Micron Spectral Region Research Articles

Многокомпонентный анализ биомаркеров в выдыхаемом воздухе методами диодной лазерной спектроскопии-=SUP=-*-=/SUP=-

Methods of multicomponent spectral analysis of exhaled air based on application of tunable diode lases were proposed for biomedical diagnostics. Simmultaneous laser based spectral analysis of the gas pairs like CO and CO2, and CO and N2O in the 4.7 micron spectral region could be used for investigation of gas exchange in studies on breathing phisiology and cardiovascular diagnostics conducted with application of different loading tests, as well as for studies in anesteziology and for on-line monitoring of ventilation-perfusion ratio. Simmultaneous analysis of NO and CO2 in 5.4 micron region could be useful fot the control of breating maneuver in studies of inflammation processes in the distal part of the lungs. Simmultaneous detection of NH3, СO2 and C2H4 near 10.5 m could be promising in studies of basal metabolizm and metabolis cycles. Simmultaneous analisis of 13СO2 and 12С O2 near 2.05 m could be used for the detection of 13СO2/12СO2 izotope ratio for izotope breath tests. The results of promising spectral region analysis and of mutual location of absorption analytical lines in these regions are presented. A possibility of simmultaneous detection of several studied molecules in the provided spectral regions was experimetally demonstrated as well as experimental laser spectra of molecular absorption were obtained. A possibility of the proposed approach in applications to analysis of trace gases in exhaled air was demonstrated.

Radiative transfer modeling of atmospheric methane for satellite measurements in the 1.66 micron spectral window

Atmospheric methane is the second most important greenhouse gas after carbon dioxide and has significant impact on the atmosphere and climate. Continuous estimation and prediction of atmospheric CH4 concentrations is important for understanding the associated global climate change. To constrain suitable spectral window and detector resolutions for satellite instruments, spectral simulations have been performed considering tropical atmospheric conditions. The study is focused on the 1.66 micron spectral region having CH4 bands that are suitable for its detection and estimation. Both CH4 concentration and spectral resolution are varied to identify optimum spectral resolution limit. The R branch peak at 1.6456 µm is found to be the most sensitive and suitable for CH4 estimation. A concentration retrieval scheme is proposed and it is interpreted that the spectral resolution should not be worse than 0.2 nm.

CHARACTERIZING WOLF-RAYET STARS IN THE NEAR- AND MID-INFRARED

We present refined color-color selection criteria for identifying Wolf-Rayet (WR) stars using available mid infrared (MIR) photometry from WISE in combination with near infrared (NIR) photometry from 2MASS. Using a sample of spectrally classified objects, we find that WR stars are well distinguished from the field stellar population in the (W1-W2) vs. (J-Ks) color-color diagram, and further distinguished from other emission line objects such as Planetary Nebulae, Be, and Cataclysmic variable stars using a combination of NIR and MIR color constraints. As proof of concept we applied the color constraints to a photometric sample in the Galactic plane, located WR star candidates, and present five new spectrally confirmed and classified WC (1) and WN (4) stars. Analysis of the 0.8-5.0 micron spectral data for a subset of known, bright WC and WN stars shows that emission lines (primarily He I) extend into the 3.0 - 5.0 micron spectral region, although their strength is greatly diminished compared to the 0.8-2.5 micron region. The WR population stands out relative to background field stars at NIR and MIR colors due to an excess continuum contribution, likely caused by free-free scattering in dense winds. Mean photometric properties of known WRs are presented and imply that reddened late-type WN and WC sources are easier to detect than earlier-type sources at larger Galactic radii. WISE W3 and W4 images of 10 Wolf Rayet stars show evidence of circumstellar shells linked to mass ejections from strong stellar winds.

