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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

mm-wave observations of stratospheric HCN at tropical latitudes

Middle and upper stratospheric HCN has been measured using ground-based mm-wave emission spectroscopy during a series of observations made in Mauna Kea, HI, in June 1986. A volume mixing ratio of 190 + or - 40 pptv at about 40 km, and a decrease of concentration with altitude that is considerably slower than that predicted by current models are found. This could be an indication of an atmospheric source of HCN as yet unidentified.

Jaramillo, M.↗
NASA NTRS1990

Hydrogen constituents of the mesosphere inferred from positive ions - H2O, CH4, H2CO, H2O2, and HCN

The concentrations in the mesosphere of H2O, CH4, H2CO, H2O2, and HCN were inferred from data on positive ion compositions, obtained from one mid-latitude and four high-latitude rocket flights. The inferred concentrations were found to agree only partially with the ground-based microwave measurements and/or model prediction by Garcia and Solomon (1985). The CH4 concentration was found to vary between 70 and 4 ppb in daytime and 900 and 100 ppbv at night, respectively. Unexpectedly high H2CO concentrations were obtained, with H2CO/H2O ratios between 0.0006 and 0.1, and a mean HCN volume mixing ratio of 6 x 10 to the -10th was inferred.

Kopp, E.↗
NASA NTRS1992

Millimeter-wave observations of Saturn, Uranus, and Neptune - CO and HCN on Neptune

Saturn, Uranus, and Neptune were observed at millimeter wavelengths with the IRAM 30 m telescope. The major result is the detection of CO and HCN in Neptune's stratosphere, with respective mixing ratios of (6.5 +/- 3.5) x 10 exp -7 and (3 +/- 1.5) x 10 exp -10. CO seems to be present in Neptune's troposphere as well and to slowly decrease with altitude (scale height about 200 km). HCN is probably formed from reactions between CH3 and N, which can be supplied in sufficient amounts by escape from Triton's atmosphere. The origin of CO, however, is more problematic, because: (1) thermochemical models fail to reproduce the observed abundance by a factor of about 1000; and (2) an external source would require a very large flux of oxygen. CO appears to be at least 15 times less abundant on Uranus than on Neptune. Finally, an upper limit of 10 exp -7 for CO in Saturn's stratosphere suggests an internal origin for Saturnian CO.

Rosenqvist, Jan↗
NASA NTRS1996

Trends of OCS, HCN, SF6, CHClF2 (HCFC-22) in the Lower Stratosphere from 1985 and 1994 Atmospheric Trace Molecule Spectroscopy Experiment Measurements Near 30 deg. North Latitude

Volume mixing ratio (VMR) profiles of OCS, HCN, SF6, and CHClF2 (HCFC-22) have been measured near 30 deg N latitude by the Atmospheric Trace Molecule Spectroscopy Fourier transform spectrometer during shuttle flights on 29 April - 6 May 1985 and 3-2 November 1994. The change in the concentration of each molecule in the lower stratosphere has been derived for this 9 1/2-year period by comparing measurements between potential temperatures of 395 to 800 K (approximately 17 to 30 km altitude) relative to simultaneously measured values of the long-lived tracer N2O. Exponential rates of increase inferred for 1985-to 1994 from these comparisons are (0.1 plus or minus 0.4)% yr(exp-1) for OCS, (1.0 plus or minus 1.0)% yr(exp-1) for HCN, (8.0 +/- 0.7)% yr(exp-1) for SF6, and (8.0 +/- 1.0)% yr(exp-1) for CHClF2 (HCFC-22), 1 sigma. The lack of an appreciable trend for OCS suggests the background (i.e. nonvolcanic) source of stratospheric aerosol was the same during the two periods. These results are compared with trends reported in the literature.

