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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Stratospheric measurements of CF2Cl2 and N2O

Concentrated samples of stratospheric air were obtained at pressure altitudes of 18.3 km and 21.3 km aboard U-2 aircraft, and at 28.3 km and 35.9 km aboard a balloon platform. The mixing ratios of CF2Cl2 and N2O are reported for locations in California, Oregon, Texas, and Quebec, Canada. The observed mixing ratios compare within a factor of 2 to those reported by other investigators and show a more rapid decrease with altitude than predicted by a two-dimensional model.

Tyson, B. J.↗
NASA NTRS1978

Spectral studies of SiCl4 + N2O + Ar and SiH4 + Ar mixtures in a shock tube in 160-550 nm range

Gases containing SiO, SiO2, SiH, and Si2 were produced in the reflected-shock region of a shock tube by heating SiCl4 + N2O + Ar and SiH4 + Ar mixtures with shock waves. Spectral absorption characteristics were measured in the 160-550 nm wavelength range and in the 2800-3600 K temperature range and compared to calculated values. The sums of the squares of electronic transition moments at equilibrium separation were derived. It was found that absorption by SiO2 and other known bands of SiO, SiH, and Si2 were too weak to be measured. The cross section of absorption by a continuum, believed due to SiH, varied from 2.5 x 10 to the -17th sq cm at 280 nm to 1.6 x 10 to the -18th sq cm at 440 nm.

Park, C.↗
NASA NTRS1979

K-shell photoabsorption coefficients of O2, CO2, CO, and N2O

The total photoabsorption coefficient has been measured from 500 to 600 eV around the K edge of oxygen in gases O2, CO2, CO, and N2O by means of a gold continuum source and crystal spectrometer with better than 1-eV resolution. The cross sections are dominated by discrete molecular-orbital transitions below the K-edge energy. A few Rydberg transitions were barely detectable. Broad shape resonances appear at or above the K edge. Additional broad, weak features above the K edge possibly arise from shake up. Quantitative results are given that have about 10% accuracy except on the very strong peaks. All the measured features are discussed in relation to other related measurements and theory.

Barrus, D. M.↗
NASA NTRS1980

The spectrum of N2O between 800 and 5200 cm(-1)

An atlas of N2O lines between 800 and 5200/cm obtained from low-pressure, long-path-length samples at 296K is presented. Many of the line centers were marked and their positions were tabulated. The peak absorptances of the weaker lines in the atlas are similar to those expected in an extreme path through the atmosphere.

Hawkins, R. L.↗
NASA NTRS1981

Simultaneous spectroscopic determination of the latitudinal, seasonal, and diurnal variability of stratospheric N2O, NO, NO2, and HNO3

A program for the measurement of latitudinal, seasonal, and diurnal variations in stratospheric N2O, NO, NO2 and HNO3 is described, which uses airborne Fourier transform absorption spectroscopy to simultaneously determine columns, above 12 km, of the four molecules. The data may prove useful for comparison with two-dimensional models of stratospheric chemistry, since simultaneous measurement of several species with the same technique provides an inherently more reliable set for model comparisons, by eliminating uncorrelated atmospheric variability and reducing differences in instrumental biases.

Coffey, M. T.↗
NASA NTRS1981

Measurements of CF2Cl2, CFCl3, and N2O in the lower stratosphere between 2 deg S and 73 deg N latitude

Mixing ratios are presented for CF2Cl2, CFCl3, and N2O in the lower stratosphere. They are derived from measurements made on samples collected by a high-altitude aircraft during a survey in the northern hemisphere in the summer of 1977. The vertical distributions of the mixing ratios of these species show a decrease with increasing altitude and a marked decrease at a given altitude with increasing latitude from 2 deg S to 73 deg N latitude. These results agree with measurements at similar latitudes in the fall of 1976 and with results of other experiments. The experimental apparatus and procedures are described in greater detail than in previous papers.

Vedder, J. F.↗
NASA NTRS1982

Nitrogen, oxygen and air broadened widths and relative intensities of N2O lines near 2450/cm

Spectra of the v sub 1 + 2v sub 2 and the weak underlying v sub 1 + 3v sub 2 - v sub 2 band of N2O near 2450/cm were analyzed by the nonlinear, least squares, whole band technique. The oxygen, nitrogen, and air broadened line widths and the relative line intensities were determined. The air broadened widths, for/m/3, are in agreement with those in the 1980 AFGL line listing and the relative band intensities also agree, within about 20% with the values in this listing.