LABORATORY DETERMINATION OF THE INFRARED BAND STRENGTHS OF PYRENE FROZEN IN WATER ICE: IMPLICATIONS FOR THE COMPOSITION OF INTERSTELLAR ICES

Broad infrared emission features (e.g., at 3.3, 6.2, 7.7, 8.6, and 11.3 microns) from the gas phase interstellar medium have long been attributed to polycyclic aromatic hydrocarbons (PAHs). A significant portion (10%-20%) of the Milky Way's carbon reservoir is locked in PAH molecules, which makes their characterization integral to our understanding of astrochemistry. In molecular clouds and the dense envelopes and disks of young stellar objects (YSOs), PAHs are expected to be frozen in the icy mantles of dust grains where they should reveal themselves through infrared absorption. To facilitate the search for frozen interstellar PAHs, laboratory experiments were conducted to determine the positions and strengths of the bands of pyrene mixed with H2O and D2O ices. The D2O mixtures are used to measure pyrene bands that are masked by the strong bands of H2O, leading to the first laboratory determination of the band strength for the CH stretching mode of pyrene in water ice near 3.25 microns. Our infrared band strengths were normalized to experimentally determined ultraviolet band strengths, and we find that they are generally ~50% larger than those reported by Bouwman et al. based on theoretical strengths. These improved band strengths were used to reexamine YSO spectra published by Boogert et al. to estimate the contribution of frozen PAHs to absorption in the 5-8 micron spectral region, taking into account the strength of the 3.25 micron CH stretching mode. It is found that frozen neutral PAHs contain 5%-9% of the cosmic carbon budget, and account for 2%-9% of the unidentified absorption in the 5-8 micron region.

SOFIA: first science highlights and future science potential

AbstractSOFIA, the Stratospheric Observatory for Infrared Astronomy, is a joint project between NASA and the German Aerospace Agency (DLR) to develop and operate a 2.5 m airborne telescope in a highly modified Boeing 747SP aircraft that can fly as high as 45000 feet (13.7 km). This is above 99.8 % of the precipitable water vapor which blocks much of the midand far‐infrared radiation from reaching ground‐based telescopes. In this review, we briefly discuss the characteristics of the Observatory and present a number of early science highlights obtained with the FORCAST camera in 5–40 micron spectral region and with the GREAT heterodyne spectrometer in the 130–240 micron spectral region. The FORCAST images in Orion show the discovery of a new high‐mass protostar (IRc4), while GREAT observations at 1 km s–1 velocity resolution detected velocity‐resolved, redshifted ammonia spectra at 1.81 THz in absorption against several strong farinfrared dust continuum sources, clear evidence of substantial protostellar infall onto massive (non‐ionizing) protostars. These powerful new data allow us to determine how massive stars form in our Galaxy. Another highlight is the stunning image taken by FORCAST that reveals the transient circumnuclear 1.5 pc radius (dust) ring around our Galactic center, heated by hundreds of massive stars in the young nuclear star cluster. The GREAT heterodyne spectrometer also observed the circumnuclear ring in highly excited CO rotational lines, indicative of emission from warm dense molecular gas with broad velocity structure, perhaps due to local shock heating. GREAT also made superb mapping observations of the [C II] fine structure cooling line at 158 microns, for example in M17‐SW molecular cloud–star cluster interface, observations which disprove the simple canonical photodissociation models. The much better baseline stability of the GREAT receivers (compared to Herschel HIFI) allows efficient on‐the‐fly mapping of extended [C II] emission in our galaxy and also in other nearby spiral galaxies. Of particular note is the GREAT discovery of two new molecules outside the solar system: OD (the deuterated OH hydroxyl radical) as well as mercapto radical SH, both in absorption near 1.4 THz, a frequency gap where Herschel was blind. A special highlight was the 2011 June 23 UT stellar occultation by Pluto using the HIPO high speed photometer and the FDC fast diagnostic camera. This difficult but successful observation, which was both space‐critical (within 100 km) and time‐critical (within 1 min), proved that SOFIA can be in the right place at the right time, when important transient events occur. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Impact of aerosol and thin cirrus on retrieving and validating XCO2 from GOSAT shortwave infrared measurements

