Accurate transition rates for the 5p - 5s transitions in Kr I

Branching fractions were measured for electric dipole transitions from the 5p upper levels to the 5s levels in neutral krypton atoms. The measurements were made with a wall-stabilized electric arc and a 2m monochromator for the spectral lines in the visible, and with a hollow cathode lamp and the NIST 2m-Fourier transform spectrometer for the lines in the near infrared. A semi-empirical calculation, based on accurately known lifetimes for six upper levels, was used to calculate lifetimes for which accurate measurements do not exist. This resulted in a complete set of lifetimes for all 5p levels. Branching fractions and lifetimes were used to calculate transition rates for the 5p-5s transitions. The relative uncertainties of the transition rates range from less than 1% for the strongest lines to about 10% for the weakest lines. Our data also reveal that most of the previous measurements appear to have been affected by opacity effects in the light sources.Comment: 18 pages, 6 figures, 5 table

The spectrum of Fe II

The spectrum of singly-ionized iron (Fe II) has been recorded using high-resolution Fourier transform and grating spectroscopy over the wavelength range 900 {\AA} to 5.5 {\mu}m. The spectra were observed in high-current continuous and pulsed hollow cathode discharges using Fourier transform (FT) spectrometers at the Kitt Peak National Observatory, Tucson, AZ and Imperial College, London and with the 10.7 m Normal Incidence Spectrograph at the National Institute of Standards and Technology. Roughly 12 900 lines were classified using 1027 energy levels of Fe II that were optimized to measured wavenumbers. The wavenumber uncertainties of lines in the FT spectra range from 10-4 cm-1 for strong lines around 4 {\mu}m to 0.05 cm-1 for weaker lines around 1500 {\AA}. The wavelength uncertainty of lines in the grating spectra is 0.005 {\AA}. The ionization energy of (130 655.4+-0.4) cm-1 was estimated from the 3d6(5D)5g and 3d6(5D)6h levels.Comment: 399 pages, 1 figure, 4 tables. Two large tables at end will appear online only in full journal article. Article accepted for publication in Astrophysical Journal Supplement Serie

Wavelengths of the 3d6(5D)4s a6D - 3d6(5D)4p y6P Multiplet of Fe II (UV 8)

We investigate the wavenumber scale of Fe I and Fe II lines using new spectra recorded with Fourier transform spectroscopy and using a re-analysis of archival spectra. We find that standards in Ar II, Mg I, Mg II and Ge I give a consistent wavenumber calibration. We use the recalibrated spectra to derive accurate wavelengths for the a6D-y6P multiplet of Fe II (UV 8) using both directly measured lines and Ritz wavelengths. Lines from this multiplet are important for astronomical tests of the invariance of the fine structure constant on a cosmological time scale. We recommend a wavelength of 1608.45081 {\AA} with a one standard deviation uncertainty of 0.00007 {\AA} for the a6D9/2-y6P7/2 transition.Comment: 29 pages, 7 figures, 8 tables. Accepted for publication in J. Opt. Soc. Am

Atomic Oscillator Strengths in the Vacuum Ultraviolet

We have developed techniques to measure branching fractions in the vacuum ultraviolet using diffraction grating spectroscopy and phosphor image plates as detectors. These techniques have been used to measure branching fractions in Fe II that give prominent emission lines in astrophysical objects

Development of a New, Precise Near-infrared Doppler Wavelength Reference: A Fiber Fabry-Perot Interferometer

We present the ongoing development of a commercially available Micron Optics fiber-Fabry Perot Interferometer as a precise, stable, easy to use, and economic spectrograph reference with the goal of achieving <1 m/s long term stability. Fiber Fabry-Perot interferometers (FFP) create interference patterns by combining light traversing different delay paths. The interference creates a rich spectrum of narrow emission lines, ideal for use as a precise Doppler reference. This fully photonic reference could easily be installed in existing NIR spectrographs, turning high resolution fiber-fed spectrographs into precise Doppler velocimeters. First light results on the Sloan Digital Sky Survey III (SDSS-III) Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectrograph and several tests of major support instruments are also presented. These instruments include a SuperK Photonics fiber supercontinuum laser source and precise temperature controller. A high resolution spectrum obtained using the NIST 2-m Fourier transform spectrometer (FTS) is also presented. We find our current temperature control precision of the FFP to be 0.15 mK, corresponding to a theoretical velocity stability of 35 cm/s due to temperature variations of the interferometer cavity.Comment: 16 pages, 11 figures. To appear in the proceedings of the SPIE 2012 Astronomical Instrumentation and Telescopes conferenc

The Infrared Spectrum of Uranium Hollow Cathode Lamps from 850 nm to 4000 nm: Wavenumbers and Line Identifications from Fourier Transform Spectra

We provide new measurements of wavenumbers and line identifications of 10 100 UI and UII near-infrared (NIR) emission lines between 2500 cm-1 and 12 000 cm-1 (4000 nm to 850 nm) using archival FTS spectra from the National Solar Observatory (NSO). This line list includes isolated uranium lines in the Y, J, H, K, and L bands (0.9 {\mu}m to 1.1 {\mu}m, 1.2 {\mu}m to 1.35 {\mu}m, 1.5 {\mu}m to 1.65 {\mu}m, 2.0 {\mu}m to 2.4 {\mu}m, and 3.0 {\mu}m to 4.0 {\mu}m, respectively), and provides six times as many calibration lines as thorium in the NIR spectral range. The line lists we provide enable inexpensive, commercially-available uranium hollow-cathode lamps to be used for high-precision wavelength calibration of existing and future high-resolution NIR spectrographs.Comment: 23 pages, 6 Figure