J. Ballard

The 1997 spectroscopic GEISA databank

The current version GEISA-97 of the computer-accessible database system GEISA (Gestion et Etude des Informations Spectroscopiques Atmospheriques: Management and Study of Atmospheric Spectroscopic Information) is described. This catalogue contains 1,346,266 entries. These are spectroscopic parameters required to describe adequately the individual spectral lines belonging to 42 molecules (96 isotopic species) and located between 0 and 22,656 cm-1. The featured molecules are of interest in studies of the terrestrial as well as the other planetary atmospheres, especially those of the Giant Planets. GEISA-97 contains also a catalog of absorption cross-sections of molecules such as chlorofluorocarbons which exhibit unresolvable spectra. The modifications and improvements made to the earlier edition (GEISA-92) and the data management software are described. GEISA-97 and the associated management software are accessible from the ARA/LMD (Laboratoire de Meteorologie Dynamique du CNRS, France) web site: http://ara01.polytechnique.fr/registration.

Spectral parameters of self- and hydrogen-broadened methane from 2000 to 9500 cm-1 for remote sounding of the atmosphere of Jupiter

Abstract Long-pathlength self- and H 2 -broadened absorption spectra of CH 4 have been recorded from 2000 to 9500 cm -1 at a resolution of 0.25 cm -1 . Thesespectra were obtained for a wide range of conditions relevant to the atmosphere of Jupiter, including nominal temperatures of 190, 240, and 296 K, pathlenghts from 64 to 512 m, and pressures from 0.2 to 700 torr, giving CH 4 column abundances from 0.016 to 530 m-amagat. A series of molecular band models were fitted to these spectra at 10 cm -1 resolution, showingthat the Goody and Malkmus random band models with the Voigt lineshape provided the best fits to the data. The Goody-Voigt model was subsequently used to calculate the level in the Jovian atmosphere that will be sounded by observations of CH 4 absorption, and estimates were made of the accuracy to be expected if this model were used to retrieve atmospheric parameters.

An intercomparison of laboratory measurements of absorption cross-sections and integrated absorption intensities for HCFC-22

Abstract An intercomparison of measurements of infra-red absorption cross-sections and integrated absorption intensities in HCFC-22 has been carried out. Independent measurements were made by five spectroscopy groups so that their experimental methods and data reduction techniques could be critically examined. The initial results showed a spread in reported values for integrated absorption intensity over the mid infra-red spectral region that were larger than the reported uncertainties. Re-examination of experimental and data reduction methods resulted in consistency of results within the reported errors. It was found that particular attention had to be paid to controlling and characterising errors associated with the non-linear response of MCT detectors and pre-amplifiers, adsorption of the sample on surfaces in the absorption cell, effectiveness of mixing when making measurements on mixtures of absorber gas and a buffer gas, and location of the photometric “full-scale” and “zero” levels.

A coolable long path absorption cell for laboratory spectroscopic studies of gases

Abstract A long path absorption cell (Long White Cell) which has been designed and built for laboratory spectroscopic studies of gases found in terrestrial and planetary atmospheres is described. Factors influencing the design and construction are discussed, including aspects of the optical, mechanical, cryogenic, vacuum, gas handling and safety systems, and the pressure and temperature monitoring systems. The practical capabilities of the cell include absorber pathlengths up to 512 m, gas sample pressures up to 5 bar and temperatures between 190 and 300 K, and the suitability for use with corrosive and flammable gases. The performance of the cell is discussed in relation to spectroscopic measurements of mixtures of gaseous methane and hydrogen.

Infrared band strengths and absorption cross-sections of HFC-32 vapour

Abstract Infrared absorbance cross-sections and integrated band strengths for HFC-32 (difluoromethane, CH 2 F 2 ) vapour have been determined from laboratory measurements at eight temperatures (203, 212, 222, 243, 253, 264, 287, and 297 K) for the region 600–1900 cm −1 at 0.03 cm −1 instrument resolution, by Fourier transform infrared spectroscopy. In addition, air-broadened spectra of HFC-32 vapour have been recorded at 203, 251, and 297 K at pressures of 5, 20, and 100 kPa air.

