The atmosphere of the hydrogen-deficient star sigma Orionis E
Sigma Orionis E hydrogen-deficient atmosphere, using grid of constant-flux model atmospheres to determine abundances of five elements
Bless, R. C.↗
SEARCH · Search NASA
Results for “Sigma S”
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.
Mid-latitude rocket observations of the altitude profile of the O2 /a /1 Delta g//-/X /3 Sigma g plus// transition
Nike-Apache rocket carrying radiometer for detection of O2 /a /1 Delta g//-/X /3 Sigma g plus// transition
Jones, W. H.↗
Deactivation of N2A 3 Sigma u plus molecules in the aurora
Analysis of N2A 3 Sigma u positive molecule deactivation in auroras using atmospheric model based on mass spectrometer measurements
Shemansky, D. E.↗
Excitation of the metastable E(3 Sigma g plus) state of N2 by electron impact
The contribution of the N2(E(3 Sigma g plus)) state to the total metastable excitation function of N2 assessed on the basis of time-of-flight studies of metastable nitrogen molecules. The cross section for electron impact excitation state was determined in the domain of the resonance form threshold (11.87 eV) to an energy of about 13 eV. The maximum value of the cross section was found to be (7.0 + or - 4.0) x 10 to the -18th power sq cm at an energy of 12.2 eV. The measurement was made absolute by using the previously determined yield of the metastable detector, the lifetime of the E state, and by eliminating the energy spread in the electron beam from the raw data. The half-width (FWHM) of the resonance-like excitation function near threshold was found to be about 0.4 eV. No substantial evidence was obtained from the present data for the presence of the nonresonant part of the excitation function for the state studied.
Borst, W. L.↗
Spectrocopic measurements of water vapor plasmas at high resolution: The optical transition probabilities for OH (A 2 Sigma - X 2 Pi)
Emission and absorption spectra of water vapor plasmas generated in a wall-stabilized arc at atmospheric pressure and 4 current, and at 0.03 atm and 15 to 50 A, were measured at high spatial and spectral resolution. The gas temperature was determined from the shape of Doppler-broadened rotational lines of OH. The observed nonequilibrium population distributions over the energy levels of atoms are interpreted in terms of a theoretical state model for diffusion-controlled arc plasmas. Excellent correlation is achieved between measured and predicted occupation of hydrogen energy levels. It is shown that the population distribution over the nonpredissociating rotational-vibrational levels of the A 2 Sigma state of OH is close to an equilibrium distribution at the gas temperature, although the total density of this state is much higher than its equilibrium density. The reduced intensities of the rotational lines originating in these levels yielded Boltzmann plots that were strictly linear.
Klein, L.↗
Vibrational population of the A super 3 sigma sub u/+/ and B super 3 pi sub g states of N2 in normal auroras.
Use of new electron impact excitation cross sections for the six lowest triplet states (A, B, W, C, E, D) of N2, and solution of the coupled equations of statistical equilibrium to obtain the vibrational population of each electronic state. The results show that cascade from high levels of the A super 3 sigma sub u(+) state and from the W super 3 delta sub u state is significant in populating the lower vibrational levels of the B state and hence the character of its ?apparent' excitation cross sections. For the B state excited under auroral conditions, the fraction of the total population due to cascade processes exceeds 25% for all levels lower than 7 and is greater than 80% for B(v' = 0). For the A state under similar conditions, cascade from the B state contributes 50% or more of the total vibrational population for levels lower than 7, and 80% or more for levels below 4. For levels of the A state greater than 7, the A yields B transitions depopulate the levels rapidly and indicate that the Vegard-Kaplan emissions from these higher levels will be weak or totally absent in normal auroras.
Cartwright, D. C.↗
Oscillator strengths for the X/1 Sigma+/ - A/1 Pi/ system of CH+.
Oscillator strengths for the X/1 Sigma+/ - A/1 Pi/ system of CH+ computed to an estimated accuracy of 10 percent from ab initio wave functions are presented. These oscillator strength values are given for the two strongest interstellar lines of 4232 and 3957 A.
Yoshimine, M.↗
Eutectic superalloys strengthened by sigma, Ni3CB lamellae and gamma prime, Ni3Al precipitates
By means of a screening and solidification optimization study of certain alloys located on the gamma-sigma liquidus surface within the Ni-Cb-Cr-Al system, alloys with high temperature properties superior to those of all known superalloys were defined. One alloy, Ni - 19.7w/o Cb - 6.0w/o Cr - 2.5w/o Al, directionally solidified at 3 cm/hr met or exceeded each program goal. A second alloy, Ni-21.75 w/o Cb-2.55 w/o Al, although deficient in its inherent oxidation resistance, met the other program goals and combined a remarkable insensitivity of composite microstructure to solidification parameters with excellent low temperature toughness. This investigation demonstrated that useful properties for gas turbine airfoil application have been achieved by reinforcing a strong and tough gamma solid solution matrix containing precipitated gamma prime by a lamellar intermetallic compound Ni3 Cb having greater strength at elevated temperature.
