Craig J. Sansonetti

Wavelengths of spectral lines in mercury pencil lamps.

The wavelengths of 19 spectral lines in the region 253-579 nm emitted by Hg pencil-type lamps were measured by Fourier-transform spectroscopy. Precise calibration of the spectra was obtained with wavelengths of (198)Hg as external standards. Our recommended values should be useful aswavelength-calibration standards for moderate-resolution spectrometers at an uncertainty level of 0.0001 nm.

The Spectrum of Th-Ar Hollow Cathode Lamps in the 691-5804 nm region: Establishing Wavelength Standards for the Calibration of Infrared Spectrographs

We report new observations of the infrared (IR) spectrum of low-current Th-Ar hollow cathode lamps with the 2 m Fourier transform spectrometer (FTS) at the National Institute of Standards and Technology. These observations establish more than 2400 lines that are suitable for use as wavelength standards in the range 900Y4500 nm. The line list is used as input for a physical instrument model that provides the wavelength calibration for the Cryogenic HighResolutionIREchelleSpectrometer(CRIRES),theEuropeanSouthernObservatory’snewhigh-resolution(R � 100;000) IRspectrographattheVeryLargeTelescope.Wehavealsoobservedthevariationof thespectrumof Th-Arlampsasa function of operating current. The results allow us to optimize the spectral output in terms of relative intensity and linedensityforoperationonthetelescope.OurresultsshouldbegenerallyusefulforwavelengthcalibrationinnearIR astronomy, providing a high density of sharp, well-characterized emission lines with the ease and efficiency of operation of a commercial discharge lamp. Subject headingg atomic data — catalogs — instrumentation: spectrographs — methods: laboratory — standards — techniques: spectroscopic

Mercury in the HgMn stars chi Lupi and HR 7775

Observations of mercury lines in the HgMn stars chi Lupi and HR 7775 made with the Hubble Space Telescope Goddard High Resolution Spectrograph are presented and analyzed. In chi Lupi we find that all observed lines are consistent with the same isotopic mixture (essentially pure (204)Hg). Strong ionization anomalies are present, with UV Hg I lines being too weak and Hg III lines too strong for the abundance derived from lines of the majority ionization state, Hg rr. Observations of mercury in I;IR 7775 show less extreme isotope and ionization anomalies. We find that the ionization anomaly in the Hg I resonance lines can be plausibly explained as a non-LTE effect, but the same non-LTE calculations show that the Hg III ionization anomaly in chi Lupi cannot be explained in this way. Radiative force calculations show that the observed mercury abundance cannot be supported in the atmosphere by the radiative forces alone. We suggest that weak mixing brings mercury into the line-forming region from below the photosphere, while a wind of order 10(-14) M. yr(-1) supports a cloud of Hg III at very small optical depths. (Less)

Atlas of the spectrum of a platinum/neon hollow-cathode reference lamp in the region 1130-4330 Å

The spectrum of a platinum hollow-cathode lamp containing neon carrier gas was recorded photographically and photoelectrically with a 10.7 m normal-incidence vacuum spectrograph. Wavelengths and intensities were determined for about 5600 lines in the region 1130–4330 Å. An atlas of the spectrum is given, with the spectral lines marked and their intensities, wavelengths, and classifications listed. Lines of impurity species are also identified. The uncertainty of the photographically measured wavelengths is estimated to be ± 0.0020 Å. The uncertainty of lines measured in the photoelectric scans is 0.01 Å for wavelengths shorter than 2030 Å and 0.02 Å for longer wavelengths. Ritz-type wavelengths are given for many of the classified lines of Pt II with uncertainties varying from ±0.0004 to ± 0.0025 Å. The uncertainty of the relative intensities is estimated to be about 20%.

Irradiances of spectral lines in mercury pencil lamps.

The irradiancesof 37 spectral lines emitted bymercury pencil-type lamps were measuredby comparison with calibrated continuum sources. The lines span the region 230-590 nm. For the 14 most prominent lines the absolute irradiances should be useful for radiometric calibrations at an uncertainty level of ~15% 195% confidence2. The ratios of the irradiances for this same group of lines are significantly more reproducible; they should be useful at an uncertainty level of ~10%.