Inadequate treatment of aerosol scattering can be a significant source of error when retrieving column‐averaged dry‐air mole fractions of CO2 (XCO2) from space‐based measurements of backscattered solar shortwave radiation. We have developed a retrieval algorithm, RemoTeC, that retrieves three aerosol parameters (amount, size, and height) simultaneously with XCO2. Here we evaluate the ability of RemoTeC to account for light path modifications by clouds, subvisual cirrus, and aerosols when retrieving XCO2 from Greenhouse Gases Observing Satellite (GOSAT) Thermal and Near‐infrared Sensor for carbon Observation (TANSO)‐Fourier Transform Spectrometer (FTS) measurements. We first evaluate a cloud filter based on measurements from the Cloud and Aerosol Imager and a cirrus filter that uses radiances measured by TANSO‐FTS in the 2 micron spectral region, with strong water absorption. For the cloud‐screened scenes, we then evaluate errors due to aerosols. We find that RemoTeC is well capable of accounting for scattering by aerosols for values of aerosol optical thickness at 750 nm up to 0.25. While no significant correlation of errors is found with albedo, correlations are found with retrieved aerosol parameters. To further improve the XCO2 accuracy, we propose and evaluate a bias correction scheme.Measurements from 12 ground‐based stations of the Total Carbon Column Observing Network (TCCON) are used as a reference in this study. We show that spatial colocation criteria may be relaxed using additional constraints based on modeled XCO2 gradients, to increase the size and diversity of validation data and provide a more robust evaluation of GOSAT retrievals. Global‐scale validation of satellite data remains challenging and would be improved by increasing TCCON coverage.

The wind of the M-type AGB star RT Virginis probed by VLTI/MIDI

We study the circumstellar environment of the M-type AGB star RT Vir using mid-infrared high spatial resolution observations from the ESO-VLTI focal instrument MIDI. The aim of this study is to provide observational constraints on theoretical prediction that the winds of M-type AGB objects can be driven by photon scattering on iron-free silicate grains located in the close environment (about 2 to 3 stellar radii) of the star. We interpreted spectro-interferometric data, first using wavelength-dependent geometric models. We then used a self-consistent dynamic model atmosphere containing a time-dependent description of grain growth for pure forsterite dust particles to reproduce the photometric, spectrometric, and interferometric measurements of RT Vir. Since the hydrodynamic computation needs stellar parameters as input, a considerable effort was first made to determine these parameters. MIDI differential phases reveal the presence of an asymmetry in the stellar vicinity. Results from the geometrical modeling give us clues to the presence of aluminum and silicate dust in the close circumstellar environment (< ~5 stellar radii). Comparison between spectro-interferometric data and a self-consistent dust-driven wind model reveals that silicate dust has to be present in the region between 2 to 3 stellar radii to reproduce the 59 and 63 m baseline visibility measurements around 9.8 micron. This gives additional observational evidence in favor of winds driven by photon scattering on iron-free silicate grains located in the close vicinity of an M-type star. However, other sources of opacity are clearly missing to reproduce the 10-13 micron visibility measurements for all baselines. This study is a first attempt to understand the wind mechanism of M-type AGB stars by comparing photometric, spectrometric, and interferometric measurements with state-of-the-art, self-consistent dust-driven wind models. The agreement of the dynamic model atmosphere with interferometric measurements in the 8-10 micron spectral region gives additional observational evidence that the winds of M-type stars can be driven by photon scattering on iron-free silicate grains. Finally, a larger statistical study and progress in advanced self-consistent 3D modeling are still required to solve the remaining problems.

TOTAL COLUMN METHANE RETRIEVALS USING THE TROPOSPHERIC INFRARED MAPPING SPECTROMETER OVER SUNGLINT

Abstract. Because it is a greenhouse gas, the detection of methane concentrations is a global issue. Additionally, the presence of methane is indicative of potential valuable petroleum and natural gas deposits. Therefore methane seep detection is useful for petroleum exploration around the world. The detection of methane, and other absorbing gases, over water is an issue for passive systems because one is seeking to detect an absorbing gas over an absorbing surface. The solution to this dilemma is to use the sun/sensor geometry for sun glint off of water to measure the absorbing gas over a reflecting surface, and therefore significantly increase the signal to noise of the measurement being taken. In September of 2010 Lockheed Martin performed a proof of concept by demonstrating from an airship over San Francisco Bay the capability of the Tropospheric Infrared Mapping Spectrometer's (TIMS) hyper spectral sensor to passively measure methane, CO, and water vapor over sunglint water. The Lockheed Martin prototype TIMS sensor system is a hyper spectral grating spectrometer instrument that operates in the 2.3 micron spectral region at 0.25 cm-1 resolution. The Lockheed Martin retrieval algorithm developed applies the kCARTA (kCompressed Atmospheric Radiative Transfer Algorithm) with Jacobians, with the HITRAN 2008 lineshape parameters, to retrieve the total column amount of atmospheric species along with the calibrated TIMS sensors radiometric input. A cell with known amount of methane was placed into the input to the TIMS to simulate atmospheric enhancements near the water surface. The amount in the cell was retrieved well within the uncertainty of 1% of the amount in the cell. Multi frame retrievals on data in which the cell was not placed into the input beam demonstrated 1% precision. In addition, in situ surface measurements were done over a landfill park, where measurements of methane were taken over known hotspots. This research allows for the future development of a system to measure methane, and other gases, for climate and petroleum exploration capabilities.

