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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 NTRS1972

6300 A quantum efficiency of the recombination mechanism in the night-time F layer.

Simultaneous airglow and electron content measurements made at Hawaii are used to infer the number of 6300 and 6364 A quanta produced per electron lost in the nighttime F layer of the ionosphere. The equation of continuity of electrons is then solved numerically to obtain the electron density profile, and the amount of quenching is estimated. This leads to the number of excitations of O(super-1 D) per O2(+) recombination (epsilon). We find, for an exospheric temperature of 1100 K, epsilon is equal to 1.1 plus or minus 0.6, in good agreement with Zipf's laboratory measurement at 300 K.

Brown, W. E.↗
NASA NTRS1972

Radiative transition probabilities and recombination coefficients of the ion C IV.

Bound-bound and bound-free radiative transition probabilities, as well as radiative recombination coefficients of the ion C IV, are computed with a semi-empirical polarization potential method. The nonhydrogenic probabilities and coefficients are given for all bound states of the ion up to the principal quantum number n = 7.

Leibowitz, E. M.↗
NASA NTRS1971

Recombination luminescence in irradiated silicon - Effects of thermal annealing and lithium impurity.

Use of luminescence in irradiated silicon to determine the thermal stability of the defects responsible for the recombination. It is found that the defect responsible for the zero-phonon line at 0.97 eV has an annealing behavior similar to that of the divacancy and that the zero-phonon line at 0.79 eV anneals in a manner similar to the G-15 or K-center. Annealing at temperatures up to 500 C generates other defects whose luminescence is distinct from that seen previously. Addition of lithium to the material produces defects with new characteristic luminescence. Of particular importance is a defect with a level at E sub g -1.045 eV.

Johnson, E. S.↗
NASA NTRS1972

Kinetics of O/super 3P/ + CO + M recombination.

Measurement of rate coefficients over the temperature range from 250 to 370 K for the three-body recombination of O(super 3P) with CO. Earlier results at 300 K have been re-evaluated and were found to have been influenced by unknown impurities in the CO, which have now been removed by more elaborate purification methods. For CO as the third body, the rate constant is given by K = 6.5 x 10 to the minus 33rd exp (-4340 plus or minus 550/RT) cm to the 6th power per sq molecule per sec. For N2 and CO2, the 296 K rate constants are 2.3 and 6.2 x 10 to the minus 36th cm to the 6th power per sq molecule per sec, respectively.

Slanger, T. G.↗
NASA NTRS1972

Low temperature recombination and trapping analysis in high purity gallium arsenide by microwave photodielectric techniques

Some physical theories pertinent to the measurement properties of gallium arsenide are presented and experimental data are analyzed. A model for explaining recombination and trapping high purity gallium arsenide, valid below 77 K is assembled from points made at various places and an appraisal is given of photodielectric techniques for material property studies.

Khambaty, M. B.↗
NASA NTRS1973

Atomic recombination rate determination through heat-transfer measurement.

A theoretical and experimental demonstration is presented which shows that under suitable conditions the volume recombination coefficient can be determined by measuring the heat transfer rate into the wall of a cylinder through which a dissociated stream is passing. The experimental results obtained are in agreement with those of other investigators.

Park, C.↗
NASA NTRS1975

Dielectronic recombination and abundances near quasars

Major obstacles to determining certain elemental abundances associated with some quasars are (1) a lack of accurately measured helium line intensities, and (2) uncertainty about the extent to which dielectronic recombination, i.e. C(+3) + e(-) yields C(+2), is suppressed at the relevant gas and radiation densities. Some calculated results are presented in an attempt to reduce the latter obstacle.

Davidson, K.↗
NASA NTRS1976

Cooling and recombination processes in cometary plasma

The ion electron plasma in comets is examined for cooling processes which result from its interactions with the neutral coma. A cometary coma model is formulated that is composed predominantly of H2O and its decomposition products where electrons are cooled in a variety of processes at rates varying with energy. It is shown that solar plasma plus accumulated cometary ions and electrons is affected very strongly as it flows into the coma. The electrons are rapidly cooled and all but some 10% of the ions undergo charge exchange. Photodissociation of H2O is assumed where ion electron recombination is the dominant loss process.

Wallis, M. K.↗
NASA NTRS1975

Experimental study of the C/3P/ + N/4S/ + M yields CN/B 2Sigma+/ + M recombination

The kinetics of the CN violet band emission produced by the reaction of nitrogen with cynogen is investigated as a function of the densities of atomic carbon and atomic nitrogen and of total pressure. It is shown that CN is formed in a three-body recombination reaction from C and N atoms. The reactions studied have relevance to investigations of the chemistry of interstellar molecules.

Washida, N.↗
NASA NTRS1976

Recombination of NO/+/ in the ionosphere

Simultaneous nighttime measurements of ion and neutral concentrations and temperatures made by the Atmosphere Explorer-C satellite were used to determine the recombination rate coefficient of NO(+) as a function of electron temperature. The results agree in shape and absolute magnitude to within one standard deviation with those of Walls and Dunn (1974), indicating that NO(+) ions in the ionosphere may be in the ground vibrational state.

