Seminar: Laboratory Infrared Atomic Spectroscopy for Astrophysics

Analyses of astronomical spectra rely on detailed knowledge of the structure of the atomic species involved. Furthermore, the line strengths must be accurately known to use astronomical spectra for quantitative analyses, such as determination of stellar and nebular temperature, density or chemical abundance. Elemental presence in kilonova or exoplanet spectra depend on more extensive atomic linelists.

The optical region is well studied, but elements still miss important transitions. The near-infrared wavelength region, 1-5 microns, is important thanks to its smaller interstellar extinction, and several spectrographs are matching these e.g. the CRIRES+ at VLT and the APOGEE survey. The planned E-ELT will also observe in the infrared domain. A major problem with the infrared region is the severe lack of atomic data.

Our research program on Laboratory Atomic Astrophysics focuses on meeting the needs for atomic data; both line identification and measurements of intrinsic line strengths, the oscillator strengths. This includes high-accuracy data for a few transitions, as well as the need for complete linelists for other studies.

We use the branching fraction and lifetime technique to measure line strengths, using the high-resolution Fourier spectrometer in combination with radiative lifetimes. The measurements are combined with calculations using the GRASP and ATSP2k codes, providing a high-accuracy data set for astrophysical analysis. We participate in observational programs to define the interesting problems and priorities in need for atomic data.

I will discuss optical and infrared transitions in the view of atomic structure, and a base for the astronomical analysis as well as for laboratory and theoretical priorities. I will present the laboratory technique used to derive improved data.

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There will be fika after the seminar.