Spectral Absorption Features Research Articles

Evidence for diurnally varying enrichment of heavy oxygen in Mars atmosphere

Terrestrial groundbased spectroscopy of Mars at subsolar latitude in October 2007 (southern summer, Mars year 28) reveals variability in the depth of a spectral absorption feature from a carbon dioxide isotopologue, 16O12C18O (‘628 CO2’), which correlates with increasing surface temperature in the early afternoon of the Martian sol. The correlation suggests a fractionation process that depletes isotopically heavy CO2 from the atmosphere by surface adsorption at night and restores atmospheric enrichment during the day through thermal desorption. Measurements reported here yield a depleted condition at noon, with 18O depleted to −92 ± 23‰ relative to a terrestrial isotopic standard (VSMOW, Vienna Standard Mean Ocean Water), increasing to +71 ± 18‰ at 13:19 LST, over a temperature increase from 266.9 K to 275.4 K. The average is +9 ± 14‰, consistent with results from landers and remote spectroscopy that averaged data collected over a broad range of daylight local times to obtain an average close to the terrestrial standard. Past measurements of CO2 isotopologues have been inconsistent with each other and in some cases inconsistent with predicted enrichment in heavy isotopes, with some measurements even slightly depleted in heavy isotopes. Local solar time of a measurement thus may skew this important constraint on estimating the density of the primordial atmosphere, although seasonal polar temperature variation also may have a substantial influence.

Suppressing elaton drifts

suppressing elaton drifts

Effect of solvent on the electronic absorption spectral properties of Ni(II) and Cu(II)-complexes of some mixed β-octasubstituted-meso-tetraphenylporphyrins

A series of mixed β-substituted porphyrins, 2,3,12,13-tetrakis(bromo/cyano/methyl)-5,7,8,10,15,17,18,20-octaphenylporphinatonickel(II)/copper(II), MOPPX4s (X = Br, CN and CH3; M = Ni(II) and Cu(II)) were examined in 24 different solvents with varying polarity. Among the porphyrins, MOPP(CN)4 show enhanced solvent dependent optical absorption spectral features relative to other porphyrins, MOPPX4 (X = Br and CH3) and MTPPs. Although, MOPP(CN)4 (M = Ni(II) and Cu(II)) have higher electron deficiency due to electron withdrawing β-cyano groups, comparable solvent dependent absorption spectral features and opposite trend in their shift of bands relative to the corresponding MTPPBr8 were observed. The large red-shift of the absorption bands of Cu(II) and Ni(II)-mixed substituted porphyrins in polar solvents or nitrogenous bases has been suggested to the destabilization of the HOMO (b2) relative to b1 (HOMO) level due to axial ligation of the polar solvents or nitrogenous bases with the core metal ions. The greater affinity of the core metal ions towards coordinating solvents or nitrogenous bases has been attributed to the electron deficient nature of the porphyrin π-system and follow the order: MOPP(CN)4 > MOPPBr4 > MOPP(CH3)4 due to inductive/resonance effect of β-substituents rather than the nonplanarity of the porphyrin ring.

Remote detection of cyanobacteria blooms in an optically shallow subtropical lagoonal estuary using MODIS data

Widespread and persistent Ecosystem Disruptive Algal Blooms dominated by marine picocyanobacteria (Synechococcus) commonly occur in the subtropical lagoonal estuary of Florida Bay (U.S.A). These blooms have been linked to a decline in natural sheet flow over the past century from upstream Everglades National Park. Remote sensing algorithms for monitoring cyanobacteria blooms are highly desired but have been mainly developed for freshwater and coastal systems with minimal bottom reflectance contributions in the past. Examination of in situ optical properties revealed that Synechococcus blooms in Florida Bay exhibit unique spectral absorption and reflectance features that form the basis for algorithm development. Using a large, multi-year match-up dataset (2002–2012; n = 682) consisting of in situ pigment concentrations and Moderate Resolution Imaging Spectroradiometer (MODIS) Rayleigh-corrected reflectance (Rrc(λ)), classification criteria for detecting cyanobacteria blooms with chlorophyll-a concentrations (Chl-a) ~5–40 mg m−3 were determined based on a new approach to combine the MODIS Cyanobacteria Index, CIMODIS, and spectral shape around 488 nm, SS(488). The inclusion of SS(488) was required to prevent false positive classifications in seagrass-rich, non-bloom waters with high bottom reflectance contributions. 75% of cyanobacteria blooms were classified accurately based on this modified CI approach with <1% false positives. A strong correlation observed between cyanobacteria bloom in situ Chl-a and CIMODIS (r2 = 0.80, n = 32) then allowed cyanobacterial chlorophyll-a concentrations (ChlCI) to be estimated. Model simulations and image-based analyses showed that this technique was insensitive to variable aerosol properties and sensor viewing geometry. Application of the approach to the entire MODIS time-series (2000–present) may help identify factors controlling blooms and system responses to ongoing management efforts aimed at restoring flow to pre-drainage conditions. The method may also provide insights for algorithm development for other lagoonal estuaries that experience similar blooms.

