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At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Aminonitriles - Possible role in chemical evolution

The formation of HCN, ammonium cyanide, alkylnitriles, aminoacetonitrile and its C- and N-methyl homologs was demonstrated earlier in a simulated Jovian atmosphere. The polymeric material resulting in these experiments was shown to give glycine, alanine, sarcosine, aspartic acid and some imino dibasic acids on acid hydrolysis, suggesting thereby the participation of the monomeric nitriles in the formation of the polymeric product(s). Further examination of products resulting from semicorona and arc discharge through a mixture of methane and ammonia has provided evidence for the formation of alkylaminopropionitriles as a complex mixture and also some pyridyl and pyrimidyl type heterocyclic compounds. A gas chromatograph/mass spectrometer examination of the heterocyclics showed resemblance with those found in some carbonaceous chondrites. The significance of these findings in relation to chemical evolution is discussed.

Chadha, M. S.↗
NASA NTRS1974

Molecule searches in Comet Kohoutek /1973f/ at microwave frequencies

Nine transitions of the possible parent molecules H2O, NH3, CH3OH and N2O as well as the OH radical were searched for in Comet Kohoutek (1973f) in the frequency range 22.2-25.2 GHz. These molecules were not detected, but the upper limits for the optical depth, mean column density and the production rate are derived for each of the molecules. These results are discussed and compared with the reported detections of HCN and CH3CN emission and OH absorption.

Mango, S. A.↗
NASA NTRS1975

Comment on the accuracy of Rabitz' effective potential approximation for rotational excitation by collisions

Cross sections for rotational excitation of HCN by low-energy collisions with He have been computed with the effective-potential approximation of Rabitz (1972) and compared with accurate quantum close-coupling results. Elastic cross sections are found to agree to about 20%; inelastic cross sections agree in general magnitude, but not in detailed values for specific quantum transitions.

Green, S.↗
NASA NTRS1975

Observations of 1-millimeter continuum radiation from the DR 21 region

Continuum emission at 1 mm has been mapped with 1-min resolution over a 3-min by 8-min area including the compact H II region DR 21, the maser source W75(S)-OH, and the central portions of the surrounding molecular cloud. Peaks in the 1-mm intensity are observed at the positions of DR 21 and W75(S)-OH, and are roughly coincident with less marked peaks in the intensity of HCN and CO emission. An extended component of 1-mm emission is present as well. The principal source of 1-mm radiation is thought to be thermal emission from dust within the molecular gas. The characteristics of this radiation which make it a promising tool for the study of molecular clouds are briefly discussed.

Werner, M. W.↗
NASA NTRS1975

Semiconducting polymers for gas detection

Conjugated polyenes, and polyesters containing phthalocyanine in their backbone, were synthesized. These polymers were characterized by chemical analysis, thermogravimetric analysis, spectral analysis, and X-ray diffraction studies for crystallinity, as well as for their film-forming capability and gas/polymer interactions. Most of the polymers were relatively insensitive to water vapor up to 50 percent relative humidity, but the polyester/phthalocyanine (iron) polymer was relatively insensitive up to 100 percent RH. On the other hand, poly(p-dimethylaminophenylacetylene) was too conductive at 100 percent RH. Of the gases tested, the only ones that gave any evidence of interacting with the polymers were SO2, NOx, HCN and NH3. Poly(imidazole)/thiophene responded to each of these gases at all relative humidities, while the other polymers gave varying response, depending upon the RH. Thus, since most of these gases were electron-accepting, the electron-donating character of poly(imidazole)/thiophene substantiates the concept of electronegativity being the operating principle for interaction effects. Of the six polymers prepared, poly(imidazole)/thiophene first showed a very good response to smoldering cotton, but it later became nonresponsive; presumably due to oxidation effects.

Byrd, N. R.↗
NASA NTRS1976

Radio detections of cometary molecular transitions: A review

Radio detections of CH, OH, HCN, CH3CN, and several unidentified species in comet Kohoutek and the detection of H2O emission from comet Bradfield are discussed in terms of the similarities and differences between cometary molecules and interstellar molecules. Emphasis is placed on excitation and chemistry. The observed projected densities and resulting gas production rates are considered along with the feasibility of future radio molecular observations of comets.

