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NASA NTRS1976

Carbon dioxide as working gas for laboratory plasmas

Measurements with a RF probe, retarding potential analyzer and mass spectrometer in a laboratory plasma tank were performed using the gases CO2, N2, A and He in order to compare their properties as working gases for laboratory plasma production. The overall result of that CO2 leads to higher plasma densities at lower neutral-gas pressures as well as to a larger Maxwellian component of the electron population, while the electron temperature is lower than that when N2, A and He are used.

Kist, R.↗
NASA NTRS1976

Adsorbate densities on /100/W

Auger electron spectroscopy and flash desorption mass spectrometry were used to determine the relative saturation densities of C, O, H, and N atoms on (100)W from adsorption of O2, H2, N2, CO, NO, and H2O. Particular attention is given to a discussion of the densities of CO, N2, and H2. It is found that no models of the structure of H2 on (100)W are consistent with all of the experimental data on this system, but a density of 1.5 times 10 to the 15th atoms per sq cm suggests that sites of fourfold coordination may be more likely than bridge-bonded sites of twofold coordination. For the other adsorbates, the measurements are in good agreement with previously assumed densities and they confirm that adsorbate densities are simple multiples or fractions of substrate atom densities.

Viswanath, Y.↗
NASA NTRS1976

Denitrogenation interruptions with air

A 3-h denitrogenation period at ground-level pressure with 95% O2-5% N2, with an air interruption of 5 min or more and matched with additional denitrogenation time equal to the interruption, will later result occasionally in altitude decompression sickness ('bends') during a 2-h decompression exposure at 3.8 psia (10,058 m equivalent) with 92% O2- 8% N2. Thus the equal time or 'mirror-image' make-up time for loss of denitrogenation did not prevent bends 7 times in 17 subjects during 71 exposures with air interruptions; on the other hand, no case of bends was reported after uninterrupted denitrogenation periods. Nitrogen-loading during the interruptive period is believed to resupply the bends sites with additional nitrogen, which re-establishes conditions favoring a return to a high incidence of bends.

Cooke, J. P.↗
NASA NTRS1976

Geomagnetic storm effects on the thermosphere and the ionosphere revealed by in situ measurements from OGO 6

The temporal response of the densities of upper-atmospheric ion and neutral constituents to a particular geomagnetic storm is studied using simultaneous ion and neutral-composition data obtained by the OGO 6 satellite during consecutive orbits at altitudes greater than 400 km. The investigated constituents include H(+), O(+), N2, O, He, and H. Derivation of the H density is reviewed, and the main effects of the storm are discussed, particularly temporal and global variations in the densities. It is found that: (1) the H and He densities began to decrease near the time of sudden commencement, with the decrease amounting to more than 40% of the quiet-time densities during the maximum stage at high latitudes; (2) the O and N2 densities exhibited an overall increase which began later than the change in H and He densities; (3) the H(+) density decreased differently in two distinct regions separated near the low-latitude boundary of the light-ion trough; and (4) the O(+) density showed an increase during earlier stages of the storm and decreased only in the Northern Hemisphere during the recovery phase. Certain physical and chemical processes are suggested which play principal roles in the ionospheric response to the storm

Marubashi, K.↗
NASA NTRS1976

Studies of molecular nitrogen bands from airborne auroral spectroscopy

Absolute auroral emission rates of several bands of the 1 PG (first positive), 2 PG, and Vegard-Kaplan systems of N2 and of the 1 NG (first negative) system of N2(+) were obtained from simultaneous spectral scans of two Ebert spectrophotometers mounted on board the NASA CV 990 aircraft. Analysis of these bands emitted during a 2-min auroral event leads to some conclusions regarding the excitation mechanisms of the C(3)Pi, B(3)Pi, and A(3)Sigma levels: the v' = 0 to v' = 3 levels of the C(3)Pi electronic state are populated by electron impact; the cross sections predict absolute emission rates that are in good agreement with the observations. Cross sections for excitation of the v' = 4 to v' = 8 levels, derived from laboratory measurement of the optical excitation functions, predict well the 1 PG bands observed in the auroral event.

Rees, M. H.↗
NASA NTRS1976

Gas interaction effects on lunar bonded particles and their implications

Results are reported for an experimental investigation of gas-interaction effects on different Apollo 11 and Apollo 12 lunar-soil samples containing bonded particles. In the experiments, lunar fines were exposed to pure O2, pure water vapor, HCl, NH3, N2, HCOOH, and CH3NH2, in order to observe whether bonded particles would separate. In addition, repeated gas adsorption/desorption measurements were performed to determine the nature and reactive properties of the particle surfaces, and surface areas were measured for comparison with analogous terrestrial samples to determine whether the surface areas of highly radiation-damaged particles were larger or smaller. It is found that N2 is apparently ineffective in separating bonded particles and that the ratio of Apollo 11 to Apollo 12 bonded particles separated by a particular gas exposure ranges from 2.5 to 3.0. Possible reasons for differences in material surface properties at the two Apollo sites are considered, and it is concluded that material from a certain depth at some other site was transported to the Apollo 12 site and mixed with the original material in recent years (considerably less than 2000 years ago).