Rinsland, C. P.↗
NASA NTRS1996

Haze Formation is an Important Sink for HCN on Titan

Titan's organic haze is potentially an important sink of photochemically produced carbon and nitrogen compounds. An assortment of microphysical haze models all suggest that the haze production rate is 10(exp -14) gm per square centimeter per second, within a factor of two. Spectral analysis of laboratory tholins compared to Titan's geometric albedo spectrum suggest that the laboratory material is a good analog to Titan's haze. The laboratory material has an elemental composition given approximately by C4H4N, with an uncertainty in the C/N ratio of a factor of two. Thus, the haze represents a sink for C of 4 x 10(exp 8) per square centimeter per second, and a sink for N of 1 x 10(exp 8) per square centimeter per second. The C sink is small compared to condensation of hydrocarbons but the sink for N is comparable to the total production rate of HCN. Because estimates of the eddy diffusion profile on Titan have been based on the HCN profile, inclusion of this additional sink for N will affect estimates for all transport processes in Titan's atmosphere.

McKay, Christopher P.↗
NASA NTRS2004

A SIFT ion-molecule study of some reactions in Titan's atmosphere. reactions of N(+), N(2)(+), and HCN(+) with CH(4), C(2)H(2), and C(2)H(4)

The results of a study of the ion-molecule reactions of N(+), N(2)(+), and HCN(+) with methane, acetylene, and ethylene are reported. These studies were performed using the FA-SIFT at the University of Canterbury. The reactions studied here are important to understanding the ion chemistry in Titan's atmosphere. N(+) and N(2)(+) are the primary ions formed by photo-ionization and electron impact in Titan's ionosphere and drive Titan's ion chemistry. It is therefore very important to know how these ions react with the principal trace neutral species in Titan's atmosphere: Methane, acetylene, and ethylene. While these reactions have been studied before the product channels have been difficult to define as several potential isobaric products make a definitive answer difficult. Mass overlap causes difficulties in making unambiguous species assignments in these systems. Two discriminators have been used in this study to resolve the mass overlap problem. They are deuterium labeling and also the differences in reactivities of each isobar with various neutral reactants. Several differences have been found from the products in previous work. The HCN(+) ion is important in both Titan's atmosphere and in the laboratory.

Extraterrestrial Environment/chemistry↗
NASA NTRS2016

A41a-0017: Using TES Retrievals of HCN to Determine Fire Influence of Aura-TES Footprints

Hydrogen cyanide (HCN) has successfully been used as a tracer of biomassburning in the context of aircraft campaigns. We show HCN observations fromAura-TES for a major fire in Indonesia in 2006, and globally over differentseasons. We develop a fire-influence flag for TES observations and show howthis relates to enhancements of other TES products, such as PAN, carbonmonoxide, and ozone.

ozone↗
NASA NTRS1970

Plasma refractive effects in HCN lasers

Plasma refractive index effects in pulsed HCN lasers, calculating stable cavity mirror curvatures constriction as function of electron density by ray matrix approach

Mccaul, B. W.↗
NASA NTRS1974

Chemical evolution. XXI - The amino acids released on hydrolysis of HCN oligomers

Major amino acids released by hydrolysis of acidic and basic HCN oligomers are identified by chromatography as Gly, Asp, and diaminosuccinic acid. Smaller amounts of Ala, Ile and alpha-aminoisobutyric acid are also detected. The amino acids released did not change appreciably when the hydrolysis medium was changed from neutral to acidic or basic. The presence of both meso and d, l-diaminosuccinic acids was established by paper chromatography and on an amino acid analyzer.

Ferris, J. P.↗
NASA NTRS1974

Rotational excitation of HCN by collisions

Rate constants for the rotational excitation of HCN by collisions with He atoms at temperatures below 100 K were computed from first principles and are presented in tabular form. The potential energy surface was obtained by using the uniform electron gas model of Gordon and Kim (1972) and then joined smoothly to the asymptotic long-range perturbation theory potential valid at large separations. Quantum close-coupling theory was used to analyze the collision dynamics. Individual rates are believed to be accurate to within 50% above 30 K and within a factor of two below 20 K. The results should be extendable to excitation by collision with H2 and may therefore be of value in the study of interstellar clouds.

Green, S.↗
NASA NTRS1977

On the relationship of interstellar N2H/+/, HCO/+/, HCN, and CN

A survey of 73 sources has been made in the emission lines of N2H(+) and HCO(+), including detailed maps of four sources (Ori A, OMC-2, DR 21 OH, and NGC 6334). These data are combined with equally extensive data for HCN and CN to make a detailed study of the spatial relationship of these four species. Actual abundance ratios are shown to vary, often sharply, over small scale lengths (of the order of 1 arcmin) within the mapped sources. Excitation temperatures also vary. All four species appear to be subthermally excited. The abundance ratios and their spatial variations are interpreted in terms of ion-molecular formation and destruction processes. It is concluded that the relative abundances of CO may be considerably lower in some regions than previously believed. No evidence is found for variations in the C/O ratio over small scale lengths in Ori A. The degree of ionization of the Ori A molecular cloud may be significantly different from that of other molecular clouds.