Mapping Listvenite Occurrences in the Damage Zones of Northern Victoria Land, Antarctica Using ASTER Satellite Remote Sensing Data

Listvenites normally form during hydrothermal/metasomatic alteration of mafic and ultramafic rocks and represent a key indicator for the occurrence of ore mineralizations in orogenic systems. Hydrothermal/metasomatic alteration mineral assemblages are one of the significant indicators for ore mineralizations in the damage zones of major tectonic boundaries, which can be detected using multispectral satellite remote sensing data. In this research, Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) multispectral remote sensing data were used to detect listvenite occurrences and alteration mineral assemblages in the poorly exposed damage zones of the boundaries between the Wilson, Bowers and Robertson Bay terranes in Northern Victoria Land (NVL), Antarctica. Spectral information for detecting alteration mineral assemblages and listvenites were extracted at pixel and sub-pixel levels using the Principal Component Analysis (PCA)/Independent Component Analysis (ICA) fusion technique, Linear Spectral Unmixing (LSU) and Constrained Energy Minimization (CEM) algorithms. Mineralogical assemblages containing Fe2+, Fe3+, Fe-OH, Al-OH, Mg-OH and CO3 spectral absorption features were detected in the damage zones of the study area by implementing PCA/ICA fusion to visible and near infrared (VNIR) and shortwave infrared (SWIR) bands of ASTER. Silicate lithological groups were mapped and discriminated using PCA/ICA fusion to thermal infrared (TIR) bands of ASTER. Fraction images of prospective alteration minerals, including goethite, hematite, jarosite, biotite, kaolinite, muscovite, antigorite, serpentine, talc, actinolite, chlorite, epidote, calcite, dolomite and siderite and possible zones encompassing listvenite occurrences were produced using LSU and CEM algorithms to ASTER VNIR+SWIR spectral bands. Several potential zones for listvenite occurrences were identified, typically in association with mafic metavolcanic rocks (Glasgow Volcanics) in the Bowers Mountains. Comparison of the remote sensing results with geological investigations in the study area demonstrate invaluable implications of the remote sensing approach for mapping poorly exposed lithological units, detecting possible zones of listvenite occurrences and discriminating subpixel abundance of alteration mineral assemblages in the damage zones of the Wilson-Bowers and Bowers-Robertson Bay terrane boundaries and in intra-Bowers and Wilson terranes fault zones with high fluid flow. The satellite remote sensing approach developed in this research is explicitly pertinent to detecting key alteration mineral indicators for prospecting hydrothermal/metasomatic ore minerals in remote and inaccessible zones situated in other orogenic systems around the world.

DL-3-Aminoisobutyric acid: vibrational, NBO and AIM analysis of N–H⋯O bonded-zwitterionic dimer model

A zwitterionic dimer model constructed of inter-molecular –N–H⋯O bonding has been proposed for the solid sample of DL-3-Aminoisobutyric acid consistent with IR absorption and Raman spectral features measured in the 3500–400/50 cm−1. This zwitterionic dimer model in water as solvent has been computed at B3LYP/6–311++G(d,p) and B3LYP-D3/6–311++G(d,p) levels including Grimme's dispersion correction associated with the –N–H⋯O interaction and SCRF-SMD method. Of the several possible monomer and dimer conformational structures, the most stable dimer constructed of two zwitterion monomer units has produced vibrational modes due to the –NH3+ cation and –CO2‾ anion involved in the –N–H⋯O bonding in fair agreement with the observed broad but composite IR modal features near the 3500–2000 cm−1. Except for the frequency of asymmetric stretching mode of the –NH3+ cation, its symmetric and bending modes agree with the observed values. As for the –CO2‾ anion, the frequencies of all of its modes are in good agreement with the experiment. Natural bond orbital (NBO), molecular electrostatic potential (MEP), atoms-in-molecules (AIM) and non-covalent interaction (NCI) analyses have been used to understand electronic characterization of the –N–H⋯O bonding.

