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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.

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At least 361 records · Page 20
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NASA NTRS1992

A possible detection of infrared emission from carbon monoxide in Comet Austin (1989c1)

A cryogenic IR echelle grating spectrometer has been used to probe the nu = 1-0 rovibrational band of the CO molecule in Comet Austin. Line emission has been detected at the Doppler-shifted frequency expected for the cometary P(3) line, in scans which are noted to cover only the first 3000 sec of May 16, 1990 observations; this is suggested to be due to an outburst of comparable duration. No detections were made of the P(2) line, which was predicted by models to occur at the 3.5 sigma level even for relatively high coma temperatures. If the outburst was accompanied by enhanced dust production, an increase by a factor of 2.5 is consistent with the present observational data and CO/dust may have been enriched in the outbursting volume relative to the remainder of the nucleus.

Disanti, Michael A.↗
NASA NTRS1991

Airborne tunable diode laser sensor for high-precision concentration and flux measurements of carbon monoxide and methane

An airborne tunable diode laser instrument is described that is capable of operating in two measurement modes. One mode provides high precision (0.1 percent CH4; 1 percent CO) measurements of CH4 and CO with a 5 second response time, and a second mode achieves the very fast response time that is necessary to make airborne eddy correlation flux measurements. Examples of data from atmospheric expeditions of the Global Tropospheric Experiment are presented.

Sachse, G. W.↗
NASA NTRS1992

Venus mesospheric winds and the carbon monoxide bulge

Recently, our group mapped the CO absorption lines on the disk of Venus in 1988 using the synthetic aperture array at the Owens Valley Radio Observatory. Observations were make in the (0-1) rotational transition of CO at 115 GHz, or a wavelength of 2.6 mm. Systematic variations in the Doppler shifts of the lines (particularly near the limbs) enable the group to directly map the wind field at 100 plus or minus 10 km, the peak altitude for the experimental weighting functions used. These measurements show that the winds are indeed of the order of a 100 m/s at this altitude. Previously, many had assumed that the vertical wind profile would quickly fall to zero above the cloud tops, due to cyclostrophic breakdown. This work is reviewed.

Gurwell, Mark A.↗
NASA NTRS1992

A surface brightness correlation between carbon monoxide and nonthermal radio continuum emission in the galaxy

The relation between the projected face-on velocity-integrated CO (1-0) brightness ICO and the 20 cm nonthermal radio continuum brightness T20 is examined as a function of radius in the Galactic disk. Averaged in 1 kpc annuli, the ratio ICO/T20 is nearly constant with a mean value of 1.51 +/- 0.34 km/s from 2 to 10 kpc. The manner in which ICO and T20 are derived for the Galaxy is different in several significant respects from the more direct observational determinations possible in nearby galaxies. The fact that the Galaxy also follows this correlation further strengthens the generality of the result.

Allen, R. J.↗
NASA NTRS1992

Carbon monoxide and methane in the North American Arctic and Subarctic troposphere - July-August 1988

Enhanced concentrations of CH4 in the unpolluted atmospheric mixed layer over both Arctic and subarctic tundra landscapes are documented here using data from the NASA Arctic Boundary Layer Expedition (ABLE 3A). The CH4 concentration gradients were determined mainly by interactions of biogenic emission from wet tundra and turbulent mixing proceses. The gradient were most frequently associated with intrusion of upper tropospheric or stratospheric air into the midtroposphere, emissions from forest and tundra fires, and long-range transport of enhanced concentration of these gases from unidentified sources. Summertime haze layers exhibited midtropospheric enhancements of CH4 similar to those measured in winter Arctic events. The observations confirm the importance of Arctic and Subarctic wetland environments as a regional source of global atmospheric CH4.

