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NASA NTRS1975

Remote measurement of ocean temperature from depolarization in Raman scattering

Ocean temperatures may be mapped in three dimensions from an aircraft down to depths of 2 to 4 attenuation lengths by monitoring Raman radiation backscattered from a laser beam. This paper describes laboratory experiments on the temperature dependence of Raman spectra of saline solutions and calculations of the expected performance of a field system. The Raman technique is of greatest potential utility in coastal and estuarine waters where gradients are relatively high. It is estimated that seawater temperature may be measured to a statistical precision of 0.5 C at depths to four attenuation lengths in two meter water, using one Joule of transmitted laser energy.

Chang, C. H.↗

NASA NTRS1993

Thermal processing of omicron-terphenyl - A Raman study

Raman spectra from omicron-terphenyl sealed in glass capillary tubes were acquired over temperatures ranging from 233 to 343 K. Over this temperature range, omicron-terphenyl can exist in the solid-crystalline, molten, supercooled-liquid, and amorphous-glassy states. Representative structure-sensitive spectra are presented along with a qualitative description. The lattice spectral feature occurring at a Raman shift of 123/cm displays abrupt changes in profile and intensity as melting and glass transition occur. The intensity ratio of the C-C stretching 996/cm line and C-H stretching line at 1008/cm displays a change related to the transformation of the ordered-crystalline phase to the disordered-liquid or glassy state. At a Raman shift of 1162/cm the solid-crystalline state shows a splitting due to the effect of the crystal field. The possibility of using these structure-sensitive Raman characteristics for in situ diagnostics during materials processing is discussed.

Biswas, A.↗

NASA NTRS2001

Remote Pulsed-Laser Raman Spectroscopy System for Mineral Analysis

We have measured Raman spectra of carbonate, silicate, and hydrous silicate and sulfate minerals, our new remote-pulsed Raman system, indicating that it can be used to analyze the minerals on planetary surfaces to a distance of 10 to 66 meters. Additional information is contained in the original extended abstract.

Sharma, S. K.↗

NASA NTRS2002

High-Pressure Gaseous Burner (HPGB) Facility Completed for Quantitative Laser Diagnostics Calibration

A gas-fueled high-pressure combustion facility with optical access, which was developed over the last 2 years, has just been completed. The High Pressure Gaseous Burner (HPGB) rig at the NASA Glenn Research Center can operate at sustained pressures up to 60 atm with a variety of gaseous fuels and liquid jet fuel. The facility is unique as it is the only continuous-flow, hydrogen-capable, 60-atm rig in the world with optical access. It will provide researchers with new insights into flame conditions that simulate the environment inside the ultra-high-pressure-ratio combustion chambers of tomorrow's advanced aircraft engines. The facility provides optical access to the flame zone, enabling the calibration of nonintrusive optical diagnostics to measure chemical species and temperature. The data from the HPGB rig enables the validation of numerical codes that simulate gas turbine combustors, such as the National Combustor Code (NCC). The validation of such numerical codes is often best achieved with nonintrusive optical diagnostic techniques that meet these goals: information-rich (multispecies) and quantitative while providing good spatial and time resolution. Achieving these goals is a challenge for most nonintrusive optical diagnostic techniques. Raman scattering is a technique that meets these challenges. Raman scattering occurs when intense laser light interacts with molecules to radiate light at a shifted wavelength (known as the Raman shift). This shift in wavelength is unique to each chemical species and provides a "fingerprint" of the different species present. The facility will first be used to gather a comprehensive data base of laser Raman spectra at high pressures. These calibration data will then be used to quantify future laser Raman measurements of chemical species concentration and temperature in this facility and other facilities that use Raman scattering.

