Florence Concepcion
Gather.town id
CCE21
Poster Title
New Accurate Atomic Data for Astrophysical Applications
Institution
Imperial College London
Abstract (short summary)
Modern observations of astrophysical spectra are in many cases of higher quality than those observed within a laboratory setting. This can result in inaccurate conclusions being drawn. Accurate measurements of spectral line wavelengths and oscillator strengths are required particularly for use in stellar models and chemical abundance calculations, and in surveys such as Gaia-ESO or APOGEE and future surveys. Laboratory astrophysicists aim to measure and improve the atomic data most useful for astronomers, for light and heavy elements across the spectrum, from IR to vacuum-UV (VUV).
Atomic data of iron-group elements are important due to their high abundance and line-rich spectra. Lanthanides are under study as their line-rich spectra overwhelms at sites of r-process production. Our high-resolution Fourier Transform Spectrometry (FTS) group at Imperial College London has, supported by STFC, been providing accurate atomic data for use in astrophysics.
Recent results include new Fe I oscillator strengths for use in Galactic surveys (Belmonte et al. 2017), and 1130 wavelengths and transition probabilities of parity-forbidden Lines for Mn II (Liggins et al. 2021). The first high-resolution measurements of UV transition wavelengths of Cr III are being used as wavelength standards (Smillie et al. 2008). There has been an order of magnitude improvement in atomic data for Co III (Smillie et al. 2016) and in the accuracy of energy levels and transition wavelengths for Mn II (Liggins et al. 2021) and Ni II (Clear, PhD, Imperial College, 2018). Analysis of hyperfine structure of Co II lines has led to the determination of A constants for 292 levels (Ding and Pickering, 2020).
Using new spectra recorded, analysis is underway for accurate wavelengths and atomic energy levels in Mn I and Fe III. The investigation into the spectrum of Neodymium, with a focus on Nd III, has also begun. We welcome data requests!
Atomic data of iron-group elements are important due to their high abundance and line-rich spectra. Lanthanides are under study as their line-rich spectra overwhelms at sites of r-process production. Our high-resolution Fourier Transform Spectrometry (FTS) group at Imperial College London has, supported by STFC, been providing accurate atomic data for use in astrophysics.
Recent results include new Fe I oscillator strengths for use in Galactic surveys (Belmonte et al. 2017), and 1130 wavelengths and transition probabilities of parity-forbidden Lines for Mn II (Liggins et al. 2021). The first high-resolution measurements of UV transition wavelengths of Cr III are being used as wavelength standards (Smillie et al. 2008). There has been an order of magnitude improvement in atomic data for Co III (Smillie et al. 2016) and in the accuracy of energy levels and transition wavelengths for Mn II (Liggins et al. 2021) and Ni II (Clear, PhD, Imperial College, 2018). Analysis of hyperfine structure of Co II lines has led to the determination of A constants for 292 levels (Ding and Pickering, 2020).
Using new spectra recorded, analysis is underway for accurate wavelengths and atomic energy levels in Mn I and Fe III. The investigation into the spectrum of Neodymium, with a focus on Nd III, has also begun. We welcome data requests!
Plain text (extended) Summary
Modern observations of astrophysical spectra are in many cases of higher quality than those observed within a laboratory setting. This can result in inaccurate conclusions being drawn. Accurate measurements of spectral line wavelengths and oscillator strengths are required particularly for use in stellar models and chemical abundance calculations, and in surveys such as Gaia-ESO Survey or APOGEE. Atomic data has also been used to better analyse quasar spectra, to constrain space-time variations in the fine structure constant.
We are laboratory astrophysicists that aim to measure and improve the atomic data most useful for astronomers, from IR to vacuum-UV. We are currently working on improving atomic data of iron-group elements which are important due to their high abundance and line-rich spectra, accounting for the majority of opacity in stars. Lanthanides are also under study as their line-rich spectra are present in chemically peculiar stars and overwhelm at sites of r-process production.
