From Far-infrared Research Articles

Assessment of Optical and Phonon Characteristics in MOCVD-Grown (AlxGa1-x)0.5In0.5P/n+-GaAs Epifilms.

Quaternary (AlxGa1-x)yIn1-yP alloys grown on GaAs substrates have recently gained considerable interest in photonics for improving visible light-emitting diodes, laser diodes, and photodetectors. With two degrees of freedom (x, y) and keeping growth on a lattice-matched GaAs substrate, the (AlxGa1-x)0.5In0.5P alloys are used for tuning structural, phonon, and optical characteristics in different energy regions from far-infrared (FIR) → near-infrared (NIR) → ultraviolet (UV). Despite the successful growth of (AlxGa1-x)0.5In0.5P/n+-GaAs epilayers, limited optical, phonon, and structural characteristics exist. Here, we report our results of carefully examined optical and vibrational properties on highly disordered alloys using temperature-dependent photoluminescence (TD-PL), Raman scattering spectroscopy (RSS), and Fourier-transform infrared reflectivity (FTIR). Macroscopic models were meticulously employed to analyze the TD-PL, RSS, and FTIR data of the (Al0.24Ga0.76)0.5In0.5P/n+-GaAs epilayers to comprehend the energy-dependent characteristics. The Raman scattering and FTIR results of phonons helped analyze the reflectivity spectra in the FIR region. Optical constants were carefully integrated in the transfer matrix method for evaluating the reflectivity R(E) and transmission T(E) spectra in the NIR → UV regions, validating the TD-PL measurements of bandgap energies (EgPL).

Severe perturbation and observation of forbidden transitions in asymmetrically deuterated methanol (CHD2OH) and atlas of very accurate torsional rotational spectrum obtained using Synchrotron radiation

High-resolution spectral studies have been continued for the doubly deuterated methanol species (CHD2OH) in the entire region from far infrared (FIR) to Infrared (IR). The spectrum has been obtained using a conventional Fourier transform spectrometer and the state-of-the-art Synchrotron radiation-based spectrometer with unprecedented resolution and very high signal-to-noise (S/N). During the investigation severe perturbation was encountered. The perturbation has been characterized as due to first and second-order Coriolis interaction. The interaction affected a wide range of states and caused the spectral study quite challenging. The perturbation caused a variety of mixing of states producing hybrid states. This hybridization resulted in producing a large number of transitions which should not be allowed by the dipole selection rules via the “intensity borrowing effect”. It was possible to identify a large number of such forbidden transitions that gain sufficient strength through the “Intensity borrowing” effect. The transitions connecting to these perturbed states have been analyzed using standard Coriolis interaction formulae. The possibility of “Fermi” interaction has been excluded as the interaction is highly dependent on the rotational quantum number J. In general, this kind of transition should be excluded from global analysis and should be treated in isolation. It is pertinent to note that some previously published works studied these states using un-substantiated assignments being perhaps unaware of the perturbation. Corrections have been suggested for the analysis and understanding of the properties of the energy levels which have subtle differences with the energy levels of normal asymmetric molecules. In all, available microwave (MW) millimeter wave (MMW) far infrared (FIR), and infrared (IR) assignments have been put together to prepare the most accurate and and complete atlas of about 12,000 spectral lines. This atlas (Appendix A) should be considered a work-in-progress supplement to this paper and supersedes all other lists known to date on this species can be had from one of us (IM) or via Researchgate.

Discovery of Four Apparently Cold Dusty Galaxies at z = 3.62–5.85 in the COSMOS Field: Direct Evidence of Cosmic Microwave Background Impact on High-redshift Galaxy Observables