Nguyen, Quang-Viet↗

NASA NTRS2008

Low-Resolution Raman-Spectroscopy Combustion Thermometry

A method of optical thermometry, now undergoing development, involves low-resolution measurement of the spectrum of spontaneous Raman scattering (SRS) from N2 and O2 molecules. The method is especially suitable for measuring temperatures in high pressure combustion environments that contain N2, O2, or N2/O2 mixtures (including air). Methods based on SRS (in which scattered light is shifted in wavelength by amounts that depend on vibrational and rotational energy levels of laser-illuminated molecules) have been popular means of probing flames because they are almost the only methods that provide spatially and temporally resolved concentrations and temperatures of multiple molecular species in turbulent combustion. The present SRS-based method differs from prior SRS-based methods that have various drawbacks, a description of which would exceed the scope of this article. Two main differences between this and prior SRS-based methods are that it involves analysis in the frequency (equivalently, wavelength) domain, in contradistinction to analysis in the intensity domain in prior methods; and it involves low-resolution measurement of what amounts to predominantly the rotational Raman spectra of N2 and O2, in contradistinction to higher-resolution measurement of the vibrational Raman spectrum of N2 only in prior methods.

Nguyen, Quang-Viet↗

NASA NTRS2018

PIV and Rotational Raman-Based Temperature Measurements for CFD Validation in a Single Injector Cooling Flow

NASA's Turbulent Heat Flux (THX) task under the Transformational Tools & Technologies project is focused on acquiring benchmark temperature and velocity data in turbulent shear layers for validation of computational fluid dynamics (CFD) codes. Standard CFD turbulence models lack the ability to accurately calculate a number of fundamental flow phenomena, including the turbulent transport of heat. In nearly all production class Reynolds-averaged Navier-Stokes (RANS) CFD codes, a gradient-diffusion approximation is used whereby a constant turbulent Prantdl number, Prt, is used to relate an eddy viscosity calculated for the momentum terms, to the turbulent heat flux terms. The default in most CFD codes is Prt = 0.9, however this is not representative of all flows. As discussed in Yoder et al. (2015) and Reynolds (1974), Prt = 0.7 is felt to be more appropriate for jets. Recent work, as discussed in Yoder (2016a), has explored more complex formulations including variable turbulent Prantdl number models. PARTICLE IMAGE VELOCIMETRY; TEMPERATURE MEASURING INSTRUMENTS; FILM COOLING; HIGH TEMPERATURE GASES; COMPUTATIONAL FLUID DYNAMICS; PREDICTION ANALYSIS TECHNIQUES; TURBULENCE MODELS; RAMAN SPECTRA; VELOCITY; MACH NUMBER; GAS TURBINE ENGINES; NOZZLE FLOW; THERMOCOUPLES; LASER INDUCED FLUORESCENCE; COOLING FLOWS (ASTROPHYSICS); RAMAN SPECTROSCOPY; HEAT FLUX

Wernet, Mark P.↗

NASA NTRS2000

Remote Raman System for Planetary Landers: Data Reduction and Analysis

Raman spectroscopy is typically envisioned as an in situ analysis technique. Raman spectra measured remotely (10s of meters) from a planetary lander can be calibrated to spectral radiance and the Raman scattering efficiency can be determined.

Horton, K. A.↗

NASA NTRS1986

Infrared absorption and emission characteristics of interstellar PAHs

The mid-infrared interstellar emission spectrum with features at 3.28, 6.2, 7.7, 8.7 and 11.3 microns is discussed in terms of the Polycyclic Aromatic Hydrocarbon (PAH) hypothesis, which is based on the suggestive, but inconclusive comparison between the interstellar emission spectrum with the infrared absorption and Raman spectra of a few PAHs. The fundamental vibrations of PAHs and PAH-like species which determine the IR and Raman properties are discussed. Interstellar IR band emission is due to relaxation from highly vibrationally excited PAHs excited by ultraviolet photons. The excitation/emission process is described and the IR fluorescence from one PAH, chrysene, is traced. Generally, there is sufficient energy to populate several vibrational levels in each mode. Molecular vibrational potentials are anharmonic and emission from these higher levels will fall at lower frequencies and produce weak features to the red of the stronger fundamentals. This process is also described and can account for some spectroscopic details of the interstellar emission spectra previously unexplained. Analysis of the interstellar spectrum shows that PAHs contain between 20 and 30 carbon atoms are responsible for the emission.

