We have recorded spectra of iron-neon and iron-argon hollow cathode lamps in the region 1700Å -5 µm (59 000 -2000 cm −1 ), with Fourier transform (FT) spectrometers at the National Solar Observatory, Tucson, Arizona, U.S.A. and Imperial College, London, U.K., and with a high resolution grating spectrograph at the National Institute of Standards and Technology, Gaithersburg, U.S.A. The uncertainty of the strongest lines in the FT spectra is <0.002 cm −1 (0.2 mÅ at 3000Å; 8 mÅ at 2 µm ). Pressure and current-dependent shifts are <0.001 cm −1 for transitions between low lying levels, increasing to 0.006 cm −1 for transitions between the most highly excited levels. We report 28 new energy levels of Fe I and revised values of another 818 levels. We have identified 9501 lines as due to 9759 transitions in Fe I, and these are presented in the form of a new multiplet table and finding list. This compares with the ∼5500 lines due to 467 energy levels in the multiplet tables of Moore (1950, 1959). The biggest increase is in the near ultraviolet and near infra-red, and many of the new lines are present in the solar spectrum. Experimental log(gf) values are included where they are available. A further 125 unidentified lines due to Fe I are given. The tables are also available in computer-readable form.

We use time-resolved laser-induced fluorescence to measure the lifetime of 186 Fe levels with energies between 25 900 and 60 758 cm . Measured emission branching fractions for these levels yield transition probabilities for 1174 transitions in the range 225-2666 nm. We find another 640 Fe transition probabilities by interpolating level populations in the inductively coupled plasma spectral source. We demonstrate the reliability of the interpolation method by comparing our transition probabilities with absorption oscillator strengths measured by the Oxford group [Blackwell et al., Mon. Not. R. Astron. Soc. 201, 595-602 (1982)]. We derive precise Fe level energies to support the automated method that is used to identify transitions in our spectra.

Abstract. The importance of nitrogen dioxide in both the troposphere and the stratosphere has been known for some years, and since the early 1970s, spectroscopic determinations have played an important role in understanding NOx chemistry. Spectroscopic measurements of the atmosphere have improved in quality in recent years to the point that an accurate determination of the NO 2 absorption cross section is essential to accurate retrievals of not only NO 2 but also less abundant species in the troposphere and stratosphere. NO2 is such a large absorber (approximately 1% at large air mass) in the stratosphere at twilight or in the troposphere under even mildly polluted conditions, that if it is not properly removed from observed spectra, the spectra of the more subtle species are masked and cannot be measured at all. We present cross sections of NO2 in the spectral region 350-585 nm at four temperatures between 217 and 298 K and total pressures between 100 and 600 torr at a mixing ratio of 84.1 ppmv and at a spectral resolution sufficient for accurate convolution with instruments typically used to measure atmospheric NO 2. Data will be presented to demonstrate the presence of NO 2 pressure dependence in high resolution. A detailed comparison with commonly used literature cross sections is made to show how such instrument parameters as wavelength accuracy, resolution, spectrograph scattered light, and data sampling affect the usefulness of the observed cross section.

The infrared spectrum of the hydroxyl radical OH, between 1850 and 9000 cm-1 , has been measured with a Fourier transform spectrometer. The source, a hydrogen-ozone diffusion flame, was designed to study the excitation of rotation-vibration levels of the OH Meinel bands under conditions similar to those in the upper atmosphere which produce the nighttime OH airglow emission. Twenty-three bands were observed: nine bands in the Ap = 1 sequence, nine bands in the Ap = 2 sequence, and five bands in the Ap = 3 sequence. A global nonlinear least-squares fit of 1696 lines yielded molecular parameters with a standard deviation of0.003 cm-1. Term values are computed, and transition frequencies in the Ap = 3, 4, 5, 6 sequences in the near-infrared are predicted. Subject headings: laboratory spectra-molecular processes 351

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