Study of Dissociative Electron Attachment and Ion-Pair Channels In H-/H2
Explore the source record for details and available documents.
Dissociative Electron Ion-Pair Channels↗
SEARCH · Search NASA
Results for “ion-pair”
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.
An investigation of the solar zenith angle variation of D-region ionization
Model calculations are carried out with a view to interpreting the solar zenith angle variation of D-region ionization. A model is developed for the neutral chemistry including the transport terms relating to molecular and eddy diffusion. The diurnal behavior is described of the minor neutral constituents formed in an oxygen-hydrogen-nitrogen atmosphere, in the height interval between 30 and 120 km. Computations carried out for two cases of the eddy diffusion coefficients models indicate that the constituents which are important for the D-region positive-ion chemistry do not show a significant variation with zenith angle for values up to 75 deg over the D-region heights. In the ion chemistry model, ion-pair production rates are calculated for solar X-rays between 1 A and 100 A, EUV radiations from 100 A up to the Lyman-alpha line, precipitating electrons, and galactic cosmic rays. The solar zenith angle variation of the positive-ion composition, negative-ion composition, and the electron densities are described up to 75 deg zenith angle, in the height interval between 60 and 100 km.
Ratnasiri, P. A. J.↗
Chemical analysis of LARC-160 polyimide
As part of a detailed NASA-sponsored study of chemical composition/property sensitivity of the LARC-160 polymerization of monomeric reactants (PMR) polyimide system, a number of liquid chromatographic techniques have been employed. The ester monomers in this system are characterized by a reverse-phase ion-suppression method. Mono, di, and triesters of the 3,3',4,4'-benzophenonetetracarboxylic acid ingredient are identified and their isomeric forms resolved. The 5-norbornene-2,3-dicarboxylic acid ester (nadic ester) endcapper is detected by low wavelength ultraviolet sensing. A second method, reverse-phase ion-pair chromatography, is employed for determining unreacted amines. The extent of resin B-staging is monitored through analysis of the ester/amine oligomers.
Dynes, P. J.↗
Solar flare ionization in the mesosphere observed by coherent-scatter radar
The coherent-scatter technique, as used with the Urbana radar, is able to measure relative changes in electron density at one altitude during the progress of a solar flare when that altitude contains a statistically steady turbulent layer. This work describes the analysis of Urbana coherent-scatter data from the times of 13 solar flares in the period from 1978 to 1983. Previous methods of measuring electron density changes in the D-region are summarized. Models of X-ray spectra, photoionization rates, and ion-recombination reaction schemes are reviewed. The coherent-scatter technique is briefly described, and a model is developed which relates changes in scattered power to changes in electron density. An analysis technique is developed using X-ray flux data from geostationary satellites and coherent scatter data from the Urbana radar which empirically distinguishes between proposed D-region ion-chemical schemes, and estimates the nonflare ion-pair production rate.
Parker, J. W.↗
An analysis at mesospheric coherent-scatter power enhancements during solar flare events
Solar flares produce increases in coherent-scatter power from the mesosphere due to the increase in free electrons produced by X-ray photoionization. Thirteen such power enhancements were observed at Urbana. When such an enhancement occurs at an altitude containing a turbulence layer with constant strength, the relative enhancement of electon density is estimated from the enhancement in power. Such estimates of enchanced electron density are compared with estimates of the X-ray photoionization at that altitude, deduced from geostationary satellite measurements. It is found that possible types ion-chemical reaction scheme may be distinguished, and the nonflare ion-pair production function may be estimated. The type of ion-chemical scheme and the nonflare ion-production function are shown to depend on the solar zenith angle.
Parker, J.↗
Non-enzymatic synthesis of the coenzymes, uridine diphosphate glucose and cytidine diphosphate choline, and other phosphorylated metabolic intermediates
Using urea and cyanamide, the two condensing agents considered to have been present on the primitive earth, uridine diphosphate glucose (UDPG), cytidine diphosphate choline (CDP-choline), glucose-1-phosphate (G1P), and glucose-6-phosphate (G6P) were synthesized under simulated prebiotic conditions. The reaction products were separated and identified using paper chromatography, thin layer chromatography, enzymatic analyses, and ion-pair reverse-phase high performance liquid chromatography. The possibility of nonenzymatic synthesis of metabolic intermediates on the primitive earth from simple precursors was thus demonstrated.
Mar, A.↗
Residual infrared absorption in Ti:Al2O3 crystals
The performance of Ti:Al2O3 lasers is impaired generally by an infrared absorption that occurs in the laser output wavelength region. On the basis of data for as-grown and annealed samples cut from Ti:Al2O3 crystals grown by the vertical-gradient-freeze (VGF) technique, we previously proposed that the residual absorption is due to Ti(3+) to Ti(4+) pairs. In this report, we present additional data that confirm this ion-pair model for the residual absorption, which can be attributed to excitation of the 3d electron of the Ti(3+) ion perturbed by the Coulomb field of the neighboring Ti(4+) ion and/or an associated Al vacancy.
Source record↗
Total Electron-Impact Ionization Cross-Sections of CFx and NFx (x = 1 - 3)
The discrepancy between experimental and theoretical total electron-impact ionization cross sections for a group of fluorides, CFx, and NFx, (x = 1 - 3), is attributed to the inadequacies in previous theoretical models. Cross-sections calculated using a recently developed siBED (simulation Binary-Encounter-Dipole) model that takes into account the shielding of the long-range dipole potential between the scattering electron and target are in agreement with experimentation. The present study also carefully reanalyzed the previously reported experimental data to account for the possibility of incomplete collection of fragment ions and the presence of ion-pair formation channels. For NF3, our experimental and theoretical cross-sections compare well with the total ionization cross-sections recently reported by Haaland et al. in the region below dication formation.
Huo, Winifred M.↗