Abstract We report Atacama Large Millimeter Array (ALMA) observations of four high-redshift dusty star-forming galaxy candidates selected from far-infrared (FIR)/submillimeter observations in the COSMOS field. We securely detect all galaxies in the continuum and spectroscopically confirm them at z = 3.62–5.85 using ALMA 3 mm line scans, detecting multiple CO and/or [C i] transitions. This includes the most distant dusty galaxy currently known in the COSMOS field, ID85001929 at z = 5.847. These redshifts are lower than we had expected, as these galaxies have substantially colder dust temperatures (i.e., their spectral energy distributions peak at longer rest-frame wavelengths) than most literature sources at z > 4. The observed cold dust temperatures are best understood as evidence for optically thick dust continuum in the FIR, rather than the result of low star formation efficiency with rapid metal enrichment. We provide direct evidence that, given their cold spectral energy distributions, cosmic microwave background (CMB) plays a significant role in biasing their observed Rayleigh–Jeans (RJ) slopes to unlikely steep values and, possibly, reducing their CO fluxes by a factor of two. We recover standard RJ slopes when the CMB contribution is taken into account. High-resolution ALMA imaging shows compact morphology and evidence for mergers. This work reveals a population of cold dusty star-forming galaxies that were underrepresented in current surveys and are even colder than typical main-sequence galaxies at the same redshift. High FIR dust optical depth might be a widespread feature of compact starbursts at any redshift.

New synthesis models of consistent extragalactic background light over cosmic time

We present new synthesis models of the extragalactic background light (EBL) from far infra-red (FIR) to TeV gamma-rays, with an emphasis on the extreme ultraviolet (UV) background which is responsible for the observed ionization and thermal state of the intergalactic medium across the cosmic time. Our models use updated values of the star formation rate density and dust attenuation in galaxies, QSO emissivity, and the distribution of H I gas in the IGM. Two of the most uncertain parameters in these models, the escape fraction of H I ionizing photons from galaxies and the spectral energy distribution (SED) of QSOs, are determined to be consistent with the latest measurements of H I and He II photoionization rates, the He II Lyman-alpha effective optical depths, various constraints on H I and He II reionization history and many measurements of the local EBL from soft X-rays till gamma-rays. We calculate the EBL from FIR to TeV gamma-rays by using FIR emissivities from our previous work and constructing an average SED of high-energy emitting QSOs, i.e, type-2 QSOs and blazars. For public use, we also provide the EBL models obtained using different QSO SEDs at extreme-UV energies over a wide range of redshifts. These can be used to quantify uncertainties in the parameters derived from photoionization models and numerical simulations originating from the allowed variations in the UV background radiation.

Pixelless image deformation characteristics due to optoelectronic integration between quantum well infrared phototransistor and light emitting diode

This manuscript focused on image processing due to optoelectronic integration instruments between quantum well infrared phototransistor and light emitting diode (QWIPT-LED). Thus, characteristics analysis of pixelless images deformation due to QWIPT-LED optoelectronic integration instruments are the aim of this manuscript. Pixelless images reabsorption and reemission challenges during radiative conversion from far infrared (FIR) to near infrared (NIR) are addressed. Overcoming the photons recycling process that deteriorate the output image is the main objective. Therefore, curves for the image characteristics are presented with special emphasis on the carrier’s concentration within the QWIPT-LED optoelectronic devices. These characteristics include contrast transfer function and image resolution. Besides providing a complete analysis of image characteristics, this paper extends the analysis to the image conversion efficiency that figure-of-merit characteristic of QWIP-LED. Additionally, the performance of the underlined characteristics is conducted through closed form expressions. The spatial distribution of the electrons concentration that injected from quantum well infrared phototransistor (QWIPT) into light emitting diode (LED) active layer is considered. Also, the effects of image uniformity and nonuniformity on the image contrast and image resolution are presented. Also, the investigation and description of carrier’s movement within optoelectronic QWIPT-LED is perceived. Moreover, optimization of this optoelectronic integrated device is of concern. The obtained result confirms that contrast transfer function of the image depends on the lithography process during integration between QWIPT and LED as well as structural parameters. These parameters represent the LED thickness of the device portion, radiative recombination, non-radiative recombination, number of quantum well (QW) and period length of the QW. As a final conclusion, the reabsorption process can be minimized by optimal design of the structure parameters with number of QW of 14, thicknesses of QWIPT 120 μm and life time ratio of 0.999. These obtained results confirm the potential applicability of the proposed work of QWIPT-LED pixelless image instrument for image conversion under various parameters conditions. Hence, better performance of QWIPT-LED pixelless image instrument can be achieved.

