Search NASA⌕ Search

SEARCH · Search NASA

Results for “MOLECULAR OSCILLATION”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS2000

Theoretical Modeling and Computer Simulations for the Origins and Evolution of Reproducing Molecular Systems and Complex Systems with Many Interactive Parts

Our research effort has produced nine publications in peer-reviewed journals listed at the end of this report. The work reported here are in the following areas: (1) genetic network modeling; (2) autocatalytic model of pre-biotic evolution; (3) theoretical and computational studies of strongly correlated electron systems; (4) reducing thermal oscillations in atomic force microscope; (5) transcription termination mechanism in prokaryotic cells; and (6) the low glutamine usage in thennophiles obtained by studying completely sequenced genomes. We discuss the main accomplishments of these publications.

Liang, Shoudan↗
NASA NTRS1980

Collisional narrowing by polyatomic buffer gases in an optically pumped CH3F laser

The gain linewidth of an optically pumped CH3F molecular laser is observed with the addition of various polyatomic buffer gases. This is interpreted as collisional (Dicke) narrowing. The measurement is the first observation of collisional narrowing by polyatomic buffer gases. It is also the first observation of the effect in a laser oscillator. The effect was observed using a heterodyne mixing technique at the laser emission frequency of 604 GHz. Collision cross sections for SF6-CH3F and CS2-CH3F are obtained.

Lawandy, N. M.↗
NASA NTRS1988

A TEOM (tm) particulate monitor for comet dust, near Earth space, and planetary atmospheres

Scientific missions to comets, near earth space, and planetary atmospheres require particulate and mass accumulation instrumentation for both scientific and navigation purposes. The Rupprecht & Patashnick tapered element oscillating microbalance can accurately measure both mass flux and mass distribution of particulates over a wide range of particle sizes and loadings. Individual particles of milligram size down to a few picograms can be resolved and counted, and the accumulation of smaller particles or molecular deposition can be accurately measured using the sensors perfected and toughened under this contract. No other sensor has the dynamic range or sensitivity attained by these picogram direct mass measurement sensors. The purpose of this contract was to develop and implement reliable and repeatable manufacturing methods; build and test prototype sensors; and outline a quality control program. A dust 'thrower' was to be designed and built, and used to verify performance. Characterization and improvement of the optical motion detection system and drive feedback circuitry was to be undertaken, with emphasis on reliability, low noise, and low power consumption. All the goals of the contract were met or exceeded. An automated glass puller was built and used to make repeatable tapered elements. Materials and assembly methods were standardized, and controllers and calibrated fixtures were developed and used in all phases of preparing, coating and assembling the sensors. Quality control and reliability resulted from the use of calibrated manufacturing equipment with measurable working parameters. Thermal and vibration testing of completed prototypes showed low temperature sensitivity and high vibration tolerance. An electrostatic dust thrower was used in vacuum to throw particles from 2 x 10(exp 6) g to 7 x 10(exp -12) g in size. Using long averaging times, particles as small as 0.7 to 4 x 10(exp 11) g were weighted to resolutions in the 5 to 9 x 10(exp -13) g range. The drive circuit and optics systems were developed beyond what was anticipated in the contract, and are now virtually flight prototypes. There is already commercial interest in the developed capability of measuring picogram mass losses and gains. One area is contamination and outgassing research, both measuring picogram losses from samples and collecting products of outgassing.

Source record↗
NASA NTRS1982

Molecular processes in comets

Potential energy curves for the two lowest 2 sigma- states of OH are computed at the configuration-interaction level using four different basis sets. Electronic transition dipole moments connecting the excited 1 2 sigma- and 2(D) 2 sigma- states with each other and with he ground X2pi state are presented as functions of internuclear distance. The theoretical absorption oscillator strengths for the D 2 sigma-(v prime=0) reverser to X 2pi (v prime prime=0) transition are in good agreement with the empirical value derived from astronomical measurements. The photodissociation cross sections for absorption rom the v prime prime=0,1, and levels of the ground state into the continuum of the 1 2 sigma- state are calculated, and the interstellar and cometary photodissociation rates are derived.