Barker, J. R.↗

NASA NTRS1987

Infrared absorption and emission characteristics of interstellar PAHs

Allamandola, L. J.↗

NASA NTRS1986

Raman spectroscopy of gases with a Fourier transform spectrometer - The spectrum of D2

Fourier transform spectrometry (FTS) is presently used to record the spontaneous incoherent laser Raman spectra of gases. The high resolution, sensitivity, calibration accuracy and spectral coverage achieved demonstrate the viability of FTS for Raman spectroscopy. Attention is given to the coefficients obtained by fitting measurements obtained from the spectrum of D2, containing both v = 0-0 and 1-0 transitions, to the Dunham (1932) expansion of the vibration-rotation energy levels.

Jennings, D. E.↗

NASA NTRS1991

Raman Spectral Observation of a "New Phase" Observed in Nickel Electrodes Cycled to Failure

A "new phase" is reported in nickel electrodes from Ni/H boilerplate cells which were cycled to failure in electrolyte of variable kOH concentration. Raman spectra clearly show the presence of this phase, and these spectra have been used to quantify the amounts present in these electrodes (in the volume sampled by the laser beam) Raman spectroscopy has been found to be capable of differentiating the various phases which can be present in nickel .This differentiation is possible because of the structural variation observed for these phases. Ten of twelve electrodes examined contain at least some of this new phase. The presence of this "new phase" correlates with cell failure, and it is proposed that the presence of this phase may play a role in early electrode failure.

Loyselle, P. L.↗

NASA NTRS1977

The vibrational spectrum and lattice dynamics of polycrystalline ammonium hydrosulfide

The infrared spectra of alkali metal and ammonium hydrosulfides have been recorded from wavenumbers of 200 to 4000 at liquid nitrogen temperatures, and the Raman spectra of these substances have been recorded from wavenumbers of 0 to 4000 over the temperature range 83-390 K. No evidence of a second solid phase was obtained. Internal and external fundamentals were assigned, in detail, based on selection rules, isotopic frequency shifts, and analogy with structurally similar salts. Barriers to anion and cation reorientation of 3.8 and 1.9 kcal/mole, respectively, have been calculated from librational assignments. The implications of the infrared spectrum of ammonium hydrosulfide for the possible spectroscopic detection of this substance in the atmosphere of the planet Jupiter are discussed.

Bragin, J.↗

NASA NTRS1971

Vibrational spectra and structure of dimethylaminodichlorophosphine.

Evaluation of the infrared spectra of dimethylaminodichlorophosphine and dimethylaminodichlorophosphine-d sub 6 recorded from 4000 to 33 per cm in the gas and solid phases. The Raman spectra of the liquid and solid phases for both compounds were also recorded. The spectra were consistent with the presence of only one isomer over the range of phases and temperatures studied. Available experimental data were discussed in connection with the spectra, and it is concluded that the molecule exists in the gauche conformer with the PNC2 portion of the molecule planar. A vibrational assignment is proposed for the molecule.

Durig, J. R.↗

NASA NTRS2005

Chirality Characterization of Dispersed Single Wall Carbon Nanotubes

Raman scattering and optical absorption spectroscopy are used for the chirality characterization of HiPco single wall carbon nanotubes (SWNTs) dispersed in aqueous solution with the surfactant sodium dodecylbenzene sulfonate. Radial breathing mode (RBM) Raman peaks for semiconducting and metallic SWNTs are identified by directly comparing the Raman spectra with the Kataura plot. The SWNT diameters are calculated from these resonant peak positions. Next, a list of (n, m) pairs, yielding the SWNT diameters within a few percent of that obtained from each resonant peak position, is established. The interband transition energies for the list of SWNT (n, m) pairs are calculated based on the tight binding energy expression for each list of the (n, m) pairs, and the pairs yielding the closest values to the corresponding experimental optical absorption peaks are selected. The results reveal that (1, 11), (4, 11), and (0, 11) as the most probable chiralities of the semiconducting nanotubes. The results also reveal that (4, 16), (6, 12) and (8, 8) are the most probable chiralities for the metallic nanotubes. Directly relating the Raman scattering data to the optical absorption spectra, the present method is considered the simplest technique currently available. Another advantage of this technique is the use of the E(sup 8)(sub 11) peaks in the optical absorption spectrum in the analysis to enhance the accuracy in the results.

