Infrared Absorption Characteristics Research Articles

Chalcogenide 광섬유를 이용한 호흡측정 센서 개발을 위한 기초 연구

In this study, we have fabricated an infrared optical fiber based sensor which can monitor the respiration of a patient. The design of a chalcogenide optical fiber based sensor is suitable for insertion into a high electro-magnetic field environment because the sensor consists of low cost and compact mid-infrared components such as an infrared light source, a chalcogenide optical fiber and a thermopile sensor. A fiber-optic respiration sensor is capable of detecting carbon dioxide (<TEX>$CO_{2}$</TEX>) in exhalation of a patient using the infrared absorption characteristics of carbon gases. The modulated infrared radiation due to the presence of carbon dioxide is guided to the thermopile sensor via a chalcogenide receiving fiber. It is expected that a mid-infrared fiber-optic respiration sensor which can be developed based on the results of this study would be highly suitable for respiration measurements of a patient during the procedure of an MRI.

Infrared absorption characteristics of polycrystalline iridium-silicide thin films

The iridium-silicide (IrSi) polycrystalline nanometer thin films have been deposited on p-Si(100) substrates by a pulsed laser deposition at a room temperature and followed by in situ annealing at 300, 500, and 800 °C, respectively. The Schottky barrier heights (SBHs) of 0.185, 0.178 and 0.177 eV have been determined by I– V measurements. The SBHs decrease with an increase of annealing temperature due to the nanometer size effect of the IrSi polycrystalline. The measured maximum responsivity of the sample is up to 10 mA/W.

Absorption and emission of ErNbO4 powder

Abstract Visible and near infrared absorption and emission (488 nm excitation) characteristics of ErNbO4 powder, which were prepared by calcining the Er2O3 (50 mol%) and Nb2O5 (50 mol%) powder mixture at 1100 and 1600 °C for different durations, have been investigated at room temperature. The absorption and emission characteristics of these calcined ErNbO4 powder were summarized and discussed in comparison with those of Er2O3. Weak emission of Er2O3 relative to the calcined ErNbO4 is mainly conducted with absorption difference at the excitation wavelength 488 nm. The obvious spectral changes from Er2O3 to calcined ErNbO4 samples are related to an elevated-temperature-assisted phase transformation according to the solid-state chemical reaction equation: Er2O3 + Nb2O5 ⇌ 2ErNbO4, which results in the changes of the ion environment of Er3+ and hence changes of the Stark levels of Er3+. The further spectral change as the strengthened calcination results from the improvement of ErNbO4 purity in the calcined mixture. The borders between two green transitions and between two near infrared transitions in the emission spectra of both calcined samples and Er2O3 were tentatively identified by referencing earlier reported emission spectra of the precipitated Z-cut VTE Er(2.0 mol%):LiNbO3 crystal and the match relation between absorption and emission spectra of the ErNbO4 powder. A comparison was performed on the spectra of calcined ErNbO4 powder and those of VTE Er(2.0 mol%):LiNbO3 crystals. The results allow to preliminarily deem the contribution of ErNbO4 precipitates, generated inside these crystals by the VTE procedure, to the spectra of these crystals.

Fingerprint IR spectroscopy to probe amino acid conformations in the gas phase.

We report the infrared (IR) absorption spectra of different conformational isomers of gas phase amino acid molecules in the molecular fingerprint region of 330-1500 cm(-1). The IR absorption spectra for three conformers of the amino acid tryptophan show absorption bands that uniquely identify the conformational structure of the molecule and that are well matched by density functional theory calculations. The present observations hold great promise for future identification of conformational folding of larger molecules by means of their IR absorption characteristics.

1,8‐Naphthalimides as Blue Emitting Fluorophores for Polymer Materials

AbstractThe copolymerization of 1,8‐naphthalimide derivatives (as fluorophore) with acrylonitrile has been investigated. The photophysical characteristics of monomeric and polymeric fluorophores in N,N‐dimethylformamide solution have been determined and discussed. During copolymerization, no changes in the chromophoric systems of the fluorophore occur. The influence of the studied monomeric 1,8‐naphthalimide fluorophores upon the structurally bleached polyacrylonitrile has been determined. Infrared absorption characteristics of the polymerizable 4‐alkoxy‐ and 4‐allyloxy‐N‐substituted‐1,8‐naphthalimides have been measured and discussed. The effect of the substituents upon the vibration frequencies of the carbonyl and allylic groups has been established.Blue fluorescent polyacrylonitrile copolymers with 1,8‐naphthalimides side‐group.magnified imageBlue fluorescent polyacrylonitrile copolymers with 1,8‐naphthalimides side‐group.