Harriss, Robert C.↗
NASA NTRS1993

High-resolution absorption cross section measurements of carbon monoxide at 20 K between 96.7 and 98.8 nanometers

Photoabsorption cross sections for five CO bands, at wavelengths between 96.7 and 98.8 nm, have been measured at high-resolution in a supersonic jet-cooled source at the Photon Factory synchrotron facility. New integrated cross sections are reported for the K-X, L(prime)-X, and L-X bands. Low-temperature spectra of the J-X and W-X bands, which were used in the determination of the absorbing CO column densities, are also presented. The rotational structures of the K-X, L(prime)-X, and L-X bands do not overlap in the low-temperature spectra, allowing for the first unambiguous determination of these band oscillator strengths. We also report revised room temperature measurements of integrated cross sections for the K-X, L(prime)-X, and L-X bands, in which distortions in the measured spectra due to insufficient instrumental resolution have been minimized; the revised room temperature integrated cross sections are consistent with the low-temperature results.

Stark, G.↗
NASA NTRS1993

A multi-transition study of carbon monoxide in the Orion A molecular cloud. II - C(O-18)

We present an analysis of density, temperature, and excitation conditions in a one half square degree region around BN/KL in Orion A using new C(O-l8) J = 1 yields 0 and J = 2 yields 1 data. This paper extends a previous study of Orion A, based on a multitransition analysis of (C-13)O, to the optically thinner C(O-18) species that traces better the dense inner regions of giant molecular clouds. From the C(O-18) maps we identify several condensations and are able to derive their size, linewidth, average density, mass, and virial mass.

Dutrey, A.↗
NASA NTRS1994

High-resolution oscillator strength measurements for the A(v') - X(0) bands of carbon monoxide with 11 less than or equal to v' less than or equal to 14

Band oscillator strengths (f-values) for four bands of the Fourth Positive system (A (1)Pi - Chi(sup 1) Sigma(+)) of CO have been determined from high-resolution (lambda/Delta lambda approximately equal to 150,000) absorption spectra. The bands, (14, 0) through (11, 0), are at wavelengths between 121 and 127 nm. Our f-values for the (11, 0) and (12, 0) bands support those of Chan, Cooper, & Brion (1993), which have been shown to be consistent with observations of CO in the clouds in the line of sight to zeta Oph. Our f-values for the (13, 0) and (14, 0) bands are the first directly measured values for these bands.

Smith, Peter L.↗
NASA NTRS1995

High-resolution absorption cross section measurements of supersonic jet-cooled carbon monoxide between 92.5 and 97.4 nanometers

High-resolution photoabsorption cross sections for eight CO bands, at wavelengths between 92.5 nm and 97.4 nm, have been measured in a supersonic jet-cooled source (approximately equals 20 K) at the Photon Factory synchrotron radiation facility. New integrated cross sections are reported for four bands between 92.5 nm and 94.2 nm. A low-temperature spectrum of the W(1)-X(0) band (95.6 nm), which was used to determine the absorbing CO column densities, is also presented. Additional jet-cooled cross section measurements were made on the L(0)-X(0), K(0)-X(0), and W(0)-X(0) bands (96.7-97.4 nm) which verify previously published results. A self-consistent set of band oscillator strengths is presented for the eight bands studied.

Yoshino, K.↗
NASA NTRS1994

Solid carbon monoxide in the Serpens dark cloud

The 4.67 micrometer absorption feature of solid CO is an important signature of grain mantles in molecular clouds. This paper presents new observations of solid CO absorption in the spectra of four infrared sources in and behind the Serpens dark cloud. We also present supplementary 2.0-2.5 micrometer spectra which clarify the nature of selected sources. Solid CO profiles are compared with models based on laboratory data. In common with previous studies of other clouds, we find that the observed profiles are consistent with the presence of two distinct phases of CO-bearing ice, one dominated either by CO itself or by CO mixed with absorption relative to that of the water-ice feature at 3.1 micrometers is unusually high in Serpens: we deduce column densities for CO and H2O in solid form and conclude that the mean CO abundance in dust is 40% of the H2O abundance, compared with values in the range 0%-30% typical of other molecular clouds. On the basis of its 2.0-2.5 micrometer spectrum and near-infrared colors, we deduce the infrared source CK 2 to be a K5-M0 III field star situated behind the Serpens cloud and suffering 40-50 mag of visual extinction. Assuming empirical correlations between extinction and total (gas + dust) CO column density, we estimate the CO depletion (i.e., the fraction of interstellar CO in the line of sight tied up in grains) to be approximately 40% in the intracloud medium of the Serpens cloud, comparable with previous estimates for the Taurus dark cloud, and much higher than that found in the environments of protostellar objects.

