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Brown, L. R.

Publications and source records attributed to Brown, L. R..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Local Mode Axis Tilting in H(sub 2)S

Despite the computational efficiency of conventional normal mode techniques for the analysis of rotational-vibrational spectra, the overtone bands of small symmetrical hydrides have certain features that favour an alternative local mode interpretation.

Axis Tilt↗
NASA NTRS1996

The Atmospheric Trace Molecule Spectroscopy (ATMOS) Experiment: Deployment on the ATLAS Space Shuttle Missions

The ATMOS Fourier transform spectrometer was flown for a fourth time on the Space Shuttle as part of the ATLAS-3 instrument payload in November 1994. More than 190 sunrise and sunset occultation events provided measurements of more than 30 atmospheric trace gases at latitudes 3 - 49 deg N and 65 - 72 deg S, including observations both inside and outside the Antarctic polar vortex. The instrument configuration, data retrieval methodology, and mission background are described to place in context analyses of ATMOS data presented in this issue.

Gunson, M. R.↗
NASA NTRS1996

Temperature Dependence of Nitrogen Broadening of the NO Fundamental Vibrational Band

We report measured N2-broadening coefficients, gamma (T), of approximately 70 transitions of the ground electronic state fundamental vibration-rotation band (v=1 (left arrow) 0) of NO at 183, 213 and 296K. In addition to the broadening asymmetry previously observed between the 2 pi 3/2 and 2 pi 1/2 state transitions, we also observed for most of the 2 pi 1/2 transitions an increased broadening of the f-lambda over e-lambda components. The temperature dependence of the broadening coefficients was characterized by the power law, gamma T = gamma 296 (296/T) (sup n).

Spencer, M. N.↗
NASA NTRS1996

Empirical Line Parameters of NH(sub 3) from 4791 to 5294 cm(sup -1)

To support remote sensing of planetary atmospheres at 2??laboratory spectra of NH(sub 3) andf enriched (sup 14)NH(sub 3) and (sup 15)NH(sub 3) were recorded at 0.011 cm(sup -1) resolution with the McMath Fourier transform spectrometer (FTS) located at...

NH3 remote sensing planetary atmospheric study↗
NASA NTRS1996

The Hot Bands of Methane Between 5 and 10(micro)m

Experimental line intensities of 1727 transitions arising from nine hot bands in the pentad-dyad system of methane are fitted to first and second order using the effective dipole moment expansion in the polyad scheme. The observed bands are V3-V2, V3-V4, V1-V2, V1-V4, 2V4-V4, V2+V4-V2, V2+V4-V4, 2V2-V4, and the intensities are obtained from long-path spectra recorded with the Fourier transform spectrometer located at Kitt Peak National Observatory. For the second order model, some of the 27 intensity parameters are not linearly independant, and so two methods (extrapolation and effective parameters) are propopsed to model the intensities of the hot bands.

methane hot bands dipole moment expansion Kitt Pea↗
NASA NTRS1996

The High Resolution Infrared Spectrum of CH(sub 3)D in the Region 900-1700 cm(sup -1)

The high resolution absorption spectrum of CH(sub 3)D in the region of 900-1700 cm(sup -1) has been revisited on the basis of new long path experimental data recorded with the Fourier transform spectrometer at Kitt Peak. A theoretical model used previously for spherical rotors has been adapted for polyatomic molecules in order to analyze the vibrational polyads of CH(sub 3)D simultaneously.

methane atmosphere study spectroscopy↗
NASA NTRS1995

The No Vibrational Fundamental Band: Temperature Dependence of N2- Broadening Coefficients

Rovibrational spectra of the vibrational fundamental of nitric oxide have been recorded under N2-broadening conditions using the Solar McMath FTS at the Kitt Peak National Observatory. The temperature range for the experiments was 296K to 183K. Qualitative as well as quantitative discrepancies are observed between these experimental determinations of the temperature dependence.

nitric oxide broadening coefficients vibrational f↗
NASA NTRS1995

Spectroscopic Parameters of H2S Polyads Between 3400 and 8000 cm x 10 to -1 exponent

The absorption spectra of hydrogen sulfide from 0.8 to 5 micro- meters were recorded with three spectral resolutions using the Fourier transform spectrometer at Kitt Peak National Observatory. Twenty bands were previously assigned so that accurate band origins and vi- brational parameters could be determined. Described are the analyses of the rotational structure of resonating hydrogen sulfide states.

molecular spectroscopy hydrogen sulfide absorption↗
NASA NTRS1995

Measurements of Band Intensities, Herman-Wallis Parameters, and Self-Broadening Line-Widths of the 30011 - 00001 and 30014 - 00001 Bands of CO2 at 6503 cm(exp -1) and 6076 cm(exp -1)