Namkung, Min↗

NASA NTRS1990

Deposition of diamondlike films by electron cyclotron resonance microwave plasmas

Hard a-C:H films have been deposited through electron cyclotron resonance (ECR) microwave plasma decomposition of CH4 diluted with H2 gas. It has been found that hard diamondlike films could only be produced under a RF-induced negative self-bias of the substrate stage. Raman spectra indicate the deposition of two distinct film types: one film type exhibiting well-defined bands at 1360 and 1580/cm and another displaying a broad Raman peak centered at approximately 1500/cm. Variation of the mirror magnetic-field profile of the ECR system was examined, demonstrating the manipulation of film morphology through the extraction of different ion energies.

Pool, F. S.↗

NASA NTRS2004

Mars Mineral Spectroscopy Web Site: A Resource for Remote Planetary Spectroscopy

A web site dedicated to Mars Mineral Spectroscopy has been established at http://www.mtholyoke.edu/go/mars. Its goal is to provide an easily accessible data set of Mossbauer spectra of minerals collected over a range of temperatures, to provide suitable analog spectra for data acquired on remote surfaces such as Mars. Complementing these data (eventually) will be both reflectance FTIR data, collected at Brown University's RELAB facility, and Raman spectra to be collected by Jill Pasteris at Washington University St. Louis. Through our Education link, we provide information for those wishing to learn about how Mossbauer and other types of spectroscopy work. Our emphasis is to study only well-characterized mineral samples that represent typical rock-forming occurrences such as might exist on Mars and other terrestrial bodies in our solar system.

Dyar, M. D.↗

NASA NTRS1993

High-pressure infrared sepctra of alpha-quartz, coesite, stishovite and silica glass

High-pressure infrared absorption spectra of alpha-quatz, coesite, stishovite, and SiO2 glass are consistent with the primary compression mechanism of the initially tetrahedrally bonded phases being the bending of the Si-O-Si angle at pressures less than 10-20 GPa. At higher pressures, up to 40 GPa, we observe a decline in the intensity of the infrared SiO4 asymmetric-stretching vibrations of all three phases, with an increase in the relative amplitude between 700 and 900/cm. This change in intensities is attributed to an increase in the average coordination number of silicon through extreme distortion of tetrahedra. At pressures above approximately 20 GPa, the low-pressure crystalline polymorphs gradually become amorphous, and the infrared spectra provide evidence for an increase in silicon coordination in these high-density amorphous phases. The pressure-amorphized samples prepared from quartz and coesite differ structurally both from each other and from silica glass that has been compressed, and the high pressure spectra indicate that these materials are considerably more disordered than stishovite under comparable pressure conditions. Average mode Grueneisen parameters calculated for quartz, stishovite and fused silica from both infrared and Raman spectra are compatible with the corresponding thermodynamic value of the Grueneisen parameter, however, that of coesite is significantly discrepant.

Williams, Q.↗

NASA NTRS2012

Near-Infrared (NIR) Raman Spectroscopy of Precambrian Carbonate Stromatolites with Post-Depositional Organic Inclusions

Raman spectroscopy has promising potential for future Mars missions as a non-contact detection technique for characterizing organic material and mineralogy. Such a capability will be useful for selecting samples for detailed analysis on a rover and for selecting samples for return to Earth. Stromatolites are important evidence for the earliest life on Earth and are promising targets for Mars investigations. Although constructed by microorganisms, stromatolites are organo-sedimentary structures that can be large enough to be discovered and investigated by a Mars rover. In this paper, we report the Raman spectroscopic investigations of the carbonate mineralogy and organic layering in a Precambrian (;1.5 Gyr old) stromatolite from the Crystal Spring Formation of Southern California. Ultraviolet (UV: 266 nm), visible (514 nm, 633 nm), and near-infrared (NIR: 785 nm, 1064 nm) Raman spectra are presented. We conclude that 1064 nm excitation is the optimal excitation wavelength for avoiding intrinsic fluorescence and detecting organic carbon within the carbonate matrix. Our results confirm that NIR Raman spectroscopy has important applications for future Mars missions.

Tanaka, Zuki↗