Spectral Absorption Feature Analysis for Finding Ore: A Tutorial on Using the Method in Geological Remote Sensing

Geologists have been instrumental in shaping Earth observation satellite missions; likewise, geology has been the subject of many remote sensing studies [1]. Applications of optical remote sensing in geology date back to some early studies using the Earth Resources Technology Satellite-1 , the predecessor of the Landsat satellite program [2]. In the 1980s, the seventh channel in the short-wave infrared (SWIR) of the Landsat thematic mapper program was added, as a result of spectroscopic mineral studies by geologists [58]. A subsequent satellite-borne instrument, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), launched in 1999, had specific bands in the SWIR and thermal infrared dedicated to mapping mineral groups [3].

Near- to mid-infrared spectroscopy of the heavily obscured AGN LEDA 1712304 with AKARI/IRC

Context. Although heavily obscured active galactic nuclei (AGNs) have been found by many observational studies, the properties of the surrounding dust are poorly understood. Using AKARI/IRC spectroscopy, we discovered a new heavily obscured AGN in LEDA 1712304 which shows a deep spectral absorption feature due to silicate dust. Aims. We study the infrared (IR) spectral properties of circumnuclear silicate dust in LEDA 1712304. Methods. We performed IR spectral fitting, considering silicate dust properties such as composition, porosity, size, and crystallinity. Spectral energy distribution fitting was also performed on the flux densities in the UV to submillimeter range to investigate the global spectral properties. Results. The best-fit model indicates 0.1 μm-sized porous amorphous olivine (Mg2xFe2−2xSiO4; x = 0.4) with 4% crystalline pyroxene. The optical depth is τsil ∼ 2.3, while the total IR luminosity and stellar mass are estimated to be LIR = (5 ± 1)×1010 L⊙ and Mstar = (2.7 ± 0.8)×109 M⊙, respectively. In such low LIR and Mstar ranges, there are few galaxies that show such a large τsil. Conclusion. The silicate dust in the AGN torus of LEDA 1712304 has properties that are notably similar to those in other AGNs overall, but slightly different in the wing shape of the absorption profile. The porosity of the silicate dust suggests dust coagulation or processing in the circumnuclear environments, while the crystallinity suggests that the silicate dust is relatively fresh.

Identification of inorganic oxidizing salts in homemade explosives using Fourier transform infrared spectroscopy

Recently, inorganic low explosives, such as pyrotechnic composition, black powder, and ammonium nitrate, are commonly used in improvised explosive devices (IEDs) by the rioter or terrorists since these energetic materials can be obtained easily and legally from civilian markets. Identification of inorganic oxidizing salts in these homemade explosives, including nitrates, chlorates, and perchlorates, is a necessary procedure for forensic investigators to provide criminal evidences. In this article, Fourier transform infrared (FTIR) spectroscopy was used to discriminate NO3-, CO32-, ClO3-, ClO4-, SO42-, and NH4+, whose characteristic absorption bands were explained by vibration modes of the covalent bonds. Then the spectral absorption features of nitrate salts with monovalent or divalent cations were discussed. Furthermore, it was studied whether nitrates or perchlorates can be unequivocally distinguished with the presence of carbonate and sulfate impurities through FTIR technique. Finally, the feasibility of this method was verified through an analytical case of homemade explosives.

Fire detection and temperature retrieval using EO-1 Hyperion data over selected Alaskan boreal forest fires

Infrared imaging spectrometers are used to map and characterize wildland fire based on their sensitivity to fire-emitted thermal radiation and ability to resolve spectral emission or absorption features. There is a general paucity of research on the use of space-borne imaging spectroscopy to study active fires in the North American boreal forest. We used hyperspectral data acquired by the Hyperion sensor on the EO-1 satellite over three wildfires in Alaska’s boreal forest to evaluate three fire detection methods: a metric to detect an emission feature from potassium emitted by biomass burning; a continuum-interpolated band ratio (CIBR) that measures the depth of a carbon dioxide absorption line at 2010 nm; and the Hyperspectral Fire Detection Index (HFDI), which is a normalized difference index based on spectral radiance in the short-wave infrared range. We found that a modified version of the HFDI produces a well-defined map of the active fire areas. The CO2 CIBR, though affected by sensor noise and smoke, contributes a slight improvement to the fire detection performance when combined with HFDI-type indices. In contrast, detecting a fire signal from potassium emission was not reliably possible in a practically useful way. We furthermore retrieved fire temperatures by modeling the at-sensor radiance as a linear mixture of two emitted and two reflected spectral radiance endmembers. High-temperature fire areas (the high-intensity fire front, modeled at 800–900 K) and low-temperature combustion (residual fire at 500–600 K), were mapped. High-temperature burning areas as small as half a percent of a Hyperion pixel (approx. 5 m2) were detectable. These techniques are of potential interest for fire characterization in the boreal areas of the circumpolar North using current and future satellite-borne imaging spectrometers.