Heat Effects from Far-Infrared Source towards Antioxidant Activity in <i>Aquilaria</i> <i>subintegra</i> Leaves

Aquilaria tree is known for its ability of producing high quality resin called agarwood or gaharu oil. The leaves of this tree were under utilized and it is also claimed to be useful for treating a certain diseases. This study was aimed to identify the present of antioxidant activities in Aquilariasubintegra leaves. In the meantime, the effect of drying temperature from far-infrared (FIR) sources on antioxidant activity of the plant leaves was studied. Leaves were dried at different temperatures (40 °C, 50 °C, 60 °C) by using a (FIR) dryer. DPPH method was used to identify the scavenging activity (IC50) of the methanolic leaves extracts. The result showed that methanol extract of the sample dried at 50 °C exhibited the highest antioxidant activity (IC50 of 619.89μg/ml). In the range of temperature studied, 50 °C is proposed to be an appropriate drying temperature when using FIR as the source of heating element. In conclusion, FIR helps in lowering the drying temperature of Aquilariasubintegra leaves that retain significant amount of antioxidant activities which could be beneficial for treating certain diseases as claimed by others.

Constraining spatial extent and temperature of dust around galaxies from far-infrared image stacking analysis

We propose a novel method to constrain the spatial extent of dust around galaxies through the measurement of dust temperature. Our method combines the dust emission of galaxies from far-infrared (FIR) image stacking analysis and the quasar reddening due to the dust absorption around galaxies. As a specific application of our method, we use the stacked FIR emission profiles of SDSS photometric galaxies over the IRAS 100$\mu$m map, and the recent measurement of the SDSS galaxy-quasar cross-correlation. If we adopt a single-temperature dust model, the resulting temperature is around 18K, which is consistent with a typical dust temperature for a central part of galaxies. If we assume an additional dust component with much lower temperature, the current data imply the temperature of the galactic dust needs to be higher, 20K to 30K. Since the model of the density and temperature distribution of dust adopted in the current paper is very simple, we cannot draw any strong conclusion at this point. Nevertheless our novel method with the elaborated theoretical model and multi-band measurement of dust will offer an interesting constraint on the statistical nature of galactic dust.

Properties of active galactic star-forming regions probed by imaging spectroscopy with the Fourier transform spectrometer (FTS) onboard AKARI

We investigate the structure of the interstellar medium (ISM) and identify the location of possible embedded excitation sources from far-infrared (FIR) line and mid-infrared continuum emission maps. We carried out imaging spectroscopic observations of four giant Galactic star-forming regions with the Fourier Transform Spectrometer (FTS) onboard AKARI. We obtained [OIII] 88 micron and [CII] 158 micron line intensity maps of all the regions: G3.270-0.101, G333.6-0.2, NGC3603, and M17. For G3.270-0.101, we obtained high-spatial-resolution [OIII] 88 micron line-emission maps and a FIR continuum map for the first time, which imply that [OIII] 88 micron emission identifies the excitation sources more clearly than the radio continuum emission. In G333.6-0.2, we found a local [OIII] 88 micron emission peak, which is indicative of an excitation source. This is supported by the 18 micron continuum emission, which is considered to trace the hot dust distribution. For all regions, the [CII] 158 micron emission is distributed widely as suggested by previous observations of star-forming regions. We conclude that [OIII] 88 micron emission traces the excitation sources more accurately than the radio continuum emission, especially where there is a high density and/or column density gradient. The FIR spectroscopy provides a promising means of understanding the nature of star-forming regions.

Terahertz Response of a Microfabricated Rod–Split-Ring-Resonator Electromagnetic Metamaterial

The first electromagnetic metamaterials (EM3) produced by microfabrication are reported. They are based on the rod-split-ring-resonator design as proposed by Pendry et al. [IEEE Trans. Microwave Theory Tech. 47, 2075 (1999)] and experimentally confirmed by Smith et al. [Phys. Rev. Lett. 84, 4184 (2000)] in the GHz frequency range. Numerical simulation and experimental results from far infrared (FIR) transmission spectroscopy support the conclusion that the microfabricated composite material is EM3 in the range 1-2.7 THz. This extends the frequency range in which EM3 are available by about 3 orders of magnitude well into the FIR, thereby widely opening up opportunities to verify the unusual physical implications on electromagnetic theory as well as to build novel electromagnetic and optical devices.