Rotationless band intensities and Herman-Wallis parameters are listed in HITRAN tabulations for several hundred CO2 overtone-combination bands. These parameters are based on laboratory measurements when available, and on DND calculations for the unmeasured bands. The DND calculations for the Fermi interacting nv(sub 1) + v(sub 3) polyads show the a(sub 2) Herman-Wallis parameter varying smoothly from a negative value for the first member of the polyad to a positive value for the final member. Measurements of the v(sub 1) + v(sub 3) dyad are consistent with the DND calculations for the a(sub 2) parameter, as are our recent measurements of the 4v(sub 1) + v(sub 3) pentad. However, the measurement-based values in the HITRAN tables for the 2v(sub 1) + v(sub 3) triad and the 3v(sub 1) + v(sub 3) tetrad do not support the DND calculated values for the a(sub 2) parameters. We therefore decided to make new measurements to improve some of these intensity parameters. With the McMath FTS at Kitt Peak National Observatory/National Solar Observatory we recorded several spectra of the. 4000 to 8000 cm(exp -1) region of pure CO2 at 0.011 cm(exp -1) resolution using the 6 meter White absorption cell. The signal/noise and absorbance of the first and fourth bands of the 3v(sub 1) + v(sub 3) tetrad of C-12O-16 were ideal on these spectra for measuring line intensities and broadening widths. Our selfbroadening results agree with the HITRAN parameterization, while our measurements of the rotationless band intensities are about 15% less than the HITRAN values. We find a negative value of a(sub 2) for the 30011-00001 band and a positive value for the 30014-00001 band, whereas the HITRAN values of a(sub 2) are positive for all four tetrad bands. Our a(sub 1) and a(sub 2) Herman-Wallis parameters are closer to DND calculated values than the 1992 HITRAN values for both the 30011-00001 and the 30014-00001 band.

Giver, L. P.↗
NASA NTRS1995

The Rovibrational Intensities of the (40 deg 1) and (00 deg 0) Pentad Absorption Bands of 12C16O2 Between 7284 and 7921 cm(exp-1)

Carbon dioxide is the major constituent of the atmospheres of both Mars and Venus. Correct interpretations of spectra of these atmospheres require accurate knowledge of a substantial number of absorption bands of this gas. This is especially true for Venus; many weak CO2 bands that are insignificant in the earth's atmosphere are prominent absorbers in Venus' hot, dense lower atmosphere. Yet, recent near-infrared spectra of Venus' nightside have discovered emission windows, which occur between CO2 absorption bands, at 4040-4550 cm(exp-1), 5700-5900 cm(exp-1), and several smaller ones between 7500 and 9400 cm(exp-1). This radiation is due to thermal emission from Venus' lower atmosphere, diminished by scattering and absorption within the sulfuric acid clouds on its way to space. Simulations of these data with radiative transfer models can provide improved information on the abundances of a number of constituents of the lower atmosphere (e.g. H2O, CO, HDO, HCl, HF, and OCS) and the optical properties of the clouds, whose spatial variation modulates the brightness of the emissions. However, the accuracy of these retrievals has been limited by insufficient knowledge of the opacity of some of the gas species, including CO2, at the large pathlengths and high temperatures and pressures that exist on Venus. In particular, modeling the emission spectrum did not produce a good fit for the emission window centered at 7830 cm(exp-1). In an ongoing effort to assist analyses of these Venus spectra, we have been making laboratory intensity measurements of several weak bands of CO2 which are significant absorbers in these Venus emission windows. The CO2 bands that are prominent in the 7830 cm(exp-1) region belong to the vibrational sequence 4v1+v3 and associated hot bands. Only 2 of the 5 bands of this sequence have been previously measured. Modeling Venus' emission spectrum in the 7830 cm(exp-1) region had to rely on calculated intensity values for the weak ground state band at 7921 cm-1 and the associated hot bands. Since the calculated intensities of ground state bands are known to have significant uncertainties, we decided to measure this (40 deg 1)I (left arrow) (00 deg 0) band with the Ames 25 meter multiple reflection absorption cell and Fourier transform spectrometer. We also measured the (40 deg 1) (sub IV) (left arrow) (00 deg 0) band at 7460 cm(exp-1), which also had not been previously measured. These measurements are reported in this article, and we also give our reanalysis of the prior measurements of the (40 deg 1) (sub III) (left arrow) (00 deg 0) bands. These measurements provide the basis for improving calculated intensities for related hot bands as well as simulations of Venus' spectrum.

Giver, L. P.↗
NASA NTRS1995

The No Vibrational Fundamental Band: Temperature Dependence of N2-Broadening Coefficients

Rovibrational spectra of the vibrational fundamental of nitric oxide have been recorded under N2-broadening conditions at 0.0056 cm(exp-1) resolution using the Solar McMath FTS at the Kitt Peak National Observatory. The temperature range for the experiments was 296 K to 183 K. The 30 cm absorption cell used for the measurements is cooled with a helium compressor and can operate at temperatures down to 60 K; vibration isolation of the cell allows its use with high performance Fourier Transform Spectrometers. From these spectra, N2-broadened line widths have been determined thru m = 16.5. Qualitative as well as quantitative discrepancies are observed between our experimental determinations of the temperature dependence of the broadening and theoretical calculations.

Spencer, M. N.↗
NASA NTRS1995

Positions and Intensities in the 3v2/v2+v4 Vibrational System of 14NH3 Near 4 micron meters

Ammonia is the fourth most abundant constituent in the atmospheres of Jupiter and Saturn, after hydrogen, helium and methane. This relative abundance is attested by the presence in the infrared planetary spectra of many absorption features observed in the range of fundamental bands and also in the higher bands. Reported are experimental line positions and intensities of selected ammonia bands.

ammonia Jupiter Saturn spectroscopy planetary gass↗