Oxygen Absorption Band Research Articles

Temperature Dependence of the 1727 cm–1 Interstitial Oxygen Absorption Band Studied by Attenuated Total Internal Reflection Infrared Spectroscopy in a Newly Developed Microreactor

In this work we study oxygen interstitial defects (Oi) in a silicon-technology-based microreactor with an integrated attenuated total internal reflection (ATR) crystal as a function of an externally applied potential by means of attenuated total internal reflection infrared spectroscopy (ATR-IR). A reduction of the 1727 cm–1 Oi IR absorption band is observed with increasing potential. We evidence that this band is related to the presence of Oi, which enables detection of Oi by ATR-IR spectroscopy. The observed reduction with increasing potential is ascribed to an increase in temperature, due to resistive heating of the silicon.

Theoretical analysis of the effect of meteorologic factors on passive ranging technology based on oxygen absorption spectrum

The passive ranging technology can be used to accurately estimate range from sensor to target. It can simultaneously carry out detecting, tracking, locating and alarming of boost phase missiles and rocket planes. The Oxygen absorption band, located in visible light and near infrared band, has unique spectral lineshape, independent absorption spectrum, large dynamic range and relatively smaller absorption characteristic, and then could carry out the high precision and stability distance measuring for auto-power aerial vehicle. In order to discuss the effect of different meteorologic factors on this technique, this paper researched the Oxygen absorption spectral characteristics and introduced the basic principle of the passive ranging in detail, and then theoretically analyzed and numerically simulated the effect of the meteorologic factors to passive ranging technology. Research result shows that the passive ranging based on the Oxygen absorption spectrum has good adaptability and stability, and the worsening of meteorologic factors only reduces the efficient measurement range of the system, and then does not have any effect for ranging accuracy in the validity range. The result will provide a certain amount of theoretical and experimental basis for the research and application of the passive ranging based on Oxygen absorption spectrum.

Atmospheric correction of MERIS data on the black pixel assumption in oxygen and water vapor absorption bands

Atmospheric correction of MERIS data on the black pixel assumption in oxygen and water vapor absorption bands

Continuous Monitoring of Canopy Level Sun-Induced Chlorophyll Fluorescence During the Growth of a Sorghum Field

A field platform dedicated to fluorescence measurements (INRA, Avignon, France) was used to monitor the fluorescence emission of a sorghum field during its growing period. The measurements were performed continuously at the canopy level, from seeding to maturity. A passive instrument based on three spectrometers was used to monitor the evolution of fluorescence fluxes and vegetation indexes such as Photochemical Reflectance Index (PRI) and Normalized Difference Vegetation Index (NDVI). Fluorescence fluxes were retrieved from radiances, using the filling-in of the atmospheric oxygen absorption bands, at 687 and 760 nm. In parallel, leaf fluorescence spectra, canopy height, and leaf chlorophyll contents were acquired during the growth. Both PRI and NDVI indexes varied with the development of the sorghum field: we observed that NDVI was more sensitive during the early stage of the growth. However, NDVI saturates before the PRI index. Fluorescence fluxes at 687 nm (Fs687) and 760 nm (Fs760) showed an overall increase: Fs687 increased more rapidly at the beginning of growth but trends to saturate while Fs760 still increase. During the growth, the Fs687/Fs760 ratio at the canopy level is found lower than at leaf level. At canopy level, the ratio decreased when the leaf chlorophyll content increases. A decrease was also observed at leaf level with a lower extend. This more important decrease of the fluorescence ratio at canopy level is attributed to a reabsorption of red fluorescence (Fs687) during its transfer through the canopy layers. In the context of forthcoming large-scale remote sensing application, the modification of the leaf level fluorescence emission by the structure of the canopy observed in this article is one of the major issues that must be addressed to interpret the fluorescence signal.