Toward a Resolution of the Discrepancy between Different Estimators of Star Formation Rate

Different wavelength regimes and methods for estimating the space density of the star formation rate (SFR) result in discrepant values. While it is recognized that ultraviolet (UV) and Hα emission-line data must be corrected for the effects of extinction, the magnitude of the required correction is uncertain. Even when these corrections are made there remains a significant discrepancy between SFRs derived from UV and Hα measurements compared with those derived from far-infrared (FIR) and radio luminosities. Since the FIR-radio–derived SFRs are not affected by extinction and simple corrections to reconcile the UV and Hα measurement with these do not fully account for the discrepancies, a more sophisticated correction may be required. Recent results suggest that at least part of the solution may be a form of extinction that increases with increasing SFR (or luminosity, given the common assumption that SFR is proportional to luminosity). We present an analysis of the effects of a dust reddening dependent on star formation rate applied to estimators of SFR. We show (1) that the discrepancies between Hα and FIR-radio SFR estimates may be explained by such an effect and we present an iterative method for applying the correction and (2) that UV-based estimates of SFR are harder to reconcile with FIR-radio estimates using this method, although the extent of the remaining discrepancy is less than for a non-SFR–dependent correction. Particularly at high redshift, our understanding of extinction at UV wavelengths may require a still more complex explanation.

Hard X-Ray Emission from Massive Star Clusters in a Giant Molecular Cloud NGC 6334

Abstract We report on detection with the ASCA satellite of hard X-rays from far infrared (FIR) star clusters in the giant molecular cloud (GMC) cores of the NGC 6334 star-forming region. Five FIR cores are visible in the hard X-ray band (E > 2 keV), while in the soft X-ray band (E < 2 keV) the emission is absorbed, except for one core. The observed spectra can be fitted with thermal emission from a hot plasma, whose temperature of ∼ 9 keV is significantly higher than those reported of low-mass Class I pre-main-sequence stars (PMSs) ( ∼ 3 keV) in nearby dark clouds and those of OB-type main-sequence stars (∼ 1 keV). The X-ray luminosity of each core is typically 1033 erg s−1 or 103 times that of typical low-mass PMSs. The observed hard X-rays may be emitted from young massive stars and loss-mass/intermediate-mass PMSs in the FIR cores. The observed hard X-ray flux can ionize the inner part (r ∼ 0.3 pc) of the GMC cores at a rate comparable to that by cosmic-ray particles. If the LX/M ratio of ∼ 10−5L⊙/M⊙ observed in NGC 6334 is typical among GMCs, the X-ray flux from all GMCs in the Galaxy ( ∼ 109L⊙) can account for about 20% of the diffuse galactic ridge hard X-ray emission.

Detection and Mixing Properties of an InSb Metal-Semiconductor Point Contact Diode

We present preliminary data on the performance of a new fast photodetector based on a W–InSb metal-insulator-semiconductor point contact diode operating at room temperature and with no bias voltage. The device can work either as a video detector or as harmonic mixer for radiation from far–infrared (FIR) to visible. In the FIR region, for wavelengths from 200 to 400 μm, the W–InSb point contact diode showed a sensitivity comparable to that of Golay cells. In the visible region the device showed a video and heterodyne detection responsivity much higher with respect to standard M.I.M. point contact diodes. Owing to its ruggedness, low cost and wide band of operation, the W–InSb point contact diode may be very attractive as a general purpose optical sensor.

A far-infrared H-R diagram of young stellar objects

The observed spectral energy distributions from far-infrared (FIR) to millimeter wavelengths of young stellar objects (YSOs) fit a modified blackbody radiation with a peak around 100 μm for both high-and low-mass YSOs. The spectra are nearly represented by the FIR colors made byIRAS flux densities at 60 and 100 μm. UsingIRAS data, we make a FIR H-R diagram of cold YSOs, the parameters of which are the FIR color and the luminosity at 60 μm. In each FIR H-R diagram of YSOs of three nearby star-forming regions, YSOs in early evolutionary phase form a fundamental sequence, along which they move with increasing of the luminosity while keeping the mass of FIR emitting envelope. We can predict the stellar masses of YSOs by using the H-R diagram.