Hawkins, R. L.↗
NASA NTRS1983

Nitrogen-, oxygen-, and air-broadened widths and relative intensities of N2O lines near 2450 per cm

Spectra of the v sub 1 + 2v sub 2 and the weak underlying v sub 1 + 3v sub 2 - v sub 2 band of N2O near 2450/cm were analyzed by the nonlinear, least squares, whole band technique. The oxygen, nitrogen, and air broadened line widths and the relative line intensities were determined. The air broadened widths, for /m/3, are in agreement with those in the 1980 AFGL line listing and the relative band intensities also agree, within about 20 percent with the values in this listing. Previously announced in STAR as N82-30201

Hawkins, R. L.↗
NASA NTRS1984

Line strengths of N2O in the 1120-1440/cm region

Line strengths of N2O and its isotopic derivatives in the 1120-1440/cm region were measured at low pressure and high resolution (0.0054/cm). The band strength, rotationless dipole moment matrix elements, and F factor coefficients were considered. First-order nondegenerate perturbation theory was employed to derive explicit expressions for the rotationless dipole moment matrix elements and F factor coefficients. This made it possible to obtain general expressions for the F factor. The derived expressions were also applicable to CO2 bands.

Toth, R. A.↗
NASA NTRS1986

Diode laser measurements of line strengths and widths in the 4.5-micron bands of N2O

Line-strength measurements in the N2O nu3-fundamental region using a tunable diode-laser spectrometer. From these measurements and the Herman-Wallis factor determined by Boissy et al. (1975), the nu-3-fundamental band strength is found to be 1203 + or - 22 per sq cm atm at 297 K. Line-broadening parameters for two nu-3-fundamental lines were determined using nitrogen (N2) as the broadening gas. Measured strengths and N2 line-broadening parameters for several hot-band lines are also presented.

Lowenstein, M.↗
NASA NTRS1986

Frequencies of N2O in the 1100- to 1440/cm region

The vibration-rotation frequency parameters of vibrational states of several isotopic species of N2O were determined from IR spectra obtained with a high-resolution Fourier-transform spectrometer. The bands in the 1100 to 1440/cm region were considered. The line frequencies, observed for the lines of the species (N-14)2(O-16), (N-14)(N-15)(O-16), (N-15)(N-14)(O-16), (N-14)2(O-18), (N-14)2(O-17), and (N-15)2(O-16) were analyzed to obtain values of the absolute band centers and upper-state and lower-state rotational constants.

Toth, R. A.↗
NASA NTRS1987

N2O vibration-rotation parameters derived from measurements in the 900-1090- and 1580-2380/cm regions

Fourier-transform spectrometric measurements of the N2O IR spectrum in the 900-1090 and 1580-2380/cm regions were obtained at a 0.005/cm resolution, and line frequencies of eight species for several ground state bands and hot bands are analyzed to obtain values of band centers and upper-state effective rotational constants. Several bands are reported for the first time. Least-squares fits for the 0400-0000, 0420(e)-0000, and 0510-0110 bands of the (N-14)2O-16 species suggest perturbation of the high-J levels of the upper states. Resonance interactions were noted in transitions including the 1001-1000 bands of (N-14)2O-16 and N-15N-14O-16.

Toth, Robert A.↗
NASA NTRS1987

Simultaneous measurement of stratospheric O3, H2O, CH4, and N2O profiles from infrared limb thermal emissions

Thermal emission measurements of the earth's stratospheric limb were made with a cryogenically cooled high-resolution Michelson interferometer on a balloon flight launched from Palestine, TX, on Nov. 6, 1984. Infrared spectra for complete limb sequences were obtained over portions of the 700-1940/cm range with an unapodized spectral resolution of 0.03/cm for tangent heights varying from 13 to 39 km. The observed data from 1125 to 1425/cm have been analyzed for simultaneous measurement of O3, H2O, CH4, and N2O profiles. The analysis employs line-by-line and layer-by-layer radiative-transfer calculations, including curvature and refraction effects. The optimum use of geometric and spectral effects is made to obtain sharply peaked weighting functions. Contributions from stratospheric aerosol are included by measuring the light extinction within the window regions of the observed spectra. The retrieved constituent profiles are compared with measurements made with a variety of techniques by other groups. The comparison shows good agreement with the published data for all gases, indicating the capability of retrieving trace gas profiles from high-resolution thermal emission limb measurements.