Remote Sensing of Solar-Induced Chlorophyll Fluorescence at Atmospheric Oxygen Absorption Band Around 760 nm and Simulation of That Absorption in Laboratory

The present work establishes that the usual method of remote measurement of vegetation reflectance can also detect steady-state solar-induced fluorescence of vegetation. It identifies the hyperspectral signature of chlorophyll fluorescence as a small spike on the reflectance spectral curve of vegetation at the oxygen absorption (O2-A) band around 760 nm. It justifies the origin of the fluorescence signature with both leaf- and pigment-level studies and quantifies it with the following: (1) presence/absence of chlorophyll in leaves; (2) varying concentration of chlorophyll in solution; (3) time of exposure under illumination; and (4) correctness of the calibration of leaf reflectance with respect to the standard white surface. The O2-A band is detectable in solar radiation measured on Earth because of light absorption by the atmospheric oxygen column. This paper suggests an experimental technique to simulate that absorption in laboratory also. Oxygen gas compressed at high pressure can produce the oxygen absorption band artificially at indoor condition.

CAN GROUND-BASED TELESCOPES DETECT THE OXYGEN 1.27 μm ABSORPTION FEATURE AS A BIOMARKER IN EXOPLANETS?

The oxygen absorption line imprinted in the scattered light from the Earth-like planets has been considered the most promising metabolic biomarker of the exo-life. We examine the feasibility of the detection of the 1.27 micron oxygen band from habitable exoplanets, in particular, around late- type stars observed with a future instrument on a 30 m class ground-based telescope. We analyzed the night airglow around 1.27 micron with IRCS/echelle spectrometer on Subaru and found that the strong telluric emission from atmospheric oxygen molecules declines by an order of magnitude by midnight. By compiling nearby star catalogs combined with the sky background model, we estimate the detectability of the oxygen absorption band from an Earth twin, if it exists, around nearby stars. We find that the most dominant source of photon noise for the oxygen 1.27 micron band detection comes from the night airglow if the contribution of the stellar PSF halo is suppressed enough to detect the planet. We conclude that the future detectors for which the detection contrast is limited by photon noise can detect the oxygen 1.27 micron absorption band of the Earth twins for ~50 candidates of the late type star. This paper demonstrates the importance of deploying small inner working angle efficient coronagraph and extreme adaptive optics on extremely large telescopes, and clearly shows that doing so will enable study of potentially habitable planets.

Photochemical investigation of the IR absorption bands of molecular oxygen in organic and aqueous environment

It is shown that the weak IR absorption bands corresponding to the forbidden triplet-singlet transitions in oxygen molecules can be reliably studied in air-saturated solvents under ambient conditions using measurements of the photooxygenation rates of singlet oxygen traps (1,3-diphenylisobenzofuran or uric acid) upon direct excitation of oxygen molecules by IR diode lasers. The best results were obtained from comparison of the oxygenation rates upon direct and photosensitized singlet oxygen excitation. In the present paper, this method was applied to estimation of the absorbance (A(ox)) and molar absorption coefficients (ε(ox)) corresponding to the oxygen absorption bands at 765 and 1273 nm in carbon tetrachloride, acetone, alcohols and water. In carbon tetrachloride, the band at 1073 nm was also investigated. Correlation of the obtained data with the luminescence spectra and radiative rate constants of singlet oxygen, contribution of oxygen dimols and biological significance of the studied effects are discussed.

Vicarious calibrations of HICO data acquired from the International Space Station

The Hyperspectral Imager for the Coastal Ocean (HICO) presently onboard the International Space Station (ISS) is an imaging spectrometer designed for remote sensing of coastal waters. The instrument is not equipped with any onboard spectral and radiometric calibration devices. Here we describe vicarious calibration techniques that have been used in converting the HICO raw digital numbers to calibrated radiances. The spectral calibration is based on matching atmospheric water vapor and oxygen absorption bands and extraterrestrial solar lines. The radiometric calibration is based on comparisons between HICO and the EOS/MODIS data measured over homogeneous desert areas and on spectral reflectance properties of coral reefs and water clouds. Improvements to the present vicarious calibration techniques are possible as we gain more in-depth understanding of the HICO laboratory calibration data and the ISS HICO data in the future.