Chiar, J. E.↗
NASA NTRS1994

Interstellar carbon monoxide toward zeta Ophiuchi

Interstellar CO A-X bands in the spectrum of zeta Oph were recorded at high Sound-to-Noise (S/N) with grating G160M of the Goddard High Resolution Spectrograph on the Hubble Space Telescope. Isotopic fractionation of CO is severe: CO-12/CO-13 = 167, C(16)O/C(18)O approximately equal to 1550 and C(16)O/C(17)O is greater than 5900 are found where C-12/C-13 = 70, O-16/O-18 = 500, and O-16.O-17 = 2600 are observed or expected. Standard models of the zeta Oph cloud predict CO-12/CO-13 is less than or approximately 70. The higher observed ratio suggests that photodissociation of CO, not the isotopic charge exchange reaction ((13)C(+) + CO reversible reaction (12)C(+) + (13)(CO), is the dominant influence on the CO-12/CO-13 ratio.

Lambert, David L.↗
NASA NTRS1994

Intersystem transitions of interstellar carbon monoxide toward zeta Ophiuchi

Absorption from seven intersystem (triplet-singlet) transitions of interstellar (12)CO were detected in ultraviolet spectra of zeta Oph. The observed equivalent widths are approximately consistent with the transitions' predicted f-values and the (12) CO column density derived from the weakest of the observed A-X bands. These unsaturated intersystem transitions provide the opportunity to measure the (12)CO column density for heavily reddened (dense) sight lines. Laboratory measurements of oscillator strengths more precise than available ones will be needed to derive accurate column densities.

Federman, S. R.↗
NASA NTRS1993

Latitudinal distribution of carbon monoxide in the deep atmosphere of Venus

A large number of i.r. spectra of Venus was obtained using the Near-Infrared Mapping Spectrometer (NIMS) on the Galileo spacecraft, during the February 1990 encounter. Preliminary results show an apparent increase in the tropospheric CO volume mixing ratio (vmr) in the northern polar region. Other possible explanations of the observations are examined and rejected and an increase of the CO abundance north of 47 deg N of (35 +/- 15)% is inferred. Some possible causes of this enhancement are suggested.

Collard, A. D.↗
NASA NTRS1994

Relationship of ozone and carbon monoxide over North America

Observations at sites in eastern North America show a strong correlation between O3 and CO concentrations in summer, with a consistent slope DeltaO3/DeltaCO approximately = 0.3. Observations in the aged Denver plume at Niwot Ridge, Colorado, also show a strong correlation but with DeltaO3/DeltaCO = 0.15. These data offer a sensitive test for evaluating the ability of photochemical models to simulate production of O3 over North America and its export to the global atmosphere. Application to the Harvard/Goddard Institute for Space Studies three-dimensional, continental-scale model shows that the model gives a good simulation of the observed O3-CO correlations and of the associated DeltaO3/DeltaCO. This successful simulation lends support to model estimates of 6 Gmol/d for the net O3 production in the U.S. boundary layer in summer (corresponding to a net O3 production efficiency of 5.5, which is the number of O3 molecules produced per molecule of NOx consumed) and 70% for the fraction of the net production that is exported to the global atmosphere. Export of U.S. pollution appears to make a significant contribution to total tropospheric O3 over the northern hemisphere in summer. Simple interpretation of observed DeltaO3/DeltaCO as an O3/CO anthropogenic enhancement ratio is shown to underestimate substantially anthropogenic O3 production, because O3 and CO concentrations are negatively correlated in the absence of photochemistry. It is also shown that concurrent observations of DeltaO3/DeltaCO and DeltaO3/Delta(NO(y)-NO(x)) ratios can be used to impose lower and upper limits on the net O3 production efficiency.