Spectroscopy of CH4 with a difference-frequency generation laser at 3.3 micron for atmospheric applications

The 3.25 micron spectral region is very suitable for the in situ sensing of CH4 in the troposphere and the lower stratosphere with light-weight laser sensors. Several transitions of the strong fundamental ν3 band of CH4 are revisited in this spectral region using an ultra-compact Difference-Frequency Generation (DFG) laser. Accurate intensities as well as self-broadening coefficients are reported for several manifolds that are particularly relevant to the monitoring of CH4. The study is extended to over hundred transitions reachable over the tunability range of the laser. Moreover, this DFG laser is the light source of a new, highly-compact CH4 laser spectrometer to be operated from weather balloon. The CH4 laser sensor is described and preliminary flight results are reported.

Selective principal component extraction and reconstruction: a novel method for ground based exoplanet spectroscopy

Context: Infrared spectroscopy of primary and secondary eclipse events probes the composition of exoplanet atmospheres and, using space telescopes, has detected H2O, CH4 and CO2 in three hot Jupiters. However, the available data from space telescopes has limited spectral resolution and does not cover the 2.4 - 5.2 micron spectral region. While large ground based telescopes have the potential to obtain molecular-abundance-grade spectra for many exoplanets, realizing this potential requires retrieving the astrophysical signal in the presence of large Earth-atmospheric and instrument systematic errors. Aims: Here we report a wavelet-assisted, selective principal component extraction method for ground based retrieval of the dayside spectrum of HD 189733b from data containing systematic errors. Methods: The method uses singular value decomposition and extracts those critical points of the Rayleigh quotient which correspond to the planet induced signal. The method does not require prior knowledge of the planet spectrum or the physical mechanisms causing systematic errors. Results: The spectrum obtained with our method is in excellent agreement with space based measurements made with HST and Spitzer (Swain et al. 2009b; Charbonneau et al. 2008) and confirms the recent ground based measurements (Swain et al. 2010) including the strong 3.3 micron emission.

A ground-based near-infrared emission spectrum of the exoplanet HD 189733b

Detection of molecules using infrared spectroscopy probes the conditions and compositions of exoplanet atmospheres. Water (H(2)O), methane (CH(4)), carbon dioxide (CO(2)), and carbon monoxide (CO) have been detected in two hot Jupiters. These previous results relied on space-based telescopes that do not provide spectroscopic capability in the 2.4-5.2 microm spectral region. Here we report ground-based observations of the dayside emission spectrum for HD 189733b between 2.0-2.4 microm and 3.1-4.1 microm, where we find a bright emission feature. Where overlap with space-based instruments exists, our results are in excellent agreement with previous measurements. A feature at approximately 3.25 microm is unexpected and difficult to explain with models that assume local thermodynamic equilibrium (LTE) conditions at the 1 bar to 1 x 10(-6) bar pressures typically sampled by infrared measurements. The most likely explanation for this feature is that it arises from non-LTE emission from CH(4), similar to what is seen in the atmospheres of planets in our own Solar System. These results suggest that non-LTE effects may need to be considered when interpreting measurements of strongly irradiated exoplanets.

SPITZERSPECTRAL LINE MAPPING OF PROTOSTELLAR OUTFLOWS. I. BASIC DATA AND OUTFLOW ENERGETICS

We report the results of spectroscopic mapping observations carried out toward protostellar outflows in the BHR71, L1157, L1448, NGC 2071, and VLA 1623 molecular regions using the Infrared Spectrograph (IRS) of the Spitzer Space Telescope. These observations, covering the 5.2 - 37 micron spectral region, provide detailed maps of the 8 lowest pure rotational lines of molecular hydrogen and of the [SI] 25.25 micron and [FeII] 26.0 micron fine structure lines. The molecular hydrogen lines, believed to account for a large fraction of the radiative cooling from warm molecular gas that has been heated by a non-dissociative shock, allow the energetics of the outflows to be elucidated. Within the regions mapped towards these 5 outflow sources, total H2 luminosities ranging from 0.02 to 0.75 L(solar) were inferred for the sum of the 8 lowest pure rotational transitions. By contrast, the much weaker [FeII] 26.0 micron fine structure transition traces faster, dissociative shocks; here, only a small fraction of the fast shock luminosity emerges as line radiation that can be detected with Spitzer/IRS.