Observations of V = 1–0 emission from thermospheric nitric oxide by ISAMS

The Improved Stratospheric and Mesospheric Sounder (ISAMS) on the Upper Atmosphere Research Satellite (UARS) has made global measurements of emission from the 1→0 band of nitric oxide (NO), using a limb viewing geometry in which the tangent point is scanned from 0 km to >150 km. Vertical profiles of atmospheric radiance often show a peak around 120 km altitude, due to the relatively high temperatures and densities of NO(v=1) found in the lower thermosphere. In this letter we report on some aspects of the radiance from NO(v=1), in particular observations of the lower thermosphere during periods of quiet and intense geomagnetic activity.

Fourier transform infrared spectroscopy of HCFC-142b vapour

Abstract Infrared absorbance cross sections and integrated band strengths for HCFC-142b (1-chloro-1,1-difluoroethane, CH 3 CC1F 2 ) vapour have been determined at six temperatures (203, 213, 233, 253, 273 and 294 K) for the region 600–1500 cm −1 by Fourier transform infrared spectroscopy. Air-broadened spectra of HCFC-142b vapour have been recorded at 203, 253 and 294 K using mixtures containing 5, 20 and 100 kPa dry air. Spectroscopic resolution was 0.03 cm −1 , with additional high resolution (0.002 cm −1 ) measurements of the pure vapour at 203 and 294 K.

INFRARED ABSORPTION CROSS-SECTIONS AND INTEGRATED ABSORPTION INTENSITIES OF HFC-134 AND HFC-143A VAPOUR

Abstract Infrared absorption cross-sections and integrated absorption intensities of HFC-134 (1,1,2,2-tetrafluoroethane) and HFC-143a (1,1,1-trifluoroethane) vapour have been determined from laboratory measurements at six temperatures (203, 213, 233, 253, 273 and 297 K) for the region 560–1900 cm −1 (5.3–17.9 μm) at 0.03 cm −1 instrument resolution, by Fourier transform infrared spectroscopy. In addition, air-broadened spectra have been recorded at 297 K and pressures of 5, 20 and 100 kPa air. Inter-comparisons between this work and previous studies have been made where possible.

Band parameters and k coefficients for self-broadened ammonia in the range 4000–11 000 cm-1

Analysis of the near-infrared spectra of the outer planets is hampered by the scarcity of reliable line data for methane and ammonia which both have very complicated spectra in this region. Until reliable line data is gathered, band models which are based upon the laboratory measurement of the transmission spectra of the gases under conditions similar to those found in planetary atmospheres must be used. This has been done extensively for methane by previous investigators but analysis of the ammonia spectrum is more difficult due to the corrosive nature of this gas. Furthermore ammonia at the pressures and cold temperatures found in the gas giant atmospheres is close to condensation. However there is increased interest in the spectroscopy of ammonia as a result of the success of the Galileo mission, and we present here measurements and analysis of ammonia transmission spectra originally measured in 1984 but never previously published until now. These data have been fitted with band models and k-distribution models and we present the results of both these analyses. The data set uniquely covers the near-infrared range vital for the analysis of data from the Galileo near-infrared mapping spectrometer (NIMS) instrument and hence until further measurements can be made, these are the best and only data that exist to analyse ammonia in the near infrared spectra of the gaseous planets.

Infrared band strengths of HFC-134a vapour

Abstract Infrared absorbance cross sections and integrated band strengths for HFC-134a (1-fluoro,2-trifluoroethane, CFH2CF3) vapour have been determined at six temperatures (203, 213, 233, 253, 273, and 294 K) for the region 600–1600 cm−1 using Fourier transform infrared spectroscopy. Air-broadened spectra of HFC-134a vapour have been recorded at 203, 253, and 294 K using mixtures containing 5, 20, and 100 kPa dry air. Spectroscopic resolution was 0.03 cm−1, with additional high resolution (0.003 cm−1) measurements of the pure vapour at 294 K.