Determination of N/O from far-infrared line observations of Galactic H II regions

view Abstract Citations (82) References (44) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Determination of N/O from Far-Infrared Line Observations of Galactic H II Regions Rubin, R. H. ; Simpson, J. P. ; Erickson, E. F. ; Haas, M. R. Abstract The procedure for deriving the N/O abundance ratio in H II regions from far-infrared (FIR) observations of [N III] and [O III] lines yields systematically much higher values than that used to obtain N/O from optical observations of [N II] and [O II] lines. The authors attribute the disparity to two effects that are not accounted for in the standard derivation of N/O by either procedure. New, more precise measurements made from NASA's Kuiper Airborne Observatory are presented of the [O III] 52, 88, and [N III] 57 μm line ratios for six H II regions. The authors apply the "geometry effect" correction as derived from their models to their own and previous FIR data. They find that the N/O ratio for most Galactic H II regions is ≡0.2 - 0.3 rather than the ≡0.05 - 0.1 derived from optical studies, thus raising the average N/O ratio from less than to greater than the solar value of 0.12. This has important implications for comparisons with theories of galactic chemical evolution and heavy element nucleosynthesis. Publication: The Astrophysical Journal Pub Date: April 1988 DOI: 10.1086/166200 Bibcode: 1988ApJ...327..377R Keywords: Abundance; Far Infrared Radiation; Galactic Structure; H Ii Regions; Infrared Spectra; Nitrogen Ions; Oxygen Ions; Astronomical Models; Computational Chemistry; Optics; Stellar Coronas; Astrophysics; NEBULAE: ABUNDANCES; NEBULAE: H II REGIONS; INFRARED: SPECTRA full text sources ADS | data products SIMBAD (18)

Determination of Spatial Distribution of Plasma Current Density by Multibeam FIR Interferometry/Polarimetry

A method is derived for inferring the point-wise current density given the shape of the outer plasma boundary ∫i neds and ∫i neB→d→s, where ne is the electron density, d→s is an increment of path length, and Bd→ is the magnetic field strength. The i is an index for the several integral traverses that are required. The integral quantities are assumed to be obtainable from far infrared (FIR) interferometer/polarimeter measurements [1], and the outer plasma boundary shape could be obtained from plasma loop probe measurements [2]. The method obtains a current density distribution that is consistent with ∇ . Bd→ = 0, ∇ × BneB→ = μ d→sj, assuming that the ne contour lines follow the B-field lines [3], [4], as well as the measured line integrals, and the measured outer plasma boundary shape. If they are available, other experimental data can also be incorporated into the analysis method. A set of data from the TEXTOR tokamak reported by Soltwisch [3] is analyzed by the method, and the results are discussed.

ChemInform Abstract: DETERMINATION OF THE CONFORMATIONAL BARRIERS TO INTERNAL ROTATION OF 3‐FLUOROPROPENE FROM FAR INFRARED AND LOW FREQUENCY RAMAN SPECTRA

Chemischer InformationsdienstVolume 16, Issue 14 Physical Organic Chemistry ChemInform Abstract: DETERMINATION OF THE CONFORMATIONAL BARRIERS TO INTERNAL ROTATION OF 3-FLUOROPROPENE FROM FAR INFRARED AND LOW FREQUENCY RAMAN SPECTRA J. R. DURIG, J. R. DURIGSearch for more papers by this authorM. ZHEN, M. ZHENSearch for more papers by this authorT. S. LITTLE, T. S. LITTLESearch for more papers by this author J. R. DURIG, J. R. DURIGSearch for more papers by this authorM. ZHEN, M. ZHENSearch for more papers by this authorT. S. LITTLE, T. S. LITTLESearch for more papers by this author First published: April 9, 1985 https://doi.org/10.1002/chin.198514046AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume16, Issue14April 9, 1985 RelatedInformation

Determination of Spatial Distribution of Plasma Electrons by Multibeam FIR Interferometry

The spatial distribution of plasma electrons in the ISX-B Tokamak has been determined by Abel-inverting vertical integral data from far infrared (FIR) laser-phase shift measurements. The calculational method for performing the Abel inversion is discussed and the results of the inversion of several sets of data are compared with Thomson scattering measurements of the pointwise electron density, and with the 2-mm interferometer measurement of the horizontal-midplane line-integral electron density. The inversion method used is essentially that described by Demas et al. This method is an extension of the method described by Yasutomo et al. The main difference is that the inversion method used here can treat plasmas with any outer boundary shape as long as the radius of the surface is single valued. In this regard it is more general than the inversion method of Wetzer, which is restricted to using an elliptical outer-plasma boundary.