Physics Seminar - Electronic spectroscopy of MH molecules a contribution to laboratory astrophysics-FR

Event Details:

Amanda Ross, CNRS research scientist at Institut Lumière Matière, Unité Mixte de Recherche UMR 5306 (U. Lyon 1 & CNRS), Université de Lyon, France will present "Electronic spectroscopy of MH molecules : a contribution to laboratory astrophysics."

Harrison McCain visiting scientist at UNB April-July 2017

Abstract: Spectroscopy – in whatever form – is still our only probe for distant objects where direct investigation is impossible. Molecular spectra have been identified in cool stellar objects (where cool implies temperatures around 3000 K). Some transition metal monohydrides have been identified in sunspots and in the spectra of cool stars [1], FeH and CrH raising special interest because they are good probes of magnetic field [2]. Laboratory spectra are required to supply reliable parameters for spectropolarimetric analysis of such remote objects, and this talk focuses in this direction. One obvious hurdle arises from the equilibrium temperatures of 'cool' stellar objects, far higher than the range of temperatures typically accessible in the laboratory, particularly when high spectral resolution is required. Another is the difficulty in modelling the electronic structure of these species, characterised by non-zero spin and orbital angular momentum, and large spin-orbit couplings between them. I will illustrate some of our work in this area with spectra of FeH and NiH formed in a hollow-cathode sputtering source [3]. We have used cw laser excitation and Fourier-transform resolved fluorescence to study Zeeman patterns, working at magnetic fields between 0.3 and 0.9 Tesla provided by permanent magnets, and have used parameters determined in the laboratory to investigate the profiles of FeH lines observed in sunspot spectra, recorded in Stokes V polarisation at the solar Telescope THEMIS in Tenerife [4]. We find that the field deduced from atomic lines (Ti,Fe) is around ~10 % higher than that found from FeH, compatible with molecules forming at higher altitudes in the solar atmosphere.

[1] L. Wallace, W. Livingston, P. Bernath, and R.S. Ram, N.S.O. Technical Report N° 1998-002, Available online : ftp://nsokp.nso.edu/pub/atlas/spot3alt (1998).

[2] N. Afram, S.V. Berdyugina, D.M. Fluri, S.K. Solanki , and A. Lagg, Astron. & Astrophys.  482 (2), 387 (2008).

[3] A.J. Ross, P. Crozet, C. Richard, H. Harker, S.H. Ashworth, and D.W. Tokaryk, Molecular Physics  110, 2019 (2012).

[4] P. Crozet, G. Tourasse, A.J. Ross, F. Paletou, and A. Lopez Ariste, Proceedings, 1st European Conference on Laboratory Astrophysics (ECLA)  58, 63 (2012).

Building: IUC Physics

Room Number: 204