Our high-resolution Fourier Transform Spectrometry (FTS) group at Imperial College London has been providing accurate atomic data for use in astrophysics, with at least an order of magnitude improvement over previously measured data. The FTS spectral range is 140 - 800 nm with a resolving power of 2 million at 200 nm. Beyond this spectral range, we supplement our measurements with infrared FT spectra recorded at NIST (USA) and Lund University (Sweden), and vacuum ultraviolet Grating spectra recorded at NIST (in collaboration with G. Nave).
We use our accurate FTS measured wavelengths to improve energy levels with uncertainties up to 0.001 cm-1 and to search for unknown energy levels. Wavelength accuracy improvement of our FTS measured Co III showed that the inaccuracies of the past grating data exceed the stated uncertainty of 10 mÅ.
Accurate Hyperfine structure (HFS) data are vital for chemical abundance determinations and line identification. Spectral lines may be broadened due to hyperfine components but can easily be interpreted as many other blended lines. By fitting FTS spectral lines, measurements of magnetic dipole hyperfine interaction A constants can be made. In Co II, over 700 spectral lines were fit, leading to the determination of A constants for 292 levels. This increased the number of Co II levels with known A values tenfold!
Other recent results include new Fe I oscillator strengths for use in Galactic surveys and 1130 wavelengths and transition probabilities of parity-forbidden Lines for Mn II. The first high-resolution measurements of UV transition wavelengths of Cr III are being used as wavelength standards. There has been an order of magnitude improvement in accuracy of energy levels and transition wavelengths for Co III, Mn II and Ni II.
Using new spectra recorded, analysis is underway for accurate wavelengths and atomic energy levels in Mn I, Fe III, Nd II and Nd III.
We welcome data requests! Please contact us with any specific data needs as we are developing a defined list of anticipated needs.
We are laboratory astrophysicists that aim to measure and improve the atomic data most useful for astronomers, from IR to vacuum-UV. We are currently working on improving atomic data of iron-group elements which are important due to their high abundance and line-rich spectra, accounting for the majority of opacity in stars. Lanthanides are also under study as their line-rich spectra are present in chemically peculiar stars and overwhelm at sites of r-process production.
Our high-resolution Fourier Transform Spectrometry (FTS) group at Imperial College London has been providing accurate atomic data for use in astrophysics, with at least an order of magnitude improvement over previously measured data. The FTS spectral range is 140 - 800 nm with a resolving power of 2 million at 200 nm. Beyond this spectral range, we supplement our measurements with infrared FT spectra recorded at NIST (USA) and Lund University (Sweden), and vacuum ultraviolet Grating spectra recorded at NIST (in collaboration with G. Nave).
We use our accurate FTS measured wavelengths to improve energy levels with uncertainties up to 0.001 cm-1 and to search for unknown energy levels. Wavelength accuracy improvement of our FTS measured Co III showed that the inaccuracies of the past grating data exceed the stated uncertainty of 10 mÅ.
Accurate Hyperfine structure (HFS) data are vital for chemical abundance determinations and line identification. Spectral lines may be broadened due to hyperfine components but can easily be interpreted as many other blended lines. By fitting FTS spectral lines, measurements of magnetic dipole hyperfine interaction A constants can be made. In Co II, over 700 spectral lines were fit, leading to the determination of A constants for 292 levels. This increased the number of Co II levels with known A values tenfold!
Other recent results include new Fe I oscillator strengths for use in Galactic surveys and 1130 wavelengths and transition probabilities of parity-forbidden Lines for Mn II. The first high-resolution measurements of UV transition wavelengths of Cr III are being used as wavelength standards. There has been an order of magnitude improvement in accuracy of energy levels and transition wavelengths for Co III, Mn II and Ni II.
Using new spectra recorded, analysis is underway for accurate wavelengths and atomic energy levels in Mn I, Fe III, Nd II and Nd III.
We welcome data requests! Please contact us with any specific data needs as we are developing a defined list of anticipated needs.
URL
f.concepcion17@imperial.ac.uk
Poster file