Mukherjee, N. R.↗
NASA NTRS1977

The extreme ultraviolet /750-1230 A/ spectrum of an aurora

Extreme ultraviolet auroral spectra have been obtained in the wavelength range of 750-1230 A resolution with a rocket-borne grating spectrometer. Atomic emissions of N I, N II, O I and O II are the dominant features along with geocoronal H I Lyman alpha. N2 emission bands, which appear strongly in laboratory electron impact spectra, appear only as a modest background continuum between 900 to 1100 A. The observed intensities are consistent with electron impact excitation of O and N2. For optically thick emissions, such as N I at 1200 A, radiation transport along the arc results in an intensity enhancement when viewed through the arc towards the zenith.

Park, H.↗
NASA NTRS1977

High-latitude nitric oxide in the lower thermosphere

High-latitude observations of fluorescent nitric oxide gamma bands were made before and during a strong magnetic storm with the Ogo 4 ultraviolet spectrometer. Brightness measurements of the (1-0) gamma band of nitric oxide indicate a slow buildup of NO during the disturbed period. The NO column density reaches a value as high as a factor of 8 greater than the midlatitude value and shows no correlation with the brightness of the instantaneous aurora. A time-dependent model calculation indicates that the ionization and dissociation of N2 by auroral electrons can increase the NO and N(4-S) densities. This increase is dependent on the intensity and duration of the auroral precipitation and on the branching ratio of N(2-D) production by dissociation of N2. A steady state is not reached for NO until 100,000 sec in an aurora characterized by an energy flux of 10 ergs per sq cm sec. Dissociation by the solar ultraviolet radiation competes with horizontal and vertical transport as a loss process for the nitric oxide produced by the aurora. A high NO(plus)/O2(plus) ratio is to be expected in the period following a strong auroral precipitation.

Gerard, J.-C.↗
NASA NTRS1977

Rate constant for formation of chlorine nitrate by the reaction ClO + NO2 + M

The pseudo-first-order decay of ClO in a large excess of NO2 was monitored in a discharge flow/mass-spectrometer apparatus in order to measure the rate constant of the reaction ClO + NO2 + M yields ClONO2 + M for M = He, Ar, and N2 over the temperature range from 248 to 417 K. Numerical results are given for He at 248, 299, 360, and 417 K (1 to 9 torr); for Ar at 298 K (1 to 4 torr); and for N2 at 299, 360, and 417 K (1 to 6 torr). Systematic errors are estimated, and identification of the reaction product is discussed. The results obtained are shown to be in excellent agreement with other recent measurements of the same rate constant.

Leu, M. T.↗
NASA NTRS1977

Global exospheric temperatures and densities under active solar conditions

Temperatures measured by the OGO-6 satellite using the 6300 A airglow spectrum are compared with temperatures derived from total densities and N2 densities. It is shown that while the variation of the total densities with latitude and magnetic activity agree well with values used for CIRA (1972), the temperature behavior is very different. While the temperatures derived from the N2 density were in much better agreement there were several important differences which radically affect the pressure gradients. The variation of temperature with magnetic activity showed seasonal and local time variations. Neutral temperature, density, pressure and boundary oxygen variations for the storm of 8 March 1970 are presented.

Nisbet, J. S.↗
NASA NTRS1977

Observations of neutral composition and related ionospheric variations during a magnetic storm in February 1974

The neutral-atmosphere composition experiment on Atmosphere Explorer C measured N2, O, Ar, and He densities during a magnetic storm at altitudes down to about 160 km. At latitudes above 45 deg N, N2 and Ar densities generally increase during the storm, while He and O densities decrease. Below 45 deg N all densities tend to increase during the storm. The density increases at perigee indicate that density- or temperature-profile changes are taking place below 160 km. The return to prestorm conditions is very slow, demonstrating the integrating effect of the atmospheric response. A recent theoretical model incorporating thermospheric circulation and diffusion effects reproduces the longitudinally averaged data, including latitude trends and the asymmetry about the storm maximum. Comparison with the mass-spectrometer and incoherent-scatter empirical model shows qualitative agreement with latitude trends but not with storm asymmetry, while the earlier J71 model based on total mass density is not in agreement with observed latitudinal trends. A close correlation is found between in situ O/N2 measurements and in situ and ground-based ionosonde measurements of electron density.

Hedin, A. E.↗
NASA NTRS1977

The Viking gas exchange experiment results from Chryse and Utopia surface samples

Immediate gas changes occurred when untreated Martian surface samples were humidified and/or wet by an aqueous nutrient medium in the Viking lander gas exchange experiment. The evolutions of N2, CO2, and Ar are mainly associated with soil surface desorption caused by water vapor, while O2 evolution is primarily associated with decomposition of superoxides inferred to be present on Mars. On recharges with fresh nutrient and test gas, only CO2 was given off, and its rate of evolution decreased with each recharge. This CO2 evolution is thought to come from the oxidation of organics present in the nutrient by gamma Fe2O3 in the surface samples. Atmospheric analyses were also performed at both sites. The mean atmospheric composition from four analyses is N2, 2.3%; O2, not greater than 0.15%; Ar, 1.5% and CO2, 96.2%.