Snyder, L. E.↗
NASA NTRS1976

H2CO emission at 2 millimeters in dark clouds

The paper reports the detection of the 2-mm emission line due to the 2(12)-1(11) transition of H2CO at two positions in the Taurus dark cloud and one position in the dark cloud L134 N. The profiles of the observed emissions are plotted, and peak radiation temperatures at 2 mm are determined for the three positions. These radiation temperatures are used along with data on the 2-mm H2CO absorption line and computed cross sections for H2-H2CO collisions to deduce the molecular hydrogen density and the ortho-H2CO column density in the two clouds. The results are shown to support previous theoretical estimates of the H2CO/H2 and the H2(C-12)O/H2(C-13)O ratios. It is concluded that if the abundances of CS and HCN in the clouds are equal to that of H2CO, emissions from these molecules should be easily detectable.

Evans, N. J., II↗
NASA NTRS1976

On the accuracy of the 'decoupled l-dominant' approximation for atom-molecule scattering

Cross sections for rotational excitation and spectral pressure broadening of HD, HCl, CO, and HCN due to collisions with low energy He atoms have been computed within the 'decoupled l-dominant' (DLD) approximation and are compared with accurate close coupling results and also with two similar approximations, the effective potential of Rabitz and the coupled states of McGuire and Kouri. DLD predictions of state-to-state cross sections are rather good, being only slightly less accurate than coupled states results. DLD is far superior to either the coupled states or effective potential methods for pressure broadening calculations, although it may not be uniformly of the quantitative accuracy desirable for obtaining intermolecular potentials from experimental data.

Green, S.↗
NASA NTRS1975

Reactions of aminomalononitrile with electrophiles

Aminomalononitrile (HCN trimer) reacts with electrophiles such as aldehydes and acrylonitrile under very mild conditions of temperature and pH to produce intermediates which, after acid hydrolysis, yield amino acids. The following amino acids have been identified and quantitated: glycine, D,L-erythro- and D,L-threo-beta-hydroxyaspartic acids, D,L glutamic acid, and D,L-threonine and allo-threonine. The mechanism of their formation and the possible significance of these reactions in prebiotic syntheses are discussed.

Thanassi, J. W.↗
NASA NTRS1976

Microwave line transitions in the 3-mm wavelength range in comet Kohoutek /1973f/

A search program for microwave line transitions in comet Kohoutek is reviewed. Observations in the 3-mm wavelength region were carried out before perihelion from December 15 to 20, 1973, and after perihelion from January 3 to 7, 1974. During these times, the comet was between 0.3 and 0.5 AU from the sun. Gas production rates of HCN are several times 10 to the 27th power to about 10 to the 28th power molecules/sec at approximately 0.4 AU. Upper limits for CH3CN and several other molecules are given.

Huebner, W. F.↗
NASA NTRS1976

Ion cyclotron resonance studies of some reactions of C/+/ ions

Product distributions and rate constants for the reaction of ground state C(+) ions with O2, NO, HCl, CO2, H2S, H2O, HCN, NH3, CH4, H2CO, CH3OH, and CH3NH2 have been measured. Rate constants were obtained using ion cyclotron resonance trapped ion methods, and product distributions were obtained using a tandem mass spectrometer. Rapid carbon isotope exchange has also been observed in C(+)-CO collisions.

Anicich, V. G.↗
NASA NTRS1977

Computational tests of angular momentum decoupling approximations for pressure broadening cross sections

The utility of several approximate scattering methods for predicting collision induced spectral pressure broadening has been tested by comparison with accurate close coupling results. In particular, broadening of the pure rotational spectra of HD, HCl, CO, and HCN - all perturbed by low energy collisions with He atoms - has been computed using the effective potential formalism of Rabitz, the decoupled l-dominant approximation of DePristo and Alexander, and the j(2)-conserving coupled states method of McGuire and Kouri. For this last method, pressure broadening cross sections have been obtained with the new, correct expression recently derived by Goldflam and Kouri as well as with an earlier formalism based on an incorrect labeling of the scattering matrices. These methods were found to be generally diasppointing for predicting pressure broadening with the exception of the new, correctly formulated j(2)-conserving coupled states method which was found to agree quantitatively (better than 5%) with close coupling values for all cases studied.