Dalgarno, A.↗
NASA NTRS1997

Molecular Dynamics Simulations of Laser Powered Carbon Nanotube Gears

Dynamics of laser powered carbon nanotube gears is investigated by molecular dynamics simulations with Brenner's hydrocarbon potential. We find that when the frequency of the laser electric field is much less than the intrinsic frequency of the carbon nanotube, the tube exhibits an oscillatory pendulam behavior. However, a unidirectional rotation of the gear with oscillating frequency is observed under conditions of resonance between the laser field and intrinsic gear frequencies. The operating conditions for stable rotations of the nanotube gears, powered by laser electric fields are explored, in these simulations.

Srivastava, Deepak↗
NASA NTRS1992

Electronic energy gap of molecular hydrogen from electrical conductivity measurements at high shock pressures

Electrical conductivities were measured for liquid D2 and H2 shock compressed to pressures of 10-20 GPa (100-200 kbar), molar volumes near 8 cu cm/mol, and calculated temperatures of 2900-4600 K. The semiconducting energy gap derived from the conductivities is 12 eV, in good agreement with recent quasi-particle calculations and with oscillator frequencies measured in diamond-anvil cells.

Nellis, W. J.↗
NASA NTRS1993

Molecular-beam spectrum of the 970/cm Fermi triad of CF3CH3

A tunable MW-sideband CO2 laser is used with an electric-resonance optothermal spectrometer to investigate the IR spectrum of CF3CH3 near 970/cm. A Fermi-coupled triad of states is observed, resulting from the interactions of 2nu6+nu11 and nu5+nu12 with the fundamental vibration, nu10, which is assumed to carry the oscillator strength in this region. The high resolution (about 3 MHz) of the spectrometer allows the observation of tunneling splittings associated with the nu6 torsional vibration. These splittings are used to identify the torsional character of the states observed. At the normal-mode level the nu10 and nu5+nu12 states are found to be nearly degenerate and interacting by an anharmonic matrix element of about 3/cm. The present investigation illustrates the utility of using resolved torsional splittings to unravel complex vibrational couplings in molecules.

Fraser, G. T.↗
NASA NTRS1973

Monitoring atmospheric pollutants with a heterodyne radiometer transmitter-receiver

The presence of selected atmospheric pollutants can be determined by transmitting an infrared beam of proper wavelength through the atmosphere, and detecting the reflections of the transmitted beam with a heterodyne radiometer transmitter-receiver using part of the laser beam as a local oscillator. The particular pollutant and its absorption line strength to be measured are selected by the laser beam wave length. When the round-trip path for the light is known or measured, concentration can be determined. Since pressure (altitude) will affect the shape of the molecular absorption line of a pollutant, tuning the laser through a range of frequencies, which includes a part of the absorption line of the pollutant of interest, yields pollutant altitude data from which the altitude and altitude profile is determined.

Menzies, R. T.↗
NASA NTRS2009

Synthesis of Submillimeter Radiation for Spectroscopy

The frequency-multiplier submillimeter spectrometer (FMSS) is a laboratory apparatus for far-infrared molecular spectroscopy, embodying several advances over prior such apparatuses. The most innovative part of the FMSS is a source of monochromatic submillimeter- wavelength radiation that can be tuned over a wide frequency range, as needed for trace gas analyses and molecular- structure studies for which such apparatuses are typically used. The radiation source features a modular design and is built mostly from commercially available components. It includes a computer-controlled radio-frequency synthesizer, amplifiers, and frequency multipliers of a type heretofore used in local oscillators for heterodyne far-infrared receivers. In conjunction with the rest of the apparatus, this source makes it possible to perform measurements over large portions of the submillimeter-wavelength spectrum with resolution, accuracy, and sensitivity greater than those achievable in Fourier-transform infrared spectroscopy. In comparison with prior laboratory submillimeter- wavelength radiation sources, this source is much lighter in weight, less cumbersome, less power-hungry, and capable of sustained operation with less intervention by laboratory personnel. Also, unlike some prior submillimeter-wavelength sources, this source does not require a high-voltage power source. As shown in more detail in the figure, the radiation source includes a sweep frequency synthesizer connected to an external waveform generator, the output of which is used as a reference signal. The synthesizer is computer-controlled through a standard general-purpose interface bus (GPIB) and is operated in phase-locked continuous- wave mode for all measurements. The synthesizer output ranges in frequency from 11 to 18 GHz. For suppression of frequency spurs and harmonics, the output of the frequency synthesizer is fed through a tunable yttrium iron garnet (YIG) filter, which is swept in frequency simultaneously with the frequency synthesizer.