Astrobiology explorer mission concepts (ABE/ASPIRE)

The AstroBiology Explorer (ABE) and the Astrobiology SPace InfraRed Explorer (ASPIRE) Mission Concepts are two missions designed to address the questions (1) “Where do we come from?” and (2) “Are we alone?” as outlined in NASA’s Origins Program. Both concepts use infrared spectroscopy to explore the identity, abundance, and distribution of molecules of astrobiological importance throughout the Universe. The ABE mission’s observational program is focused on investigating the evolution of ice and organics in all phases of the lifecycle of carbon in the universe, from stellar birth through stellar death and exogenous delivery of these compounds to planetary systems. The ASPIRE mission’s observational program expands upon ABE’s core mission and also addresses the role of silicates and gas-phase materials in interstellar organic chemistry. ABE (ASPIRE) achieves these goals using a highly sensitive, cryogenically-cooled telescope in an Earth drift-away heliocentric orbit, armed with a suite of infrared spectrometers that cover the 2.5–20 (40) micron spectral region at moderate spectral resolution ( R > 2000). ASPIRE’s spectrometer complement also includes a high-resolution ( R > 25,000) module over the 4–8 micron spectral region. Both missions’ target lists are chosen to observe a statistically significant sample of a large number of objects of varied types in support of the tasks outlined above. The ABE and ASPIRE mission lifetimes are designed to be 14 months and 3 years, respectively, both with significant cryogen and propellant lifetime margins to support an extended observing campaign. The ABE/ASPIRE Science Operations will be carried out at NASA’s Ames Research Center, and the ABE/ASPIRE database will be archived at Caltech/IPAC.

12C/13C in atmospheres of red giants and peculiar stars

We determine the carbon isotopic ratios in the atmospheres of some evolved stars in both globular clusters and the disk of our Galaxy. Analysis of 12CO and 13CO bands at 2.3 micron was carried out using fits to observed spectra of red giants and Sakurai's object (V4334 Sgr). The dependence of theoretical spectra on the various input parameters was studied in detail. The computation of model atmospheres and a detailed abundance analysis was performed in a self-consistent fashion. A special procedure for determining the best fits to observed spectra was used. We show, that globular cluster giants with [Fe/H]1.3 have a low 12C/13C = 4 ±1 abundance ratios. In the spectra of Sakurai's object (V4334 Sgr) taken between 1997-98, the 2.3 micron spectral region is veiled by hot dust emission. By fitting UKIRT spectra we determined 12C/13C = 4 ±1 for the July, 1998 spectrum. CO bands in the spectra of ultracool dwarfs are modelled as well.

ISOCAM Observations of Galactic Globular Clusters: Mass Loss along the Red Giant Branch

Deep images in the 10 micron spectral region have been obtained for five massive Galactic globular clusters, NGC 104 (=47 Tuc), NGC 362, NGC 5139 (omega Cen), NGC 6388, NGC 7078 (=M15) and NGC 6715 (=M54) in the Sagittarius Dwarf Spheroidal using ISOCAM in 1997. A significant sample of bright giants have an ISOCAM counterpart but only < 20% of these have a strong mid-IR excess indicative of dusty circumstellar envelopes. From a combined physical and statistical analysis we derive mass loss rates and frequency. We find that i) significant mass loss occurs only at the very end of the Red Giant Branch evolutionary stage and is episodic, ii) the modulation timescales must be greater than a few decades and less than a million years, and iii) mass loss occurrence does not show a crucial dependence on the cluster metallicity.