Green, S.↗
NASA NTRS1977

Isothermal degradation of poly-2,2'-/m-phenylene/-5,5'-bibenzimidazole

The isothermal degradation of poly-2,2'-(m-phenylene)-5,5'-bibenzimidazole in vacuo has been studied. Measurement of the increase in pressure with time, coupled with infrared analysis, was used to determine the distribution of the degradation products. Processes A and B with different second-order rate laws were determined to be significant in the temperature range of 550-700 C. Process A leads to the formation of equimolar quantities of hydrogen and ammonia and has an activation energy of 68 kcal/mole. Process B leads to the production of HCN, NH3, and H2 in the ratio of 1:1:2.5 and has an activation energy of 77 kcal/mole. The activation energies and the rate laws are consistent with a mechanism in which the initial degradation step is the bimolecular reaction of two aromatic rings.

Lerner, N. R.↗
NASA NTRS1977

Observation of J = 1-0 emission from H/N-15/C

Emission from the J = 1-0 transition of H(N-15)C has been detected in the direction of DR21(OH). The transition frequency of 88,865.69 MHz was measured in the laboratory by microwave absorption spectroscopy. The computed N-15/C-13 isotopic abundance ratio of 1.01 for DR21(OH) is larger than those calculated from isotopes of HCN in other interstellar clouds, perhaps implying a localized enrichment in N-15 in DR21(OH).

Brown, R. D.↗
NASA NTRS1978

The energetics of molecular clouds. II - The S140 molecular cloud

Techniques of analysis which allow estimates of kinetic temperature, gas density, gas cooling rate, and dust cooling rate are applied to the S140 molecular cloud. Maps of this cloud in various molecular lines are examined which reveal the existence of a strong temperature and density peak near the H-alpha rim and the presence of a strong near-IR source very near that peak. This source is found to have an energy distribution which is very similar to that of the Becklin-Neugebauer object, including the silicate feature at 9.5 microns. The heating and cooling rates for the gas and dust in S140 are estimated, and the predicted cooling rate for dust is shown to be much greater than that for gas. The molecular-line observations are compared with a spherical large-velocity-gradient trapping calculation. An optimum cloud model is developed which indicates that: (1) (C-13)O, HCO(+), and H2CO are about 10 times less abundant in S140 than in dark clouds; (2) the HCN abundance is approximately 4 times the H2CO abundance in S140, compared with roughly equal values in dark clouds; and (3) the (C-13)O/C(O-18) ratio is consistent with terrestrial isotope ratios.

Blair, G. N.↗
NASA NTRS1978

A new channel for the formation of hydrogen cyanide in CH2-N2 systems

The reaction between N2 and either the singlet or the triplet electronic state of CH2 is investigated in order to shed light on the formation of NO in fuel-rich hydrocarbon flames. For the reaction of N2 and the triplet CH2, a rate constant less than or equal to 10 to the minus 16th power cu cm/molecule-sec is obtained. The time history of hydrogen cyanide production from the CH2-N2 systems is discussed as a basis for understanding the possible reaction routes from HCN to NO.

Laufer, A. H.↗
NASA NTRS1978

Upper limits to trace constituents in Jupiter's atmosphere from an analysis of its 5 micrometer spectrum

A high-resolution spectrum of Jupiter at 5 micrometers recorded at the Kuiper Airborne Observatory is used to determine upper limits to the column density of 19 molecules. The upper limits to the mixing ratios of SiH4, H2S, HCN, and simple hydrocarbons are discussed with respect to current models of Jupiter's atmosphere. These upper limits are compared to expectations based upon the solar abundance of the elements. This analysis permits upper limit measurements (SiH4), or actual detections (GeH4) of molecules with mixing ratios with hydrogen as low as 10 to the minus 9th power. In future observations at 5 micrometers the sensitivity of remote spectroscopic analyses should permit the study of constituents with mixing ratios as low as 10 to the minus 10th power, which would include the hydrides of such elements as Sn and As as well as numerous organic molecules.

Treffers, R. R.↗
NASA NTRS1978

Nonequilibrium chemistry in shocked molecular clouds

The gas-phase chemistry is studied behind a 10-km/s shock propagating into a dense molecular cloud. The principal conclusions are that: the concentrations of certain molecules (CO, NH3, HCN, N2) are unperturbed by the shock; other molecules (H2CO, CN, HCO(+)) are greatly decreased in abundance; and substantial amounts of H2O, HCO, and CH4 are produced. Approximately 1 million yr (independent of the density) must elapse after shock passage before chemical equilibrium is attained.

Iglesias, E. R.↗