Maiwald, Frank↗
NASA NTRS1993

The distribution of Martian ground ice at other epochs

The past orbital evolution of Mars is examined in relation to changes in ice stability as well as the condensation, sublimation, and diffusion of atmospheric water in an exchange with the regolith. The Martian obliquity has undergone significant oscillations in its recent past. During periods of high obliquity, the solar energy would have been distributed such that the equatorial and midlatitude regions would have been colder that at present and the polar regions would have been warmer. Warmer polar regions would result in the sublimation of more polar cap water into the atmosphere and thus higher atmospheric water abundances. This combination of effects would have resulted in ground ice being stable globally. During periods of low obliquity the opposite would have occurred. Modeling results of the regolith thermal behavior and the molecular diffusion of water vapor within the regolith and in exchange with the atmosphere have shown significant quantities of ground ice can form at all latitudes within the top 50 cm to 1 m of the regolith during periods of high obliquity. The amount of ice that forms can be as much as the regolith pores can hold. During low obliquity most or all of this ice sublimes and diffuses away. Below this depth a longer-term stability is observed at some latitudes where ice steadily increases in concentration regardless of orbital oscillations that occur.

Mellon, M. T.↗
NASA NTRS1993

Models of thermal relaxation mechanics for particle simulation methods

A comparative study is conducted of the simulation of molecular vibrational relaxation in rarefied flows by means of existing models and a novel phenomenological microscopic model. This improved technique iterates between translation-rotation and rotation-vibration exchanges; equilibrium is in this way promoted if the model for the latter process is compatible with quantized oscillators. The iteration-equipartition model retains computational simplicity and promotes thermal equilibrium, even in the case of nondegenerate anharmonic quantized oscillators and multispecies gas mixtures.

Haas, Brian L.↗
NASA NTRS1982

Effective photodissociation cross sections for molecular oxygen and nitric oxide in the Schumann-Runge bands

Accurate calculations of the atmospheric opacity and the photodissociation rate of molecular oxygen in the Schumann-Runge bands (175-205) are necessary for modeling chemistry in the terrestrial upper atmosphere. The present investigation is concerned with a single simple parameterization of effective cross sections which can be used to calculate both O2 opacity and dissociation rates. Use is made of a zenith angle dependent factor which accounts for variations shown in detailed calculations. The conducted analysis is based on the results of Frederick and Hudson (1980). Attention is given to molecular oxygen effective cross sections and nitric oxide effective cross sections. It is found that the depth of the atmosphere to which solar radiation in the 175-200 nm spectral region penetrates is a sensitive function of the rotational line widths in the Schumann-Runge bands. The oscillator strength for each band measures the cross section integrated over the band while the line width determine how the absorption is distributed in wavenumber.

Allen, M.↗
NASA NTRS2012

Frequency Correction for MIRO Chirp Transformation Spectroscopy Spectrum

This software processes the flyby spectra of the Chirp Transform Spectrometer (CTS) of the Microwave Instrument for Rosetta Orbiter (MIRO). The tool corrects the effect of Doppler shift and local-oscillator (LO) frequency shift during the flyby mode of MIRO operations. The frequency correction for CTS flyby spectra is performed and is integrated with multiple spectra into a high signal-to-noise averaged spectrum at the rest-frame RF frequency. This innovation also generates the 8 molecular line spectra by dividing continuous 4,096-channel CTS spectra. The 8 line spectra can then be readily used for scientific investigations. A spectral line that is at its rest frequency in the frame of the Earth or an asteroid will be observed with a time-varying Doppler shift as seen by MIRO. The frequency shift is toward the higher RF frequencies on approach, and toward lower RF frequencies on departure. The magnitude of the shift depends on the flyby velocity. The result of time-varying Doppler shift is that of an observed spectral line will be seen to move from channel to channel in the CTS spectrometer. The direction (higher or lower frequency) in the spectrometer depends on the spectral line frequency under consideration. In order to analyze the flyby spectra, two steps are required. First, individual spectra must be corrected for the Doppler shift so that individual spectra can be superimposed at the same rest frequency for integration purposes. Second, a correction needs to be applied to the CTS spectra to account for the LO frequency shifts that are applied to asteroid mode.