The Temperature Dependence of the Infrared Absorption and Raman Spectra Due to Boron in Diamond

Raman scattering and infrared absorption characteristics of B-doped CVD diamond have been studied as a function of the temperature. First order Raman measurements show that the energy and the width of the Raman line depend on the acceptor concentration and, in particular for N A > 10 2 0 cm - 3 , the peak becomes asymmetric. This is due to a Fano resonance interaction, already reported in literature for samples with similar boron concentrations. The dependence of the Raman energy on temperature is reported; it is shown that the shift to lower energy due to anharmonic processes can be described by the Klemens model. Raman data have been compared to infrared absorption results previously obtained. The Fano resonance is also observed in infrared spectra at 1332 cm - 1 for samples with lower boron concentrations. The comparison of these features shows that two different processes take place.

Infrared spectrometric study of acid-degradable glasses.

The composition of glasses used in glass-ionomer cements affects their leaching behavior and hence the properties of the cement. The aim of this study was to correlate the composition and leaching behavior of these glasses with their infrared absorption characteristics. The wavenumber of the absorption band of the Si-O asymmetric stretching vibration shifts to a higher value with decreasing content of mono- and bivalent cations in the glass. This effect can be ascribed to the influence of these extraneous ions on the glass network order and connectivity. Preferential leaching of these ions induces an increase of asymmetric stretching vibration and a general modification of the band profile. The results can be correlated with the x-ray diffraction characteristics of the glass.

Reduction of dark current in an n-type In 0.3Ga 0.7As/GaAs quantum well infrared photodetector by using a camel diode structure

Long wavelength infrared absorption characteristics of an In 0.3Ga 0.7As/GaAs quantum well infrared photodetector (QWIP) employing an n-i-p-i-n camel diode structure were compared with those of a conventional n-QWIP. The QWIPs showed a photocurrent response peak at the wavelength of approximately 10 μm due to electronic intersubband transitions in quantum wells. The QWIP employing the camel diode structure showed a reduced dark current, an increased responsivity, and thus an improved detectivity compared with those of the conventional n-QWIP due to the presence of the n-i-p-i-n camel barrier. The results indicated the potential of the QWIP employing an n-i-p-i-n camel diode structure for use in infrared detectors operating at elevated operating temperature.

Are Phragmites-dominated wetlands a net source or net sink of greenhouse gases?

Phragmites australis wetlands act as a sink for greenhouse gases by photosynthetic assimilation of carbon dioxide (CO 2) from the atmosphere and sequestration of the organic matter produced in the wetland soil. The wetlands also act as a source for greenhouse gases by emission of sediment-produced methane (CH 4) to the atmosphere. In P. australis wetlands, the dominant mechanism of CH 4 release to the atmosphere is internal gas transport in the plants, primarily by pressurized convective gas flow. The time periods of carbon fixation and CH 4 release therefore vary seasonally and diurnally. The balance between net CO 2-assimilation and CH 4 emission determines if a wetland can be regarded as a net sink or a net source of greenhouse gases, and hence, the function of the wetland in relation to global climate change. On an annual basis up to 15% of the net carbon fixed by the wetlands may be released to the atmosphere as CH 4. Because of the different infrared absorption characteristics and atmospheric longevity of CH 4 and CO 2, the warming effect of CH 4 in the atmosphere is about 21 times higher on a mass basis than CO 2 over a 100-year timescale. Thus, the immediate carbon balance, coupled with the different physical characteristics of the two gases, would suggest that although some wetlands function as a net sink for CO 2, the wetlands still increase the greenhouse effect because of their release of CH 4. However, the short adjustment time for CH 4 in the atmosphere means that, over a longer time scale, the radiative forcing of CH 4 is less relative to CO 2 and the wetlands effectively become a sink for greenhouse gases. Wetlands may therefore be regarded as a source for greenhouse gases and so increase radiative forcing if evaluated on a short time scale (decades), but as a sink for greenhouse gases and thus attenuating radiative forcing if evaluated over longer time scales (>100 years).