An investigation of the near-infrared collision induced absorption bands of oxygen with SCIAMACHY solar occultation data

The present work investigates the Collision Induced Absorption (CIA) bands of oxygen that occur at 1065 and 1270nm from solar occultation data obtained with the space-borne spectrometer SCIAMACHY. The effort is motivated by the interest in these two strong CIA bands in atmospheric research and the paucity of data on them under realistic atmospheric conditions. The observing geometry provides long integration paths and in turn easily measurable absorption signals. Our analysis method relies on the accurate separation of the CIA band signature from the rest of the continuum and structured components over selected spectral intervals. We show that the shapes of the two CIA bands seem well described by specific laboratory determinations over a broad range of tropospheric and low-stratospheric conditions. By analyzing a full month of solar occultation data we find that the ratio of peak binary cross sections in air, σ1270nmpeak/σ1065nmpeak, is ∼4 and seemingly independent of tangent height from 6 to 18km. We tentatively estimate the absolute binary cross sections and compare them to existent measurements. A better characterization of the near-infrared CIA bands of oxygen should facilitate their implementation in remote sensing applications in the way it is often done with the CIA bands that occur in the visible.

Generation of reactive oxygen species in water under exposure to visible or infrared irradiation at absorption bands of molecular oxygen

It is found that in bidistilled water saturated with oxygen hydrogen peroxide and hydroxyl radicals are formed under the influence of visible and infrared radiation in the absorption bands of molecular oxygen. Formation of reactive oxygen species (ROS) occurs under the influence of both solar and artificial light sourses, including the coherent laser irradiation. The oxygen effect, i.e. the impact of dissolved oxygen concentration on production of hydrogen peroxide induced by light, is detected. It is shown that the visible and infrared radiation in the absorption bands of molecular oxygen leads to the formation of 8-oxoguanine in DNA in vitro. Physicochemical mechanisms of ROS formation in water when exposed to visible and infrared light are studied, and the involvement of singlet oxygen and superoxide anion radicals in this process is shown.

Atmospheric correction of ENVISAT/MERIS data over case II waters: the use of black pixel assumption in oxygen and water vapour absorption bands

The Medium Resolution Imaging Spectrometer (MERIS) sensor, with its good physical design, can provide excellent data for water colour monitoring. However, owing to the shortage of shortwave-infrared (SWIR) bands, the traditional near-infrared (NIR)–SWIR algorithm for atmospheric correction in inland turbid case II waters cannot be extended to the MERIS data directly, which limits its applications. In this study, we developed a modified NIR black pixel method for atmospheric correction of MERIS data in inland turbid case II waters. In the new method, two special NIR bands provided by MERIS data, an oxygen absorption band (O2 A-band, 761 nm) and a water vapour absorption band (vapour A-band, 900 nm), were introduced to keep the assumption of zero water-leaving reflectance valid according to the fact that both atmospheric transmittance and water-leaving reflectance are very small at these two bands. After addressing the aerosol wavelength dependence for the cases of single- and multiple-scattering conditions, we further validated the new method in two case lakes (Lake Dianchi in China and Lake Kasumigaura in Japan) by comparing the results with in situ measurements and other atmospheric correction algorithms, including Self-Contained Atmospheric Parameters Estimation for MERIS data (SCAPE-M) and the Basic ERS (European Remote Sensing Satellite) & ENVISAT (Environmental Satellite) (A)ATSR ((Advanced) Along-Track Scanning Radiometer) and MERIS (BEAM) processor. We found that the proposed method had acceptable accuracy in the bands within 560–754 nm (MERIS bands 5–10) (average absolute deviation (AAD) = 0.0081, average deviation (AD) = 0.0074), which are commonly used in the estimation models of chlorophyll-a (chl-a) concentrations. In addition, the performance of the new method was superior to that of the BEAM processor and only slightly worse than that of SCAPE-M in these bands. Considering its acceptable accuracy and simplicity both in principle and at implementation compared with the SCAPE-M method, the new method provides an option for atmospheric correction of MERIS data in inland turbid case II waters with applications aiming for chl-a estimation.