Mitigating the effects of granular scattering using cepstrum analysis in terahertz time-domain spectral imaging.

Terahertz (THz) imaging is a widely used technique in the study and detection of many chemicals and biomolecules in polycrystalline form because the spectral absorption signatures of these target materials often lie in the THz frequencies. When the size of dielectric grain boundaries are comparable to the THz wavelengths, spectral features can be obscured due to electromagnetic scattering. In this study, we first investigate this granular scattering effect in identification of chemicals with THz spectral absorption features. We then will propose a signal processing technique in the so-called “quefrency” domain to improve the ability to resolve these spectral features in the diffuse scattered THz images. We created a pellet with α-lactose monohydrate and riboflavin, two biologically significant materials with well-known vibrational spectral resonances, and buried the pellet in a highly scattering medium. THz transmission measurements were taken at all angles covering the half focal plane. We show that, while spectral features of lactose and riboflavin cannot be distinguished in the scattered image, application of cepstrum filtering can mitigate these scattering effects. By employing our quefrency-domain signal processing technique, we were able to unambiguously detect the dielectric resonance of lactose in the diffused scattering geometries. Finally we will discuss the limitation of the new proposed technique in spectral identification of chemicals.

Partial sub-pixel and pixel-based alteration mapping of porphyry system using ASTER data: regional case study in western Yazd, Iran

ABSTRACT This study uses remote sensing image-processing to enhance recognition of areas with mineral abundance halo, which can be associated with porphyry mineralisation of the Urumieh-Dokhtar Magmatic Belt (UDMB) in western Yazd. Granitoid intrusions of Oligocene-Miocene age in UDMB hosts the most important Porphyry Copper Deposits (PCDs) of Iran such as Darezereshk and Aliabad PCDs. Diagnostic spectral absorption features of six shortwave infrared (SWIR) and three visible and near-infrared (VNIR) bands of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data were applied to determine the alteration minerals and their abundance. In this research reflectance data from various representative alteration types throughout the study area were measured by the FieldSpec-3 spectroradiometer and applied for mapping minerals. Different remote sensing analytical techniques, including the Principal Component Analysis (PCA), band ratio, relative absorption band depth, and MTMF, were applied to enhance mapping the alteration minerals. Field works including rock sampling, petrography and field spectroradiometer followed up the alteration mapping. Field observation implies that, the vein-type mineralisation above the cupola of this porphyry system is preserved in the western part, although it was eroded in the eastern area. Consequently, PCDs potential is expected to be higher in the western area.

Plastic solid waste identification system based on near infrared spectroscopy in combination with support vector machine

Abstract In this paper, identification system of plastic solid waste (PSW) based on near-infrared (NIR) reflectance spectroscopy in combination with Support Vector Machine (SVM) was presented. A device applied to obtain NIR spectra of plastics in the detection platform was developed. After pre-processing (normalized, 1st derivative and smooth), the repeatability of spectral absorption features was improved, which would assist the identification. A “principal component analysis (PCA) SVM” identification method was proposed to identify polypropylene (PP), polystyrene (PS), polyethylene (PE), poly(methyl methacrylate) (PMMA), acrylonitrile butadiene styrene (ABS) and polyethylene terephthalate (PET) among plastics, and its identification accuracy can reach 97.5%. The type of samples could clearly be identified and the shape of samples could also be roughly discerned. It is clearly shown that this system can achieve good identification results while reducing costs considerably, which has great potential in industrial recycling.