Abbas, M. M.↗
NASA NTRS1988

Extremely low N2O concentrations in the springtime stratosphere at McMurdo Station, Antarctica

Measurements have been made of stratospheric N2O using the Stony Brook millimeter-wave remote sensing spectrometer at McMurdo Station, and NO2 mixing ratios are found that are less than 1.5 at 20 km and less than 1.10 at 25 km compared to values measured during the Antarctic summer. The observed mixing ratios are also much less than those predicted by global-scale models of stratospheric chemistry and dynamics. As the NO2 signal remained very weak when McMurdo was at the edges of the ozone hole and showed no signs of recovering during October, it is concluded that the geographical and temporal extent of the region of low NO2 is comparable to or greater than that of the ozone hole. These results argue against theories that require springtime upwelling to explain the Antarctic ozone hole. It is suggested that the air in the Antarctic lower stratosphere during late winter and early spring has been subjected to considerable downward transport.

Parrish, A.↗
NASA NTRS1989

Tunable diode laser measurements of absolute line strengths in the 2nu2 band of N2O near 8 microns

The absolute intensities of five rotational transitions in the 2nu2 band of N2O near 8 microns have been measured with a tunable-diode laser-spectrometer. Measurements were reproducible within an average deviation of about 3 percent, and the experimental and calculated line strengths differed by only 1.5 percent. An analysis of the line strengths has yielded a band strength of S(v) = 6.98 + or - 0.26/sq cm per atm at 296 K. The band and line strengths are in excellent agreement with two recently reported values obtained by using Fourier transform-IR spectroscopy.

Tang, Lai-Wa↗
NASA NTRS1989

Measurements of CH4, N2O, CO, H2O and O3 in the middle atmosphere by the ATMOS experiment on Spacelab 3

The volume mixing ratios of five minor gases (CH4, N2O, CO, H2O, and O3) were retrieved through the middle atmosphere from the analysis of 0.01/cm resolution infrared solar occultation spectra recorded near 28 N and 48 S latitudes with the ATMOS (Atmospheric Trace Molecule Spectroscopy) instrument, flown on board Spacelab 3. The results, which constitute the first simultaneous observations of continuous profiles through the middle atmosphere for these gases, are in general agreement with reported measurements from ground, balloon and satellite-based instruments for the same seasons. In detail, the vertical profiles of these gases show the effects of the upper and middle atmospheric transport patterns dominant during the season of these observations. The profiles inferred at different longitudes around 28 N suggest a near-uniform zonal distribution of these gases. Although based on fewer observations, the sunrise occultation measurements point to a larger variability in the vertical distribution of these gases at 48 S.

Gunson, M. R.↗
NASA NTRS1990

Dissociative attachment of electrons to N2O

Cross sections for the production of O(-) from N2O by the process of dissociative electron attachment have been measured for electron-impact energies ranging from 0 to 50 eV. Three new O(-) peaks are observed. The present data above 5-eV electron-impact energy differ considerably from the previous measurements.

Krishnakumar, E.↗
NASA NTRS1990

Measurements of CH4, N2O, CO, H2O, and O3 in the middle atmosphere by the Atmospheric Trace Molecule Spectroscopy Experiment on Spacelab 3

The volume mixing ratios of five minor gases (CH4, N2O, CO, H2O, and O3) have been retrieved through the middle atmosphere from the analysis of 0.01/cm resolution infrared solar occultation spectra recorded near 28 deg N and 48 deg S latitudes with the Atmospheric Trace Molecule Spectroscopy instrument, flow on board Spacelab 3 (April 30 through May 6, 1985). The results are in general agreement with reported measurements from ground-, balloon-, and satellite-based instruments for the same seasons. In detail, the vertical profiles of these gases show the effects of the upper and middle atmospheric transport patterns dominant during the season of these observations. The profiles inferred at different longitudes around 28 deg N suggest a near-uniform zonal distribution of these gases, for conditions corresponding to late spring. The sunrise occultation measurements point to a larger longitudinal variability in the vertical distribution of these gases at 48 deg S.

Gunson, M. R.↗