IR absorption characteristics of an IR moisture sensor and mechanism of water transfer in fluidized bed granulation

Monitoring of moisture content by an infrared (IR) moisture sensor during fluidized bed granulation is a necessary way to control granule growth; however, this method requires prior investigation of IR absorption characteristics indicating the relationship between granule moisture content and IR absorption. In this contribution. for a better understanding of this IR absorption characteristics, fluidized bed granulation and drying were conducted at various powder samples and operating conditions with monitoring of moisture content by an IR moisture sensor. The effects of powder properties such as water absorbing potential and diameter on the IR absorption characteristics were investigated experimentally. Based on the results obtained, the water transfer mechanism among particles was analyzed, and factors which determined the IR absorption characteristic during fluidized bed granulation and drying were discussed.

Optical studies of chemical doping achieved by ion implantation in poly(p‐phenylene vinylene)

Abstract Measurements of the optical properties of thin films of poly(p‐phenylene vinylene) (PPV) implanted with caesium, xenon and iodine at a low energy (30 keV) are reported. Optical absorption shows evidence for graphitization at high fluences, independent of the ion type. In contrast, for samples implanted with caesium and with iodine, the optical absorption due to charge accumulation in the PPV layer, formed within a field‐effect device, shows infrared absorption characteristics of a chemically doped polymer which are associated with charged bipolarons. Photoluminescence is quenched as a result of ion implantation. We model this in terms of exciton migration over a characteristic distance of 10–15 nm to quenching centres introduced by the implantation.

Synthesis and infrared absorption characteristics of boron-doped semiconducting diamond thin films

Boron-doped semiconducting diamond films were synthesized by the thermal filament CVD technique, using acetone as a carbon source and trioxide (B 2O 3) as an impurity source. The infrared absorption spectra of undoped and boron-doped diamond films are reported. The experimental results show that the absorption peaks at 0.308 and 0.341 eV are the first and second excited state respectively, arising from a common ground in B atoms in diamond films. These results have confirmed that the B atoms in diamond films are in substitutional position.

A phase map for sputter deposited niobium oxides

A Nb target was sputtered in radio frequency (rf) Ar/O2 and Ne/O2 discharges, and films were grown on unheated fused silica, 〈111〉-cut Si, and carbon ribbon. The transition from Nb metal to niobia film growth was studied as a function of three independent process parameters: cathode voltage, gas O2 content, and rare gas type. On the basis of x-ray diffraction results, resistivity, optical transmission, refractive index, Nb:O ratio, and infrared absorption characteristics, the following phases were identified in the films: bcc Nb, NbO, NbO2, x-niobia, amorphous niobia, microcrystalline niobia, and crystalline niobia (where niobia=Nb2O5−x with 0≤x≤0.2). In situ optical spectrometry of the discharge was used to monitor the emission intensity I(λ) of four radiative electronic transitions of the neutral excited Nb atom to ground state (λ=5344, 5079, 4101, and 4059 Å). Changes in I(λ) and the growth rate was used to (1) determine the set of process parameters at which target surface oxidation occurred, and (2) estimate the fractional flux of atomic Nb and Nb bonded to O in an unspecified molecular form (Nb-oxide) incident on the substrate. Film structure was found to depend to some extent upon this fractional flux. A phase map was constructed in which film structure and the Nb and Nb-oxide fractional flux were graphed onto process parameter space, demonstrating the equivalent effect of different sets of process parameters.

Optical properties of finely structured metal-insulator superlattice particulates

We investigate the optical properties of new ‘‘superlattice particles’’ that can be made of precisely controlled metal-insulator layers fabricated by sputtering or evaporation techniques. We found that there are two limits to the reflectivity behavior corresponding to wide and narrow particles. In the narrow-particle limit, a series of sharply defined absorption peaks at frequencies controlled by the width is observed. In the wide-particle limit, most of the light incident on the particles will be absorbed. Materials of this type possess desirable infrared absorption characteristics and can be used for new polarization sensitive infrared absorbers and detectors.