Oxygen-Dependent Auto-Oscillations of Water Luminescence Triggered by the 1264 nm Radiation

A 5-min exposure of air-saturated bidistilled water to low-intensity laser infrared radiation at the wavelength of the electronic transition of dissolved oxygen to the singlet state ((3)∑(g)(-)→ (1)Δ(g)) induces, after a long latent period, auto-oscillations of water luminescence in the blue-green region, which last many hours. Laser irradiation causes the accumulation of hydrogen peroxide, which depends on the concentration of dissolved oxygen. The auto-oscillations do not arise if water is irradiated beyond the oxygen absorption band and if the oxygen is removed from water. The wavelet transform analysis of luminescence records indicates that there are two characteristic periods of pulsations of about 300 and 1150 s. The results obtained suggest that auto-oscillations are triggered by photoinduced singlet oxygen (1)Δ(g), and this phenomenon is closely related to formation of hydrogen peroxide.

Modeling the impact of spectral sensor configurations on the FLD retrieval accuracy of sun-induced chlorophyll fluorescence

Chlorophyll fluorescence is related to photosynthesis and can serve as a remote sensing proxy for estimating photosynthetic energy conversion and carbon uptake. Recent advances in sensor technology allow remote measurements of the sun-induced chlorophyll fluorescence signal (Fs) at leaf and canopy scale. The commonly used Fraunhofer Line Depth (FLD) principle exploits spectrally narrow atmospheric oxygen absorption bands and relates Fs to the difference of the absorption feature depth of a fluorescensing and a non-fluorescensing surface. However, due to the nature of these narrow bands, Fs retrieval results depend not only on vegetation species type or environmental conditions, but also on instrument technology and processing algorithms. Thus, an evaluation of all influencing factors and their separate quantification is required to further improve Fs retrieval and to allow a reproducible interpretation of Fs signals. Here we present a modeling study that isolates and quantifies the impacts of sensor characteristics, such as spectral sampling interval (SSI), spectral resolution (SR), signal to noise ratio (SNR), and spectral shift (SS) on the accuracy of Fs measurements in the oxygen A band centered at 760 nm (O 2-A). Modeled high resolution radiance spectra associated with known Fs were spectrally resampled, taking into consideration the various sensor properties. Fs was retrieved using the three most common FLD retrieval methods, namely the original FLD method (sFLD), the modified FLD (3FLD) and the improved FLD (iFLD). The analysis investigates parameter ranges, which are representative for field and airborne instruments currently used in Fs research (e.g., ASD FieldSpec, OceanOptics HR, AirFLEX, AISA, APEX, CASI, and MERIS). Our results show that the most important parameter affecting the retrieval accuracy is SNR, SR accounts for ≤ 40% of the error, the SSI for ≤ 12%, and SS for ≤ 7% of the error. A trade-off study revealed that high SR can partly compensate for low SNR. There is a strong interrelation between all parameters and the impact of specific parameters can compensate or amplify the influence of others. Hence, the combination of all parameters must be considered by the evaluation of sensors and their potential for Fs retrieval. In general, the standard FLD method strongly overestimates Fs, while 3FLD and iFLD provide a more accurate estimation of Fs. We conclude that technical sensor specifications and the retrieval methods cause a significant variability in retrieved Fs signals. Results are intended to be one relevant component of the total uncertainty budget of Fs retrieval and have to be considered in the interpretation of retrieved Fs signals.

The spectral bandshape of the ν3 (1136 cm − 1) vibration of oxygen in silicon and dilute silicon–germanium alloys

At room temperature, the ν3 (1136 cm − 1) absorption band ofoxygen in silicon and Si1 − xGex alloys consists of dozens of components, masking the properties of the individualtransitions. Here, experimental data are presented for the evolution of theν3 band in the temperaturerange 0 < T < 300 K and thecomposition range 0 ≤ x ≤ 0.066. The vibrational potential for Si:O is developed to provide accurate fits to theabsorption data. The potential predicts properties consistent with publishedstudies, including hydrostatic stress experiments. Extending the model toSi1 − xGex allows the propertiesof the alloy-induced Oi-I, Oi-II and Oi-III components to be investigated accurately to higher values ofx than hitherto.The properties of Oi-I are understood as perturbations by Ge atoms of Si:O, andOi-III is rationalized in terms of off-axis movement of the O atom resultingfrom the nearby Ge atom. Challenges to theory are: the behaviour ofOi-II, understanding the strain fields generated by Ge atoms in Si, and the reduced coupling of theν2 andν3 modes with increasingamplitude in the ν2 mode.