Torr, D. G.↗
NASA NTRS1976

Carbon recombination line observations of the sharpless 140 region

Carbon recombination-line emission has been detected at two frequencies from a dark cloud contiguous with the small H II region Sharpless 140. The observations show the dark cloud to be of unusually low temperature and to have a markedly inhomogeneous density distribution, with localized region of high density surrounding one or more embedded stars. The carbon is probably ionized by photons from both the exciting star of S140 and the embedded stars. The dark cloud and S140 apparently represent two stages of star formation which have occurred over a period of at least 500,000 years in adjacent regions of the same dark cloud.

Knapp, G. R.↗
NASA NTRS1976

Storage and recombination of atomic H in solid H2

A phenomenological rate process theory is developed for the storage and rapid recombination of atomic hydrogen free radicals in a crystalline molecular hydrogen solid at temperatures in the range of about 0.1-4 K. It is shown that such a theory can account quantitatively for the recently observed dependence of the storage time on the storage temperature, for the maximum concentration of trapped H atoms, and for the time duration of the energy release in the tritium decay experiments of Webeler. The theory predicts that maximum atomic hydrogen concentrations of the order 10 to the 20th per cu cm are realizable for storage temperatures in the vicinity of 0.14 K.

Rosen, G.↗
NASA NTRS1977

The yield of N/2D/ atoms in the dissociative recombination of NO/+/

The quantum yield or branching ratio of N(2D) atoms formed in the reaction e + NO(+) yields N + O was measured to be 76% plus or minus 6%. Photoionization of buffered nitric oxide by a flash lamp was studied using time-resolved atomic absorption. Atoms were produced both by direct photodissociation and by dissociative recombination, and these two effects were separated by means of SF6 as an electron scavenger.

Kley, D.↗
NASA NTRS1978

The recombination velocity at III-V compound heterojunctions with applications to Al (x) Ga(1-x)As-GaAs(1-y)Sb(y)

Interface recombination velocity in AlxGa1-xAs-GaAs and A10.85 Ga0.15As-GaAs1-ySby heterojunction systems was studied as a function of lattice mismatch. The results are applied to the design of highly efficient III-V heterojunction solar cells. A horizontal liquid-phase epitaxial growth system was used to prepare p-p-p and p-p-n double heterojunction test samples with specified values of x and y. Samples were grown at each composition, with different GaAs and GaAsSb layer thicknesses. A method was developed to obtain the lattice mismatch and lattice constants in mixed single crystals grown on (100) and (111)B oriented GaAs substrates.

Kim, J. S.↗
NASA NTRS1977

Auroral recombination of N and O - A possible source for emission in the gamma and delta bands of NO

Radiative recombination of N and O provides a significant source for auroral emission in the gamma and delta bands of NO with selective population of vibrational levels in the A 2 Sigma(+) and C 2 Pi states. This mechanism may account for emissions detected near 2150 A. Models are derived for the auroral ionosphere and include estimates for the concentrations of N and NO. The concentration of NO is estimated to have a value of about 100 million per cu cm near 140 km in an IBC III aurora. The corresponding density for N is about 50 million per cu cm, and the concentration ratio NO(+)/O2(+) has a value of about 5.5.

Wofsy, S. C.↗
NASA NTRS1978

Exact results on the temperature dependence of the specific equilibrium recombination rate coefficient

Two theorems based on Laplace transforms are used to relate threshold and high energy behavior to a temperature dependent variable. A recombination reaction involving electrically neutral species is presented to illustrate the dynamics of the activation energy and the associated rate coefficient. The distribution functions are shown to correspond with those predicted by Boltzmann's equations.

Mickens, R. E.↗
NASA NTRS1978

The effect of N2/+/ recombination on the aeronomic determination of the charge exchange rate coefficient of O/+//2D/ with N2

The Atmosphere Explorer (AE) data are reexamined in the light of new laboratory measurements of the N2(+) recombination rate coefficient alpha. The new measurements support earlier measurements which yielded values of alpha significantly lower than the AE values. It is found that the values for alpha determined from the satellite data can be reconciled with the laboratory measurements, if the charge exchange rate coefficient for O(+)(2D) with N2 is less than one-quarter of that derived in the laboratory by Rutherford and Vroom (1971).

Torr, D. G.↗
NASA NTRS1978

H109-alpha recombination line observations of S187 and of S298

The H109-alpha recombination line has been detected in S187 and S298. These observations and previously reported 6-cm continuum observations have been used to derive the large-scale properties of the core-envelope-type structure of these nebulae. An electron temperature of 9750 K and a core-to-envelope electron density ratio of 4 are derived for S298. In S187 an electron temperature of 6200 K and a core-to-envelope electron density ratio of greater than 10 are found. The relationship of the common centrally condensed structure of H II regions to the morphology of dark cloud complexes is considered.

Rossano, G. S.↗