Spectroscopic investigations of dysprosium ions doped oxy chloro boro tellurite glasses for visible photonic device applications

Spectroscopic properties of oxy chloro boro tellurite glasses (OCBT) doped with varying concentration of dysprosium ions were studied using X-ray Diffraction (XRD), Fourier transform infrared (FT-IR), Raman, absorption, excitation and photoluminescence (PL) spectral studies. Judd-Ofelt (J-O) theory has been applied to the recorded absorption spectral features to evaluate various radiative parameters for the prominent fluorescent levels of Dy3+ ions doped OCBT glasses. Under 350 nm excitation, intense blue and yellow emissions at 483 nm (4F9/2 → 6H15/2) and 575 nm (4F9/2 → 6H13/2) were observed respectively and show concentration quenching at 1 mol% of Dy3+ ions in OCBT glasses. Dexter theory applied to the PL spectra reveals dipole-dipole interaction responsible for energy transfer between the doped Dy3+ ions to show concentration quenching in the prepared glasses. The yellow to blue (Y/B) intensity ratio, CIE chromaticity coordinates and color correlated temperatures (CCT) have been evaluated from the PL spectra for all the prepared glasses. The emission cross-sections, branching ratios and quantum efficiency evaluated for the OCBT glasses confirm the suitability of Dy3+ doped OCBT glasses for visible photonic device applications.

Structural, optical and NIR studies of Er3+ ions doped bismuth boro tellurite glasses for luminescence materials applications

Abstract Bismuth Boro Tellurite (BiBT) glasses doped with Er3+ ions (i.e., Er3+ = 0.1, 0.5, 1.0, 1.5, 2.0, 2.5 mol %) were prepared by using melt quenching technique and their structural, optical absorption, emission and up-conversion properties were investigated using XRD, Raman, absorption, emission and decay spectral studies. The oscillator strengths measured from the absorption spectral features were subjected to Judd-Ofelt theory to understand the radiative properties possessed by the as prepared glasses. The titled glasses excited under 379 nm exhibited green luminescence at 547 nm (4S3/2 → 4I15/2). Upon pumping with a laser diode of 980 nm (NIR), a broad NIR emission at around 1572 nm (4I13/2 → 4I15/2) was observed for which stimulated emission cross-section (σse), effective band width (Δλp), gain band width (σse × Δλp) and optical gain (σse × τR) parameters were evaluated. The up-conversion luminescence shown by these glasses has been analysed to understand the utility of these glasses as up-conversion lasers. Among all the as prepared glasses, 1 mol% of Er3+ ions doped BiBT glass exhibits better radiative properties compared to other glasses. The gain cross-section of the 1 mol% of Er3+ ions doped BiBT glass was derived using absorption cross-section (σa) and emission cross-section (σe) for different values of population inversion (γ). The Decay spectral features recorded under 980 nm excitation were used to measure the experimental lifetimes (τexp) and quantum efficiencies. All the aforementioned studies revealed that the Er3+ ions doped BiBT glasses are quite suitable to fabricate optoelectronic devices in visible green and NIR regions.

Electronically Divergent Triscyclometalated Iridium(III) 2-(1-naphthyl)pyridine Complexes and Their Application in Three-Component Methoxytrifluoromethylation of Styrene

A systematic study of the photophysical and electrochemical properties of triscyclometalated homoleptic iridium(III) complexes based on 2-(1-naphthyl)pyridine (npy) ligands is presented. A systematic investigation of ligand substitution patterns showed an influence on the lifetime of the excited state, with slight changes in the absorption and emission spectral features. Specifically, the emission lifetime of a complex of an npy ligand substituted with a strongly electron-withdrawing trifluoromethyl group was longer than that of the corresponding complex with the electronically nonperturbed ligand (3.7 μs versus 1.5 μs). Electronically complementary ligands and complexes with ­orthogonal configurations showed slightly shorter excited state lifetimes compared with unsubstituted npy (1.4–3.0 μs). All complexes displayed reversible or quasireversible redox-couple processes, with the complex of the trifluoromethylated ligand showing the highest ground-state oxidation potential E1/2 ox [Ir(III)/Ir(IV) = 0.95 V vs. SCE in CH2Cl2]. This study showed that these complexes can be used as efficient photoredox catalysts, as demonstrated by their application in a regioselective methoxytrifluoromethylation in which the npy complexes showed equal or better performance compared with the archetypical photo­redox catalyst tris[2-phenylpyridinato]iridium(III).