Lee, Seungwon↗
NASA NTRS2003

A Gravity-Responsive Time-Keeping Protein of the Plant and Animal Cell Surface

The hypothesis under investigation was that a ubiquinol (NADH) oxidase protein of the cell surface with protein disulfide-thiol interchange activity (= NOX protein) is a plant and animal time-keeping ultradian (period of less than 24 h) driver of both cell enlargement and the biological clock that responds to gravity. Despite considerable work in a large number of laboratories spanning several decades, this is, to my knowledge, our work is the first demonstration of a time-keeping biochemical reaction that is both gravity-responsive and growth-related and that has been shown to determine circadian periodicity. As such, the NOX protein may represent both the long-sought biological gravity receptor and the core oscillator of the cellular biological clock. Completed studies have resulted in 12 publications and two issued NASA-owned patents of the clock activity. The gravity response and autoentrainment were characterized in cultured mammalian cells and in two plant systems together with entrainment by light and small molecules (melatonin). The molecular basis of the oscillatory behavior was investigated using spectroscopic methods (Fourier transform infrared and circular dichroism) and high resolution electron microscopy. We have also applied these findings to an understanding of the response to hypergravity. Statistical methods for analysis of time series phenomena were developed (Foster et al., 2003).

Morre, D. James↗
NASA NTRS1983

Measurement of the linear viscoelastic behavior of antimisting kerosene

Measurements of dynamic viscoelastic properties in very small oscillating shear deformations was made on solutions of a jet fuel, Jet A, containing an antimisting polymeric additive, FM-9. A few measurements were also made on solutions of FM-9 in a mixed solvent of mineral oil, Tetralin, and 0-terphenyl. Two samples of FM-9 had approximate number-average molecular weights of 12,000,000 and 8,100,000 as deduced from analysis of the measurements. The ranges of variables were 2.42 to 4.03 g/1 in concentration (0.3 to 0.5% by weight), 1 to 35 in temperature, 1.3 to 9.4 cp in solvent viscosity, and 103 to 6100 Hz in frequency. Measurements in the Jet A solvent were made both with and without a modifying carrier. The results were compared with the Zimm theory and the viscoelastic behavior was found to resemble rather closely that of ordinary non-polar polymers in theta solvents. The relation of the results to the antithixotropic behavior of such solutions a high shear rates is discussed in terms of intramolecular and intermolecular interactions.

Ferry, J. D.↗
NASA NTRS1981

433 micron laser heterodyne observations of galactic CO from Mauna Kea

A submillimeter heterodyne radiometer, developed for astronomical applications, uses an optically pumped laser local oscillator and a quasi-optical Schottky diode mixer. The resultant telescope-mounted system, which has a noise temperature less than 4000 K (double sideband) and high frequency and spatial resolution, has been used to detect the J = 6 to 5 rotational transition of carbon monoxide at 434 micrometers in the Orion molecular clouds. The measurements, when compared with previous millimeter-wave data, indicate that the broad carbon monoxide emission feature is produced by an optically thin gas whose temperature exceeds 180 K.

Buhl, D.↗
NASA NTRS1981

Detection of the J = 6 - 5 transition of carbon monoxide

The J = 6 - 5 rotational transition of carbon monoxide has been detected in emission from the KL 'plateau source' in the Orion molecular cloud. The corrected peak antenna temperature is 100 K, and the FWHM line width is 26 km/sec. These observations were carried out using the 3 m telescope of the NASA IRTF (Infrared Telescope Facility) on Mauna Kea, Hawaii, and constitute the first astronomical data obtained at submillimeter wavelengths with a heterodyne system using a laser local oscillator. The data support the idea that the high-velocity dispersion CO in Orion is optically thin and set a lower limit to its temperature of approximately 180 K.

Goldsmith, P. F.↗
NASA NTRS1984

The calculation of molecular Eigen-frequencies

A method of determining molecular eigen-frequencies based on the function of Einstein expressing the variation of the atomic heat of various elements is proposed. It is shown that the same equation can be utilized to calculate both atomic heat and optically identifiably eigen-frequencies - at least to an order of magnitude - suggesting that in both cases the same oscillating structure is responsible.

Lindemann, F. A.↗