Spectroscopic Measurement of Air Temperature

Optical dimensional measurements have to be corrected for the refractive index of air. The refractive index is conventionally calculated from parameters of ambient air using either Edlen or Ciddor equations or their modified versions. However, these equations require an accurate knowledge of ambient conditions and especially the temperature of air. For example, to reach an uncertainty of 10−7 in dimensions, the air temperature has to be known at ~100 mK level. This does not necessarily cause problems in a stable laboratory environment. However, if measurements are done outdoors or in an industrial environment, variations in temperature can be very rapid and local temperature gradients can cause significant error if not taken into account. Moreover, if the required distance is long, the temperature over the whole measurement path can be impractical or impossible to determine at sufficient temporal or spatial resolution by conventional temperature measurement techniques. The developed method based on molecular spectroscopy of oxygen allows both lateral spatial and temporal overlap of the temperature measurement with the actual distance measurement. Temperature measurement using spectroscopy is based on a line intensity ratio measurement of two oxygen absorption lines, previously applied for measurements of high temperatures in flames. The oxygen absorption band at 762 nm is a convenient choice for two-line thermometry since the line strengths are practical for short- and long-distance measurements and suitable distributed feedback lasers are commercially available. Measurements done on a 67 m path at ambient conditions demonstrate that the RMS noise of 22mK, or 7.5 × 10−5, near 293 K using 60 s measurement time can be achieved, which is to our knowledge the best reported resolution.

Detection of Vegetation Light-Use Efficiency Based on Solar-Induced Chlorophyll Fluorescence Separated From Canopy Radiance Spectrum

Photosynthetic light-use efficiency (LUE) is an important indictor of plant photosynthesis, but it is not yet assessable by remote sensing. The recent research on the separation of solar-induced chlorophyll fluorescence (ChlF) from the hyperspectral data indicates the possibility of detecting LUE. In this study, we presented a novel solution for monitoring LUE from hyperspectral data. Experiments at leaf level and canopy level were carried out on winter wheat (C3 plant functional type) on 18 April, 2008 and summer maize (C4 plant functional type) on 5 July, 2008 by synchronously measuring daily canopy radiance spectra and leaf or canopy LUE. The solar-induced chlorophyll fluorescence signals at 760 nm and 688 nm were separated from the reflected radiance spectra based on Fraunhofer lines in two oxygen absorption bands. The results showed that LUE was inversely related to the relative chlorophyll fluorescence. The leaf-level LUE models for winter wheat were built based on relative ChlF at bands of 688 nm (R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> =0.78) and 760 nm (R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> =0.64), whereas correlation coefficients of the canopy-level LUE models for summer maize on relative ChlF at the same bands were 0.63 and 0.77, respectively.

High resolution field spectroscopy measurements for estimating gross ecosystem production in a rice field