Turner, B. E.↗
NASA NTRS1977

Electron-impact excitation of the low-lying electronic states of HCN

The first study of the low-energy electron-impact excitation of low-lying electronic transitions in the HCN molecule is reported. Measurements were made at incident electron energies of 11.6 and 21.6 eV in the energy-loss range of 3-10 eV, and at scattering angles of 20-130 deg. Inelastic scattering spectra were placed on the absolute cross-section scale by determining first the ratio of inelastic-to-elastic scattering cross sections, and then separately measuring the absolute elastic scattering cross section. Several new electronic transitions are observed which are intrinsically overlapped in the molecule itself. Assignments of these electronic transitions are suggested. These assignments are based on present spectroscopic and cross-sections measurements, high-energy electron scattering spectra, optical absorption spectra, and ab initio molecular orbital calculations.

Chutjian, A.↗
NASA NTRS1982

Ab initio calculation of infrared intensities for the linear isoelectronic series HCN, HNC, CO, HCO/+/, and HOC/+/

Ab initio infrared intensities and dipole moment derivatives expressed in atomic polar tensor form are calculated using the 4-31 and 6-31G(double asterisk) basis sets for the isoelectronic HCN, HNC, CO, HCO(+), and HOC(+) series of molecules. The calculated atomic polar tensors are analyzed in terms of the charge-charge flux-overlap model, which is found to be useful in explaining some of the trends observed in the dipole moment derivatives for this series of molecules. A detailed examination of the dipole moment derivatives for the structural isomers indicates some of the ways in which experimental atomic polar tensors for one isomer should be modified to predict infrared intensities for the other isomer. The absolute intensities calculated for the HCO(+) and HOC(+) ions are believed to be accurate to within a factor of 2 and thus should be useful in astrophysical applications.

Rogers, J. D.↗
NASA NTRS1986

Ion-molecule reactions of hydrocarbon ions in C2H2 and HCN

Rate coefficients and product distributions have been determined for reaction of the ions C(x)H(y)+ (x ranging from 1 to 4, and y ranging from 0 to 4) with C2H2 and HCN. The measurements were obtained using the ion cyclotron resonance technique at 298 K. In several reactions an association product was observed at pressures as low as 0.000001 torr, and in these cases stabilization of the intermediate was assumed to be by photon emission. Most of the reaction studied yield ions having a larger carbon skeleton than the reactant ion. These reactions provide routes for building large organic and organonitrogen molecules in combustion zones of unsaturated hydrocarbon flames and in astrochemical environments.

Anicich, V. G.↗
NASA NTRS1987

HCN and chromophore formation on Jupiter

Reaction paths for the formation of HCN and chromophores on Jupiter are suggested. The reactions involve photolysis of ammonia/acetylene mixtures. Experimental data supporting these pathways are reported.

Ferris, James P.↗
NASA NTRS1990

Absorption intensities and complex refractive indices of crystalline HCN, HC3N, and C4N2 in the infrared region

IR absorption intensities are presented for thin crystalline films of HCN, HC3N, and C4N2, together with n and k complex refractive indices determined on the basis of an iterative program for the Kramers-Konig integral via a least-squares, point-by-point fitting of the experimental transmission data. It is established that the transmission spectra generated by means of these n and k values can reproduce the experimental transmission observation values to within + or - 2 percent.

Masterson, C. M.↗
NASA NTRS1991

Laser stark spectroscopy of SO2 with the HCN laser

The far infrared laser Stark spectrum of SO2 was investigated using the 337-micron line of the HCN laser. Two distinct families, one originating at low field and the other at high field, were observed. The high field transition is identified. A significant fourth-order Stark shift was observed for this transition in the presence of a large second-order Stark shift. The zero-field frequency of the assigned transition was obtained by accounting for the fourth-order contribution.

Sarker, J. C.↗