Infrared absorption of?-SiC particles prepared by chemical vapour deposition

Infrared absorption characteristics ofβ-SiC particles prepared by chemical vapour deposition were studied. These particles were either solid or had a silicon core and/or were hollow. The solid particles exhibited a single absorption peak between the transverse optical frequency (ωTO = 794 cm−1) and the longitudinal optical frequency (ωLO = 976 cm−1) ofβ-SiC. This absorption peak shifted to a lower frequency with increasing lattice parameter ofβ-SiC and increasing free silicon content. The particles containing a silicon core and/or were hollow exhibited double absorption peaks close to ωTO and ωLO. The peak at the LO side shifted to a lower frequency and that at the TO side to a higher frequency with decreasing silicon core size and increasing hollow size. Using the calculations based on the effective medium theory assuming surface phonon mode, the relationship between the infrared absorption characteristics and microstructures of theβ-SiC particles are explained.

INFRARED RADIATION OF SF6AND ITS APPLICATION TO GAS-FILLED DOUBLE-PANE WINDOWS

Interest in using sulfur hexafluoride (SF6 as a gas-fill in multipane windows has raised questions concerning the calculation of heat transfer rates through such windows. The infrared absorption characteristics of this gas make the heat transfer analysis much more complicated. In order to account for the absorption effect, we measured the spectral absorptivity of several infrared-active bands of sulfur hexafluoride at low resolution and a temperature of 298 K. We correlated the spectral absorption data with the Edwards exponential wide-band model and with the Elsasser narrow-band model, and incorporated the wide-band model into a one-dimensional, finite-element heat transfer model. The finite-element heat transfer model considered combined conduction and radiation effects in a double-pane window, and was used to evaluate the overall heat transfer coefficients of double-pane windows filled with SF6; CO2, or air. The numerical results show good agreement with the experimental results

Infrared absorption characteristics and electrical conduction of methyl methacrylate‐lithium acrylate copolymers

AbstractSemiconducting copolymer samples were prepared by bulk copolymerization of methyl methacrylate with lithium acrylate using benzoyl peroxide as initiator. The pattern of the chemical reaction is discussed. The obtained samples were found to be random copolymers. Infrared absorption spectra were measured and analysed according to the copolymer structures. The data of electrical conductivity and the effect of gamma radiation on the electrical conductivity of the copolymer samples are discussed.

The infrared absorption characteristics of poly(methyl methacrylate) doped with luminescent materials

AbstractThe infrared spectra of poly(methyl methacrylate) samples doped with different luminescent materials show no drastic changes in the position and intensity of the absorption bands, except in case of β‐naphthol. From this it is supposed that there is no interaction between the dopant and PMMA with most of the investigated materials, while with β‐naphthol hydrogen bonding between adjacent molecules in the polymer matrix is observed.

Infrared absorption characteristics of hydroxyl groups in coal tars

Tar evolution was observed over a temperature range of 150–600 °C for four coals: Pittsburgh bituminous, Illinois No. 6, Rawhide subbituminous, and Texas lignite. Isolation of the evolved tars in a nitrogen matrix at 15 °K produced better resolved infrared spectra than those in a coal matrix, thus enhancing structural characterization of the tar molecules. Two distinct hydroxyl functional groups in the tar molecules free of hydrogen bonding were identified for the first time without interference from H 2O absorptions. These absorptions at 3626.5 and 3580.9 cm −1 have been assigned to phenolic hydroxyls. It is suggested that carboxylic and aliphatic hydroxyl groups do not survive the vaporization process. Tars from Illinois No. 6 were found to contain the largest amount of phenolic hydroxyl ; Pittsburgh No. 8 tar contains approximately half of that for Illinois No. 6 while Rawhide and Texas lignite contain much less phenolic than either of the other coals.

An ab-initio study of the vibrational spectra of the ion hydrates H +(H 2O) 2 and H +(H 2O) 3

The vibrational spectra of the ions H 5O 2 + and H 7O 3 + have been calculated using ab-initio molecular-orbital theory in the harmonic approximation. The calculations indicate that the structures of the two ions are best represented as H +(H 2O) 2 and H 3O +(H 2O) 2, respectively. The vibrational frequencies of the two ion hydrates are analysed in terms of their respective structures and compared with the previously reported vibrational spectrum of the neutral water dimer. The general infrared absorption characteristics of the two ion hydrate clusters and those of the neutral (H 2O) 2 cluster are discussed.