This study investigates the possibility of monitoring carbon fixation of a terrestrial ecosystem from high spectral resolution field spectroscopy measurements. Canopy radiance spectra were collected under clear sky conditions using high resolution spectrometers which made it possible to estimate sun-induced chlorophyll fluorescence at the oxygen absorption band O 2-A located at 760 nm ( F 760) as well as spectral vegetation indices. Spectral observations were collected in a rice field monitored with an eddy covariance (EC) flux tower measuring the net ecosystem exchange (NEE) of the crop. Estimation of gross ecosystem productivity (GEP) from remotely sensed data was based on the widely used light-use efficiency model (LUE), which states that carbon uptake is a function of the photosynthetically active radiation absorbed by vegetation (APAR) and light-use efficiency ( ɛ) which represents the conversion efficiency of energy to fixed carbon. Hyperspectral data were used to derive both the APAR and the ɛ term. Different versions of the LUE model were formalized and tested with EC fluxes during two growing seasons. We started using a LUE model in which ɛ is held constant and remote sensing data are used to estimate APAR. We then investigated the improvements in GEP modelling provided by the partitioning between photosynthetic (PV) and non-photosynthetic (NPV) components of vegetation in APAR estimation, holding ɛ constant. The use of spectral indices related to APAR PV instead of APAR resulted in an improvement in midday GEP estimation of about 50% with respect to the basic LUE model, average root mean square error in cross-validation (RMSE cv) of the model class from 9.69 to 4.49 μmol CO 2 m −2 s −1. Afterwards, we tested the use of the apparent fluorescence yield (Fy * 760) and the scaled Photochemical Reflectance Index (sPRI) to derive ɛ. Modelling ɛ further improved the estimation of GEP up to an RMSE cv of 3.81 μmol CO 2 m −2 s −1 using Fy * 760 and the MERIS terrestrial chlorophyll index (MTCI) and 3.67 μmol CO 2 m −2 s −1 using sPRI and F 760 to estimate ɛ and APAR PV, respectively.

Remote sounding of atmospheric pressure profile from space, part 1: principle

The molecular oxygen absorption band near 0.762 µm can be used for remote sounding of atmospheric pressure profiles. Atmospheric O2 absorption, atmospheric molecular multi-scattering, extinction of atmospheric aerosols, bi-reflection at the earth surface, the atmospheric refractive effect and the global curvature are taken into account to establish an atmospheric radiation transfer equation. By means of an accurate O2 atmospheric transmittance model and a mean atmospheric transmittance model the remote sounding equation of surface pressure from space suitable to clear sky field of view is derived. At last, a pure physical retrieval method is given and the atmospheric pressure profile can be deduced.

Performance of Spectral Fitting Methods for vegetation fluorescence quantification

The Fraunhofer Line Discriminator (FLD) principle has long been considered as the reference method to quantify solar-induced chlorophyll fluorescence ( F) from passive remote sensing measurements. Recently, alternative retrieval algorithms based on the spectral fitting of hyperspectral radiance observations, Spectral Fitting Methods (SFMs), have been proposed. The aim of this manuscript is to investigate the performance of such algorithms and to provide relevant information regarding their use. FLD and SFMs were used to estimate F starting from Top Of Canopy (TOC) fluxes at very high spectral resolution (0.12 nm) and sampling interval (0.1 nm), exploiting the O 2-B (687.0 nm) and O 2-A (760.6 nm) atmospheric oxygen absorption bands overlapping the fluorescence emissions at the red and far-red spectral window. Specific parameters affecting FLD and SFM performances are investigated and the accuracy of F estimation of the two methods is compared. The problem related to the lack of independent measurements of F at canopy level, which prevents the direct assessment of F estimation accuracy with actual measurements, is overcome in this study by using a modeled database of TOC reflectance spectra. In order to compute accuracy figures valid for operative applications the simulated spectra were perturbed by the addition of radiometric noise. An investigation was conducted to determine the best FLD channel configuration; it showed that violation of FLD assumptions results in a positive bias in F estimation at both oxygen absorption bands that cannot be avoided even at the high spectral resolution considered. SFMs were shown to be more accurate than FLD under any noise configuration considered.

Oxygen Diffusion in Si&lt;sub&gt;1-x&lt;/sub&gt;Ge&lt;sub&gt;x&lt;/sub&gt; Alloys

The measurements of stress induced dichroism on oxygen absorption band near 1107 cm-1 in Si1-xGex compounds and subsequent kinetics of the dichroism recovery upon isothermal annealing have been carried out. It has been found that the magnitude of introduced by uniaxial stress dichroism decreases with increasing Ge content. Two components in the dichroism annealing kinetics have been found. On the basis of studying absorption spectra of samples under investigations it was assumed that two components in relaxation correspond to the diffusion of oxygen being in a different nearest environment: the one component corresponds to oxygen surrounded by silicon atoms and the second one to the oxygen the neighbour of which is Ge atom. Diffusivity for each of the components has been determined. It has been shown that the diffusivity of oxygen that is in both of these configurations decreases with increasing Ge content.