Chin, Mian↗
NASA NTRS1994

Global circulation, thermal structure, and carbon monoxide distribution in Venus' mesosphere in 1991

Millimeter-wave observations of CO lines have provided a detailed picture of Venus' mesosphere dynamics in 1991 from simultaneous measurements of absolute wind velocities in two layers and of temperature and CO horizontal and vertical profiles at 75-115 km. Venus' circulation at 90-110 km was characterized in 1991 by the superposition of a zonal retrograde flow and a subsolar-to-antisolar flow of approximately equal velocities, increasing from about 40 +/- 15 m/sec at 95 km to 90 +/- 15 m/sec at 105 km altitude. The magnitude of the increase of the SS-AS flow is consistent with Venus thermosphere general circulation models (VTGCM). At 105 km, the data further indicate a cos(latitude) dependence of the zonal flow and marginally suggest the presence of a poleward meridional component of 35 +/- 30 m/sec. No obvious day-to-day variations of the circulation are evident in the data at the 20 m/sec level. Thermal profiles in the low-latitude region appear to be consistent with the Pioneer Venus nightside profile, except above 110 km, where they are somewhat colder. High-latitude warming is still found, but mid-latitudes appear to be colder than the equator. The atmosphere appears to be in cyclostrophic balance up to about 105 km. The horizontal distribution of CO on Venus' nightside is essentially uniform, both in latitude and in local time. This behavior agrees with VTGCM simulations in which the zonal flow velocity is prescribed to match the observations. Comparison with previous wind measurements indicates that the zonal flow experiences dramatic long-term variations. This variability, along with short-term fluctuations of the mesospheric zonal flow (evidenced by the variability in the O2 nightglow emissions), apparently controls the CO and O2 nightglow distributions. Gravity wave activity is a plausible mechanism that can drive these variations.

Lellouch, Emmanuel↗
NASA NTRS1995

Quantum yield for carbon monoxide production in the 248 nm photodissociation of carbonyl sulfide (OCS)

Tunable diode laser absorption spectroscopy has been coupled with excimer laser flash photolysis to measure the quantum yield for CO production from 248 nm photodissociation of carbonyl sulfide (OCS) relative to the well-known quantum yield for CO production from 248 nm photolysis of phosgene (Cl2CO2). The temporal resolution of the experiments was sufficient to distinguish CO formed directly by photodissociation from that formed by subsequent S((sup 3)P(sub J)) reaction with OCS. Under the experimental conditions employed, CO formation via the fast S((sup 1)D(sub 2)) + OCS reaction was minimal. Measurements at 297K and total pressures from 4 to 100 Torr N2 + N2O show the CO yield to be greater than 0.95 and most likely unity. This result suggests that the contribution of OCS as a precursor to the lower stratospheric sulfate aerosol layer is somewhat larger than previously thought.

Zhao, Z.↗
NASA NTRS1997

Relative Band Oscillator Strengths for Carbon Monoxide: Alpha (1)Pi-Chi (1)Sigma(+) Transitions

Band oscillator strengths for CO transitions between the electronic states A (l)Pi and X(1)Sigma(+) were measured via absorption with a synchrotron radiation source. When referenced to the well-characterized (5,0) band oscillator strength, our relative values for the (7,0) to (11,0) bands are most consistent with the recent experiments of Chan et al. and the theoretical predictions of Kirby & Cooper. Since the results from various laboratory techniques and theory now agree, analyses of interstellar CO based on absorption from A-X bands are no longer hindered by uncertainties in oscillator strength.

Federman, S. R.↗