Hydrogenation of polycyclic aromatic hydrocarbons as a factor affecting the cosmic 6.2 micron emission band

While many of the characteristics of the cosmic unidentified infrared (UIR) emission bands observed for interstellar and circumstellar sources within the Milky Way and other galaxies, can be best attributed to vibrational modes of the variants of the molecular family known as polycyclic aromatic hydrocarbons (PAH), there are open questions that need to be resolved. Among them is the observed strength of the 6.2 micron (1600 cm −1) band relative to other strong bands, and the generally low strength for measurements in the laboratory of the 1600 cm −1 skeletal vibration band of many specific neutral PAH molecules. Also, experiments involving laser excitation of some gas phase neutral PAH species while producing long lifetime state emission in the 3.3 micron (3000 cm −1) spectral region, do not result in significant 6.2 micron (1600 cm −1) emission. A potentially important variant of the neutral PAH species, namely hydrogenated-PAH (H N–PAH) which exhibit intriguing spectral correlation with interstellar and circumstellar infrared emission and the 2175 Å extinction feature, may be a factor affecting the strength of 6.2 micron emission. These species are hybrids of aromatic and cycloalkane structures. Laboratory infrared absorption spectroscopy augmented by density function theory (DFT) computations of selected partially hydrogenated-PAH molecules, demonstrates enhanced 6.2 micron (1600 cm −1) region skeletal vibration mode strength for these molecules relative to the normal PAH form. This along with other factors such as ionization or the incorporation of nitrogen or oxygen atoms could be a reason for the strength of the cosmic 6.2 micron (1600 cm −1) feature.

Variations of the spectra of natural underlying surfaces in the 2-55- micrometer spectral region

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text A. A. Yakovlev , O. I. Popov, and D. P. Veselov, "Variations of the spectra of natural underlying surfaces in the 2-5.5- micrometer spectral region," J. Opt. Technol. 67, 1030- (2000) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

Calibrating Array Detectors

The development of sensitive large format imaging arrays for the infrared promises to provide revolutionary capabilities for space astronomy. For example, the Infrared Array Camera (IRAC) on SIRTF will use four 256 x 256 arrays to provide background limited high spatial resolution images of the sky in the 3 to 8 micron spectral region. In order to reach the performance limits possible with this generation of sensitive detectors, calibration procedures must be developed so that uncertainties in detector calibration will always be dominated by photon statistics from the dark sky as a major system noise source. In the near infrared, where the faint extragalactic sky is observed through the scattered and reemitted zodiacal light from our solar system, calibration is particularly important. Faint sources must be detected on this brighter local foreground. We present a procedure for calibrating imaging systems and analyzing such data. In our approach, by proper choice of observing strategy, information about detector parameters is encoded in the sky measurements. Proper analysis allows us to simultaneously solve for sky brightness and detector parameters, and provides accurate formal error estimates. This approach allows us to extract the calibration from the observations themselves; little or no additional information is necessary to allow full interpretation of the data. Further, this approach allows refinement and verification of detector parameters during the mission, and thus does not depend on a priori knowledge of the system or ground calibration for interpretation of images.

High-Temperature Optical Properties of Thin-Film Vanadium Oxides – VO2 and V2O3

AbstractThin-film vanadium dioxide (VO2) and vanadium sesquioxide (V2O3) undergo shear phase transformations at 340K and 120K, respectively. The electrical and infrared optical properties of these materials are dramatically impacted by this phase transformation. Below the phase transition temperature, both VO2 and V2O3 are “poor” electrical insulators and have minimal absorption in the infrared spectral region. Above the phase transition temperature, both VO2 and V2O3 are poor conductors and are opaque in the infrared. The infrared thermochromic properties of these materials make them interesting candidates for several optical applications.Utilization of either VO2 or V2O3 necessitates an accurate knowledge of the optical properties both above and below the phase transition temperature. This paper reports on some recent infrared ellipsometric measurements on the optical properties of these materials above the transition temperature. These measurements found that both are strongly dispersive through the 3–12 micron spectral region. In addition, the temperature dependence of the optical properties of VO2 above the transition temperature can be related to the film morphology and stoichiometry.

LWIR spectral properties of CVD diamond at cryogenic temperatures

Abstract The infrared emittance and transmittance spectra of a chemical vapor-deposited diamond substrate were determined at 4.2, 77 and 295 K. The multiphonon region was analyzed under varying degrees of spectral resolution. No variance in spectral properties over this temperature range was observed beyond measurement uncertainty. The refractive index of the material was determined in the 3–21 micron spectral region at cryogenic temperatures. The absorption coefficient was also determined and shown to vary from 11.7 cm −1 in the short wave 2 phonon region to 0.79 cm −1 at longer wavelengths. The results indicate that chemical vapor-deposited diamond possesses significant potential for use as windows, filter substrates and optical component coatings in long-wave infrared systems.