Overtone Absorption Bands Research Articles

Determination of glucose concentration in a scattering medium based on selected wavelengths by use of an overtone absorption band.

A method and device for measuring glucose concentration in a scattering medium have been developed. A spectral range of 800-1800 nm is considered for wavelength selection because of its deeper penetration into biological tissue and the presence of a glucose absorption band. An algorithm based on selected wavelengths is proposed to minimize interference from other components. The optimal distance between the light source and the detector for diffuse reflectance measurement minimizes the influence of medium scattering. The proposed algorithm and measuring device are tested with a solution containing milk with added glucose. Glucose concentrations between 0 and 2000 mg/dl are determined with a correlation coefficient of 0.977. We also investigate the influence of concentration variations of other substances such as water, hemoglobin, albumin, and cholesterol when they are mixed in a scattering medium.

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

A Fourier transform interferometer was used to record the slit-jet cooled overtone absorption spectrum of 12C2H4 between 3900 and 7900cm−1, at a spectral resolution of 0.02cm−1 and a rotational temperature of 53 K. Some 17 bands were observed and rotationally analysed, leading to effective vibration—rotation constants for all upper states. Coriolis perturbations were identified and refined vibration—rotation constants were produced for seven upper states as well as for 12 Coriolis interacting dark states. Symmetry conventions different from those of the previous literature are selected in the present work.

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

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

Two Photon Excitation Spectrum of a Twisted Quadruple Bond Metal−Metal Complex

Two Photon Excitation Spectrum of a Twisted Quadruple Bond Metal−Metal Complex

Absorption measurements of the second overtone band of NO in ambient and combustion gases with a 18-µm room-temperature diode laser

We describe the development of a room-temperature diode sensor for in situ monitoring of combustion-generated NO. The sensor is based on a near-IR diode laser operating near 1.8 mum, which probes isolated transitions in the second overtone (3, 0) absorption band of NO. Based on absorption cell data, the sensitivity for ambient atmospheric pressure conditions is of the order of 30 parts in 10(6) by volume for a meter path (ppmv-m), assuming a minimum measurable absorbance of 10(-5). Initial H(2) -air flame measurements are complicated by strong water vapor absorption features that constrain the available gain and dynamic range of the present detection system. Preliminary results suggest that detection limits in this environment of the order of 140 ppmv-m could be achieved with optimum baseline correction.

Simple Near-Infrared Spectrometric Sorption-Based Vapor Sensor

A new class of near-IR sensors has been devised which relies on spectroscopic near-IR detection of analytes sorbed on a preconcentrating layer. The new sensors furnish both qualitative and quantitative information by detection of molecular vibrational overtone and combination absorption bands and by measurement of changes in the scattering of the silica-gel medium. A silica-gel thin-layer chromatography (TLC) plate was used as the adsorbent medium. This method is responsive to vapors ranging from water to carbon tetrachloride. Ethyl- and octylderivatized TLC plates were also tested and generally exhibited a weaker response and different spectral features than the original plate. The optical nature of these sensors opens up the possibility of remote analysis by coupling the technique with fiber optics and/or near-IR light-emitting diodes and lasers. Detection limits ranged from 4.1 to 210 ppm by volume. Polar compounds able to hydrogen bond to the surface exhibited lower detection limits than nonpolar compounds.

Near-ir spectroscopy and the photospheres of embedded ysos

We present a study of weak near-IR absorption lines in 44 low luminosity YSOs. Using a spectral resolution of ~ 1000 most Class II sources show CO overtone absorption bands of varying strength in the K window, whether they have optical counterparts or not. Class I sources tend to show featureless 2 μm continua even though a S/N > 100 was achieved. High resolution (R=17000) echelle spectra were also obtained for a sub-sample of YSOs. Most show an unresolved 12CO(2–0) bandhead, which when combined with inferred CO excitation temperatures and optical depths clearly points to a photospheric rather than a disk origin for the bands. They also show that embedded Class Its are not rapidly rotating.