Spectroscopic studies of Dy3+ ions doped barium lead alumino fluoro borate glasses

Barium lead alumino fluoro borate (BaPbAlFB) glasses doped with Dy3+ ions were prepared by using melt quenching technique and characterized using various spectroscopic techniques to understand their usage in photonic devices. The SEM and EDX spectral studies were performed on the as prepared glasses to understand the glassy nature and elemental analysis respectively. The weight loss in the BaPbAlFB glass has been studied by the TGA. Judd-Ofelt (J-O) theory has been applied to the measured oscillator strengths of the absorption spectral features to evaluate radiative parameters for the prominent emission transitions of Dy3+ ions in BaPbAlFB glasses. The photoluminescence (PL) spectral measurements show concentration quenching beyond 1.0 mol% of Dy3+ ions in the as prepared glasses. The decay profiles observed for higher concentration of Dy3+ ions in these glasses are well fitted to Inokuti-Hirayama (IH) model to understand the energy transfer mechanism involved in the as prepared glasses. The experimental lifetimes (τexp) measured from the decay spectral features are correlated with radiative lifetime (τR) values to understand the quantum efficiency (η) of the as prepared glasses. From the PL spectra, colorimetric parameters such as CIE coordinates, correlated color temperature (CCT) and yellow-to-blue (Y/B) intensity ratios have been estimated to understand the usage of these glasses in photonic devices such as white LEDs and lasers.

β-Functionalized Dibenzoporphyrins with Mixed Substituents Pattern: Facile Synthesis, Structural, Spectral, and Electrochemical Redox Properties.

A new series of mixed β-substituted dibenzoporphyrins were synthesized, and the effect of β-substitution on the spectral and electrochemical redox properties of the macrocycle was elucidated. The synthetic route to β-tetrasubstituted dibenzoporphyrins begins with the regioselective bromination of NiTPP(Benzo)2 to afford NiTPP(Benzo)2Br4, followed by Pd catalyzed coupling reaction to access NiTPP(Benzo)2(R)4 (R = phenyl (Ph) and phenylethynyl (PE)). Synthesized benzoporphyrins exhibited red-shifted absorption spectral features with tunable redox properties. These benzoporphyrins displayed pronounced electronic effects of β-substituents on the macrocyclic skeleton. NiTPP(Benzo)2(PE)4 exhibited the lowest HOMO-LUMO gap among the series due to extended π-conjugation. Intrestingly, metal-centered oxidation of Ni(II)/Ni(III) was observed for NiOPP(Benzo)2 and NiOPP(Benzo)Br2 after an initial conversion of the neutral porphyrin to its dicationic form under electrochemical conditions.

Detection of heavy hydrocarbon plumes (Ethane, propane and Butane) using airborne longwave (7.6–13.5 μm) infrared hyperspectral data

Recent developments in the detection of gaseous hydrocarbons (HCs) through remote sensing are focused on the characterization of methane (CH4). Basically, there is no research related to remote sensing of other heavier HC gases (ethane: C2H6, propane: C3H8, butane: C4H10), whether derived from natural seeps or from leaks at various stages of production, transportation and storage of petroleum resources. Just as methane; ethane, propane and butane have typical spectral signatures in the longwave infrared region (7.6–13.5 μm), which potentiates their detection by means of airborne hyperspectral sensors (nadir or oblique measurements) or by fixed, ground-based hyperspectral and ultraspectral sensors (horizontal/profile measurements). In this context, the aim of this work is to evaluate the detection limits of the Spatially-Enhanced Broadband Array Spectrograph System (SEBASS) for the identification of ethane, propane and butane in gaseous emissions under controlled leaks. Due to the low content of heavy HCs (C2-C4) in the tested mixtures, they were only identified in plumes derived from sources with emission rates equal to or greater than 1000 standard cubic feet per hour (scf/h). Despite the complex mixture comprised in the plume, the spectral absorption features of each HC allowed their individualization in the SEBASS imagery. The methodology introduced here demonstrates that airborne hyperspectral thermal sensors can identify the different types of HC gases composing the plume, strengthening the possibilities for the evaluation of gas leaks from petroleum installations and natural seeps, assisting in exploration campaigns and diminishing the risk for technological accidents in industrial plants.

Realization of a infrared detector free of bandwidth limit based on quartz crystal tuning fork

A new type of photoelectric detector based on a standard quartz crystal tuning fork (QCTF) with resonant frequency of ∼32 kHz is developed for infrared spectroscopy applications. Analogous to the photoelectric effect of traditional semiconductor detectors, we utilize the piezoelectric effect of the QCTF to gauge the light intensity. To demonstrate this technique, the spectral absorption features of C2H2 molecule have been recorded and compared with a commercial mercury cadmium-telluride (MCT) detector. The proposed detection technique may pave a new way towards developing a new type of photodetector without bandwidth limit and complicated cryogenic cooling,