Lemkey, F. D.↗
Automated system for measurement, collection and processing of hydrometeorological data aboard scientific research vessels of the GUGMS (SIGMA-s)
A report is made on the automated system known as SIGMA-s for the measurement, collection, and processing of hydrometeorological data aboard scientific research vessels of the Hydrometeorological Service. The various components of the system and the interfacing between them are described, as well as the projects that the system is equipped to handle.
Borisenkov, Y. P.↗
Software for the SIGMA-s
The software needed for the SIGMA-s is described. Various mathematical procedures, such as introducing corrections and parameters, interpolating for depth and altitude, isolating special points and layers in the distribution of hydrometeorological elements, smoothing of signals from sensors, critical analysis of and setting up the results in graphs and tables, coding of the data into information carriers, and recording of the data, are presented.
Dyubkin, I. A.↗
Vibrational structure in the photo-electron spectrum of O2+2Sigma(g)-(sigmag2s)
Discrete vibrational structure has been observed in the photo-electron spectrum of oxygen at an ionization potential of 40.33 eV. Two levels, attributed to the 02(+) 2 sigma g- final state, have been detected with a vibrational spacing of 0.071 eV.
Gardner, J. L.↗
MODC2 procedures for assembly of MODCOMP-2 programs using the Sigma 5 assembler
A set of programs was written to enable the METASYMBOL macro-assembler of the Sigma 5 to assemble programs for an attached MODCOMP-2 minicomputer. This program set is a follow-on to previously developed program sets which facilitated assemblies for the PDP-11 and SDS-930.
Layland, J. W.↗
Theoretical study of H/+/2 spectroscopic properties. IV - Adiabatic effects for the 2p pi sub u and 3d sigma sub g electronic states
Adiabatic corrections to the potential curves for the 2p pi sub u and 3d sigma sub g states of H(+)2 are reported. The effects of these corrections in altering spectroscopic properties of H(+)2 are described in some detail; likely consequences are indicated in two astrophysical applications.
Bishop, D. M.↗
CO/d-3 Delta sub i to X-1 Sigma +/ fluorescence from photodissociation of CO2 by 923 A photons
Measurements of vacuum ultraviolet fluorescence from the photodissociation of CO2 by photons from a N IV line emission source at a wavelength of 923 A have revealed a second CO band system in addition to the expected emission bands. Spectra with time resolution were obtained and the fluorescence lifetime and the dependence of fluorescence intensity on CO2 pressure were measured. An analysis of this data has permitted the second band system to be identified as originating from CO(d-3 Delta sub i to X-1 Sigma +) transitions.
Phillips, E.↗
A shock-tube determination of the SiO /A 1 Pi - X 1 Sigma +/ transition moment
The sum of the squares of the electronic transition moments for the A 1 Pi - X 1 Sigma + band system of SiO has been determined from absorption measurements conducted in the reflected-shock region of a shock tube. The test gas was produced by shock-heating a mixture of N2O, SiCl4, and Ar, and the spectra were recorded photographically in the 260-290-nm wavelength range. The values of the sum as a function of internuclear distance between 2.8 and 3.3 Bohr were determined by comparing the measured absorption spectrum with that produced by a line-by-line synthetic-spectrum calculation which accounted for instrumental broadening. The value of the sum so deduced at an internuclear distance of 3.0 Bohr was 1.0 + or - 0.3 atomic units.
Park, C.↗
Standalone engine simulator (SAES), Engine Dynamics simulator (EDS) Xerox Sigma 5 interface hardware manual
The ESS-EDS and EDS-Sigma interfaces within the standalone engine simulator are described. The operation of these interfaces, including the definition and use of special function signals and data flow paths within them during data transfers, is presented along with detailed schematics and circuit layouts of the described equipment.
Kirshten, P. M.↗
An isentropic and sigma coordinate hybrid numerical model - Model development and some initial tests
A solution is presented for matching boundary conditions across the interface of an isentropic and sigma coordinate hybrid model. A hybrid model based on the flux form of the primitive equations is developed which allows direct vertical exchange between the model domains, satisfies conservation principles with respect to transport processes, and maintains a smooth transition across the interface without need for artificial adjustment or parameterization schemes. The initial hybrid model simulations of a jet streak propagating in a zonal channel are used to test the feasibility of the hybrid model approach. High efficiency of the hybrid model is demonstrated.
Uccellini, L. W.↗