Gas sensing with lambda = 1.57 micrometer distributed feedback laser diodes using overtone and combination band absorption

Spectral measurements of the v 1 + v 2 + v 3 combination absorption band of H 2 S were made over a 10-nm wavelength range around 1.57 m with two tunable distributed feedback (DFB) laser diodes. Targeting the strongest observed H 2 S absorption feature, a detection limit at atmospheric pressure of 50 ppm/m is indicated from the measured detectivity at higher concentration. We also probed the 2 v 1 + 2 v 2 + v 3 overtone and combination absorption band of CO 2 and investigated the dependence of absorption linewidth on pressure and assessed its implications for expected low-detection limits. These results demonstrate the utility of DFB laser diodes for industrial applications in the area of toxic and trace gas monitoring.

Single-crystal infrared characterization of ternary sulfides

Abstract Infrared spectra in the 2.0–23.5 μm region have been obtained for single crystals of KInS2, CaY2S4, and SrY2S4. Diamond, ZnS, GaP, and CdS crystals served as reference samples. The observed frequencies of the first overtone (or two-phonon) bands were used to evaluate the practical optical cut-offs arising from the second overtone (or three-phonon) absorption bands that occur in the long-wavelength (8–12 μm) region. The resulting transparency limits of bulk ceramics of KInS2, CaY2S4, and SrY2S4 are predicted to occur near 9.7, 11.7, and 11.4 μm, respectively, and are discussed in relation to the observed crystal structures.

Infrared spectra of CF 3CCH complexes with various proton acceptors in liquid argon

Fundamental and overtone absorption bands of CF 3CCH and its complexes with ethers (“non-linear” complexes) and with amines (“linear” complexes) have been studied in dilute solutions in liquefied argon at 90 K. IR absorption spectra were studied in the region 7000-400 cm −1 with resolution 0.5 cm −1 at 3000 cm −1 and optical path 1.4–163 cm. The frequencies and probabilities of vibrational transitions have been obtained for CF 3CCH (50 bands), for non-linear complexes (25 bands) and for linear complexes (15 bands). Splitting of the E symmetry bands of the non-linear complex has been observed. The complex profile of CH-absorption bands are in agreement with the theoretical approach which considers a complex as a molecule with several low-frequency modes.

2- m CO overtone absorption in young stellar objects

12CO overtone absorption bands have been detected in five of 10 low-luminosity YSOs studied in the Ophiuchus cloud core. The majority of those showing absorption have class II spectral energy distributions. The majority of the class I objects show no spectral features at all. If the bands are assumed to be photospheric in origin, then the results can be understood as a decrease in veiling by an IR continuum excess as the sources evolve from class I to class II.