Oyama, V. I.↗
NASA NTRS1977

Nitrogen-induced absorption of oxygen in the Herzberg continuum

Total absorption of O2 induced by collisions with N2 has been measured at room temperature in the Hersberg continuum using a one meter normal incidence grating monochromator. The enhanced absorption is ascribed to the formation of O2-O2 and O2-N2 dimers. The interaction constants for these dimers are determined and utilized to investigate their effect on the absorption of solar radiation in the stratosphere.

Shardanand, MR.↗
NASA NTRS1977

Product distributions for some thermal energy charge transfer reactions of rare gas ions

Ion cyclotron resonance methods were used to measure the product distributions for thermal-energy charge-transfer reactions of He(+), Ne(+), and Ar(+) ions with N2, O2, CO, NO, CO2, and N2O. Except for the He(+)-N2 reaction, no molecular ions were formed by thermal-energy charge transfer from He(+) and Ne(+) with these target molecules. The propensity for dissociative ionization channels in these highly exothermic charge-transfer reactions at thermal energies contrasts with the propensity for formation of parent molecular ions observed in photoionization experiments and in high-energy charge-transfer processes. This difference is explained in terms of more stringent requirements for energy resonance and favorable Franck-Condon factors at thermal ion velocities.

Anicich, V. G.↗
NASA NTRS1978

A search for nitric oxide gamma band emission in an aurora

A strong emission feature at 2150 A has been observed by a rocket-borne spectrophotometer in an IBC II(+) aurora. This feature, commonly identified with the NO gamma (1,0) band, is comparable in intensity to the nearby N2 Vegard-Kaplan bands. Comparison of the observed spectra with a theoretically produced synthetic spectrum allows all but this feature to be assigned to N2 transitions. No bands of the v prime = 0 or 2 progressions or any other bands from v prime = 1 appear, casting serious doubt on the identification of this feature as the NO gamma (1,0) band.

Beiting, E. J., III↗
NASA NTRS1978

Fretting wear of iron, nickel, and titanium under varied environmental conditions

Fretting wear experiments were conducted on high purity iron, nickel and titanium in air under conditions of varied humidity and temperature, and in nitrogen. For iron and titanium, maximum fretting occurred at 10 and 30 percent relative humidity respectively. Nickel showed a minimum in fretting wear at about 10 percent relative humidity. With increasing temperature, all three metals initially showed reduced fretting wear, with increasing wear observed as temperatures increased beyond 200-300 C. For titanium, dramatically reduced fretting wear was observed at temperatures above 500 C, relatable to a change in oxidation kinetics. All three metals showed much less fretting wear in N2 with the presence of moisture in N2 having a proportionally stronger effect than in air.

Bill, R. C.↗
NASA NTRS1978

A Titan atmosphere with a surface temperature of 200K

The brightness temperature of Titan at 3 mm wavelength is around 200 K according to Ulich, Conklin, and Dickel (1978). Although an earlier measurement by Briggs is much colder, 200 K as the surface temperature was used to build an atmospheric model with a surface pressure of 21 bars. CH4 clouds form between 100 and 120 km altitude. The visual limb is near 200 km. The methane mixing ratio is 0.25 percent above the clouds and 7 percent below; the dominant gas is assumed to be N2. The thermal opacity is due to pressure-induced absorption in N2 and a trace (0.5 percent) of H2, with some help from cloud particles; unit opacity is reached at 600 mbar, 110 km from the surface. The radius of the solid body in this model is 2700 km, in reasonable agreement with 2600 km obtained if the density is the same as that of Ganymede and Callisto.

Hunten, D. M.↗
NASA NTRS1979

Molecules of significance in planetary aeronomy

This monograph is basically devoted to spectroscopic information of the molecules of planetary interest. Only those molecules have been dealt with which have been confirmed spectroscopically to be present in the atmosphere of major planets of our solar system and play an important role in the aeronomy of the respective planets. An introduction giving the general conditions of planets and their atmospheres including the gaseous molecules is given. Some typical planetary spectra is presented and supported with a discussion on some basic concepts of optical absorption and molecular parameters that are important to the study of planetary atmospheres. Quantities like dipole moments, transition probabilities, Einstein coefficients and line strengths, radiative life times, absorption cross sections, oscillator strengths, line widths and profiles, equivalent widths, growth curves, bond strengths, electronic transition moments, Franck-Condon factors and r-centroids, etc., are discussed. Spectroscopic information and relevant data of 6 diatomic (HF, HCL, CO, H2, O2, N2) and 6 polyatomic (CO2, N2), O3, HeO, NH3, CH4) molecules are presented.

Mohan, H.↗