Wavelengths and intensities of a platinum/neon hollow cathode lamp in the region 1100-4000 A

The spectrum of a platinum hollow cathode lamp containing neon carrier gas was recorded photographically and photoelectrically with a 10.7 m normal-incidence vacuum spectrograph. Wavelengths and intensities were determined for about 3000 lines in the region 1100-4000 A. The uncertainty of the measured wavelengths is estimated to be + or - 0.0020 A. Ritz-type wavelengths are given for about 550 classified lines of Pt II with uncertainites varying from + or - 0.0004 A to + or - 0.0025 A. The uncertainty of the relative intensities is estimated to be about 20 percent.

Wavelengths, Energy Level Classifications, and Energy Levels for the Spectrum of Neutral Neon

We have prepared a comprehensive critically evaluated compilation of the most accurate wavelength measurements for classified lines of neutral neon (Ne I) in its natural isotopic abundance. Data from 19 sources spanning the region 256 A to 54 931 A are included. Based on this line list we have derived optimized values for the energy levels of neutral neon. Tabular data for 1595 classified lines and 374 energy levels are provided. In addition to the observed wavelengths, we present revised wavelengths calculated from the optimized energy levels for all lines that have been previously recommended for use as secondary wavelength standards.

Reference lines for dye-laser wave-number calibration in the optogalvanic spectra of uranium and thorium

The optogalvanic spectra of uranium and thorium observed in commercial hollow-cathode lamps provide convenient lines for dye-laser wave-number calibration. We describe a simple procedure by which a single-frequency cw dye laser can be set on such lines with an accuracy of a few parts in 108. We report wave numbers for 16 U and 16 Th lines distributed over the wavelength range 5750–6920 A. The estimated uncertainty of the measurements is 0.0003 cm−1 for U and 0.0004 cm−1 for Th. The results are compared with previous U and Th measurements and are found to be in good agreement with recently reported emission wave numbers determined by Fourier spectroscopy.

Absolute Wavelength Determinations in Molecular Tellurium: New Reference Lines for Precision Laser Spectroscopy

We have observed the spectrum of 130Te2 in the range 4712–5020 A by using Doppler-free frequency-modulation spectroscopy. The wave numbers of 32 selected lines have been measured interferometrically with an accuracy of 2.2 parts in 109. These measurements provide a well-distributed set of precise reference lines for this region. Good agreement is found with four lines that were previously measured in other laboratories for use as transfer standards in the spectroscopy of hydrogen, deuterium, positronium, and muonium.

The Bismuth Abundance in the HGMN Stars chi Lupi and HR 7775 and Improved Atomic Data for Selected Transitions of BI I, BI II, and BI III

High-resolution spectra of the chemically peculiar HgMn stars chi Lupiand HR 7775, obtained with the Hubble Space Telescope/Goddard HighResolution Spectrograph, are investigated for their abundance of bismuthby comparison with LTE synthetic spectrum modeling. HR 7775, previouslyknown from International Ultraviolet Explorer spectra to display stronglines of Bi II, is determined to have bismuth present at an enhancementlevel of nearly 5 orders of magnitude from the lines Bi IIlambdalambda1436, 1902 and Bi III lambda1423. The bismuthenhancement for chi Lupi is found to be near a level of 1.5 dex, andan ionization anomaly between Bi+ and Bi++ isapparent. HR 7775 abundance enhancements of the heavy elements platinum,[Pt/H]=4.7 dex, and gold, [Au/H]=3.8 dex, have also been determined. Newlaboratory measurements for wavelengths and hyperfine structure patternsof Bi I/Bi II/Bi III lines are presented, as well as the results ofcalculations for hyperfine structure constants and oscillator strengthsfor selected lines of Bi II and Bi III. Based on observations with theNASA/ESA Hubble Space Telescope, obtained at the Space Telescope ScienceInstitute, which is operated by the Association of Universities forResearch in Astronomy, Inc., under NASA contract NAS5-26555. (Less)