Properties of the gas and stellar content of the superluminous galaxy NGC 6240

view Abstract Citations (87) References (24) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Properties of the Gas and Stellar Content of the Superluminous Galaxy NGC 6240 Lester, D. F. ; Harvey, P. M. ; Carr, J. Abstract We present H and K band spectra at resolving powers between 160 and 625 of the superluminous galaxy NGC 6240. Our data show a rich spectrum of molecular hydrogen emission lines and [Fe II]. CO first and second overtone absorption bands characteristic of cool stars are observed, indicating that the near-infrared light from the galaxy is not substantially diluted with nonthermal emission from the active nuclei. Weak Brγ is detected in the source, and the inference that the ratio of ionizing radiation-to-total luminosity in NGC 6240 is very much lower than in star-forming regions is confirmed, as is the relatively small extinction to the near-infrared emitting region. With the exception of one line, the molecular hydrogen spectrum is well fitted by shock models, with kinetic temperatures in the gas ranging from 1300 to 2800 K. About 1% of the molecular gas in the galaxy appears to be shock heated. Using computed shock models, the strength of the 1.64 micron [Fe II] suggests that much of this ionized hydrogen may be due to the shocks themselves, rather than OB stars. The velocity dispersion of the molecular hydrogen emitting gas is identical to that of the shock-ionized gas that is seen in the optical part of the spectrum, suggesting that they are coextensive. Both continuum and 1-0 S(1) line emission of H_2_ are spatially resolved at the kiloparsec level. The physical size and continuum luminosity are consistent with a nuclear bulge population in two merged galaxies that are close to the bright end of the luminosity function for normal late-type spirals. The extent of the molecular hydrogen emission is also comparable to the size scale of molecular gas in more nearby spirals. These facts, combined with the known presence of tidal tails and a double nucleus support a picture in which two spiral galaxies have collided, their bulge populations are now seen overlapped, if not merged, and their molecular disks have impacted in a strongly dissipative manner. The strongest remaining evidence for widespread star formation is the depth of the CO bands in the near-infrared spectrum. These bands suggest that a young population of supergiants dominates the near-infrared continuum from this object, though an extremely late-type and perhaps metal-rich giant population could be the cause. There is some evidence that the H_2_ emission is spatially more extended than the continuum, however, so that the mechanism for H_2_ line emission may be uncoupled from the region in which stars have been formed. Publication: The Astrophysical Journal Pub Date: June 1988 DOI: 10.1086/166410 Bibcode: 1988ApJ...329..641L Keywords: Galactic Structure; H Lines; Infrared Spectra; Interstellar Gas; K Lines; Luminous Intensity; Active Galactic Nuclei; Emission Spectra; Interstellar Extinction; Line Spectra; Star Formation; Astrophysics; GALAXIES: INDIVIDUAL NGC NUMBER: NGC 6240; GALAXIES: INTERSTELLAR MATTER; GALAXIES: STELLAR CONTENT; INFRARED: SPECTRA full text sources ADS | data products SIMBAD (2) NED (2)

IR-induced UV-visible fluorescence in matrix-isolated CO

UV-visible fluorescence from solid argon containing 1% of 13C 18O is observed upon irradiation by a color-center laser whose frequency is coincident with the first overtone absorption band of CO. This emission consists of an intense complex system between 650 and 800 nm and a weaker single progression extending from 320 to 640 nm. Both systems are assigned to electronic transitions of molecular oxygen. Infrared emission spectra indicate that high-lying vibrational levels of CO (up to ν = 30) are populated by anharmonic V-V pumping. Subsequent emission from C 3Δ and b 1Σ g + states of O 2 suggests that vibrational-to-electronic energy transfer occurs. Vibrationally unrelaxed emission from the singlet state of oxygen indicates that the vibrational relaxation of O 2(b 1Σ g +) in Ar is slow.

Intensity, transition moment, and bandshapes for the second overtone of compressed CO

Infrared spectra of the CO second overtone absorption band have been studied for pressures up to 156 bar. The absolute intensity, obtained from direct measurements of the total band, is found to be (1.27 ± 0.04) × 10 -2 cm -2 Am -1 at 298 K. Using the vibrational moments for the ground state and the transitions 0–1 to 0–4, we have evaluated the coefficients M 0 to M 4 of the quartic dipole moment function for CO and the coefficients of the vibration-rotation interaction functions. The normalized 0–3 band contours of compressed CO were first generated by summing the pressure-broadened rotational lines with Lorentz profiles. A discrepancy appears between calculated and observed bandshapes and increases with density. An empirical model, which involves the sum of CO self-broadened lines with profile described as the product of a Lorentz function by a fitted exponential function, gives reasonable agreement with the experiments. The interference effects resulting from overlapping lines have been estimated within the impact approximation.

Bandshapes and dipole correlation functions for the first overtone of CO compressed by N 2

Infrared spectra of the first overtone absorption band of CO compressed by N 2 at pressures up to nearly 1000 bar have been studied at room temperature. The integrated intensities, as well as the wavenumbers of the maximum absorption for the P- and R-branches and of the minimum absorption between these branches, have been measured as functions of the N 2 density. The dipole moment autocorrelation function has been used to assess the Gordon J-diffusion model and the semi-classical M-model. The normalized band contours are calculated by summing the absorption coefficients for the pressure-broadened rotational lines with a modified Lorentz shape derived from an analysis of individual lines. This model gives reasonable agreement with experiments for densities below 200 Am. The discrepancy between calculated and experimental bandshapes, which increases with density, may be caused by strong overlapping effects and a probable nonlinear variation of the linewidths with density. Consideration of interferences between adjacent rotational lines in the frame of the impact approximation would not be sufficient to provide satisfactory agreement with the experimentally observed band contours.

