|Sansonetti, Craig Joseph
Space-based telescopes such as the Hubble Space Telescope have provided spectra with unprecedented detail and accuracy for a wide variety of astrophysical objects. Modern ground-based telescopes are equipped with spectrographs that can provide the high wavelength accuracy and sensitivity required for exoplanet detection and the study of possible time-variation of the fundamental constants in the early Universe. Data from these instruments extend from below 100 nm to the near infrared. For many elements, existing laboratory data are insufficient to permit the calibration and interpretation of the astrophysical spectra to the required accuracy. We are measuring and analyzing spectra of selected atoms and ions that have important astrophysical applications to obtain wavelengths, oscillator strengths, energy levels, isotope shifts, and hyperfine structures. Available facilities include 10.7-m normal and grazing incidence spectrographs, a 2-m visible/infrared Fourier-transform spectrometer (FTS), a vacuum ultraviolet FTS, and calibrated radiometric standard light sources. With quantitative radiometric techniques using phosphor storage image plates, we can now measure branching fractions and oscillator strengths for wavelengths as short as 110 nm, and we are working to extend these techniques to still shorter wavelengths.