and Climate Change Canada (ECCC). The main focus is the evaluation of Aeolus overpasses using the fifth major global reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ECMWF ERA5), and in-situ measurements at Environment and Climate Change Canada’s (ECCC) Iqaluit and Whitehorse supersites where several wind sensing instruments are co-located. It will compare the Aeolus HLOS winds with the profiles of wind vector from regular radiosonde launches, line-of-sight winds from Doppler Lidar and Ka-Band Radar. The accuracy of the Aeolus measurements is analyzed based on the type of scattering and natural variability of the wind on different levels.</p><p>The radiosonde measures the profiles of temperature, relative humidity, pressure, and winds twice a day with a vertical resolution of 15 m up to 30 km. On the other hand, the Mie scattered 1.5 micron Doppler Lidar retrieves LOS winds at every 3 m as well as aerosol backscatter and depolarization ratio every 5 minutes up to 3 km. Lastly, for every 10 minutes, the dual-polarization Doppler Ka-Band Radar measures the LOS wind speed and direction, cloud and fog backscatter, and depolarization ratio up to a range of 25 km with a vertical resolution of 10 m.</p><p>The wind profiles were directly compared to the profiles derived from other instruments or reanalysis. The vertical structure of the Aeolus winds, for example the wind shear, will also be compared and discussed. The validation results showed that Aeolus is providing some promising initial products and that the ERA5 reanalysis is the most consistent dataset with the Aeolus wind measurements from level-2B product.</p>

scholarly journals Discriminating between hazy and clear hot-Jupiter atmospheres with CARMENES

2020 ◽  
Vol 643 ◽  
pp. A24
Author(s):  
A. Sánchez-López ◽  
M. López-Puertas ◽  
I. A. G. Snellen ◽  
E. Nagel ◽  
F. F. Bauer ◽  
...  
Keyword(s):  
High Altitude ◽  
Water Vapour ◽  
Rayleigh Scattering ◽  
Near Infrared ◽  
Relative Strength ◽  
High Spectral Resolution ◽  
Absorption Bands ◽  
Infrared Wavelength ◽  
Hot Jupiters ◽  
Water Vapour Absorption

Context. Relatively large radii of some hot Jupiters observed in the ultraviolet and blue-optical are generally interpreted to be due to Rayleigh scattering by high-altitude haze particles. However, the haze composition and its production mechanisms are not fully understood, and observational information is still limited. Aims. We aim to study the presence of hazes in the atmospheres of HD 209458 b and HD 189733 b with high spectral resolution spectra by analysing the strength of water vapour cross-correlation signals across the red optical and near-infrared wavelength ranges. Methods. A total of seven transits of the two planets were observed with the CARMENES spectrograph at the 3.5 m Calar Alto telescope. Their Doppler-shifted signals were disentangled from the telluric and stellar contributions using the detrending algorithm SYSREM. The residual spectra were subsequently cross-correlated with water vapour templates at 0.70–0.96 μm to measure the strength of the water vapour absorption bands. Results. The optical water vapour bands were detected at 5.2σ in HD 209458 b in one transit, whereas no evidence of them was found in four transits of HD 189733 b. Therefore, the relative strength of the optical water bands compared to those in the near-infrared were found to be larger in HD 209458 b than in HD 189733 b. Conclusions. We interpret the non-detection of optical water bands in the transmission spectra of HD 189733 b, compared to the detection in HD 209458 b, to be due to the presence of high-altitude hazes in the former planet, which are largely absent in the latter. This is consistent with previous measurements with the Hubble Space Telescope. We show that currently available CARMENES observations of hot Jupiters can be used to investigate the presence of haze extinction in their atmospheres.

Polarimetric Observations of Red Variables: A Study of Gas and Particle Interactions

1979 ◽  
Vol 46 ◽  
pp. 386-408 ◽  
Author(s):  
G. V. Coyne ◽  
I. S. McLean
Keyword(s):  
Wavelength Dependence ◽  
Stellar Atmosphere ◽  
Molecular Absorption ◽  
Absorption Bands ◽  
Absorption And Emission ◽  
Mira Variables ◽  
Stellar Photosphere ◽  
Regular Variable ◽  
Red Supergiants ◽  
Balmer Lines

AbstractIn recent years the wavelength, dependence of the polarization in a number of Mira variables, semi-regular variables and red supergiants has been measured with resolutions between 0.3 and 300 A over the range 3300 to 11000 A. Variations are seen across molecular absorption bands, especially TiO bands, and across atomic absorption and emission lines, especially the Balmer lines. In most cases one can ignore or it is possible to eliminate the effects due to interstellar polarization, so that one can study the polarization mechanisms operating in the stellar atmosphere and environment. The stars Omicron Ceti. (Mira), V CVn (semi-regular variable) and Mu Cephei (M2 la), in addition to other stars similar to them, will be discussed in some detail.Models to explain the observed polarization consider that the continuum flux is polarized either by electron, molecular and/or grain scattering or by temperature variations and/or geometrical asymmetries over the stellar photosphere. This polarized radiation is affected by atomic and molecular absorption and emission processes at various geometric depths in the stellar atmosphere and envelope. High resolution spectropolarimetry promises, therefore, to be a power-rul tool for studying stratification effects in these stars.

Investigation of the fine structure in overtone absorption bands of 12C2H4

1999 ◽  
Vol 97 (1) ◽  
pp. 265-277 ◽  
Author(s):  
M. BACH, R. GEORGES, M. HERMAN, A. PER
Keyword(s):  
Fine Structure ◽  
Absorption Bands
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