Intensity, bandshapes and dipole correlation functions for the first overtone of compressed CO

Infrared spectra of the CO first overtone absorption band have been studied at room temperature for pressures up to 104.5 bar. The integrated intensities are found to be proportional to the gas density. The dipole moment autocorrelation function is used to assess a collisional model derived from the impact approximation and the Gordon M- and J-diffusion models developed classically, as well as the semi-classical M-diffusion model. The semi-classical M-model, which is better than the classical models, reproduces the experimental correlation functions well only for densities up to about 40 Am. From an analysis of the individual lines at low pressures, we conclude that their profiles are the product of a Lorentz function and of an empirical exponential function. The normalized band contours are calculated by summing the pressure-broadened rotational lines, assuming for these lines successively a Lorentz shape and two modified Lorentz shapes derived from the low-pressure line analysis. In the first case, a discrepancy between theoretical and experimental bandshapes become noticeable from about 20 Am and increases with density. The results are greatly improved by using two other models, one of which gives reasonable agreement with the experiments at all pressures. At high pressures, interference effects between the strongly overlapping lines are probably not negligible.

Determination of the hydration numbers of molecules and ions from the overtone bands in the IR spectrum of water

1. Measurement has been made of the variation of the optical densities of the water overtone absorption bands with the concentration of water in aqueous solutions of acids and salts. 2. Deviations from Beer's law have been used to calculate values of nυ defined as the ratio of the difference of the analytical and measured concentrations of water to the concentrations of the dissolved compound. 3. Analysis of our own data and those of the literature indicated that the nυ value is often identical with the hydration number of hydrogen or hydroxide ions in strong aqueous solutions of acids and bases. 4. In general, there is no correlation between nυ values and hydration numbers in aqueous salt solutions.

Temperature Dependence of the Fundamental and Overtone Absorption Bands of Phosphorus-Doped GaAs

Temperature Dependence of the Fundamental and Overtone Absorption Bands of Phosphorus-Doped GaAs

Infrared Combination Mode Absorption in Lithium-Boron-Doped Silicon

Infrared absorption bands due to double-quantum transitions of local lattice-mode vibrations in boron-lithium-doped silicon have been observed. The transitions are found near twice the frequency of all local modes and at the sum frequency of the two strongest local-mode vibrations, which are those associated with boron-lithium pairs. The relative strengths of the pair modes, the displacement of the modes from the mode due to isolated substitutional boron, and the relative strengths of the overtone absorption bands are consistent with the assumption of a predominantly Coulomb interaction between the boron and lithium ions. Five additional absorption bands, with frequency depending upon boron isotope, are found at frequencies not corresponding to sums of local-mode frequencies. Four of these bands occur at sum frequencies of the two strongest local-mode frequencies and of silicon critical-point phonon frequencies. The dependence of the frequency of all absorption peaks on lithium and boron isotopes is used to assist in the assignment of the absorption bands.

Hydrogen Bonding in Organic Compounds. VIII. Aromatic Primary Amines with ortho-Carbonyl Groups

The NH stretching frequencies of the amine group in a number of aromatic primary amines with o-carbonyl groups have been studied as the fundamental and first overtone absorption bands, both before and after deuteration. Several correlations are established between functions of the vibration frequencies which seem to be related to the strengths of the hydrogen bonds that have been formed. These correlations, established for carbonyl as the acceptor, extend to some other classes of hydrogen bond acceptor. When bilateral hydrogen bonds are formed to two o-carbonyl groups the NH2 stretching frequencies do not conform to the equation of Bellamy and Williams. Further evidence in favour of the interpretation of the spectrum of 1-aminoanthraquinone given by Hambly and Bonnyman is offered. The preparation of 5-chloro-2-t-butylaniline is described and some further details of the spectra of anilines with tertiary butyl substituents are given.