Volume 382, Number 3, FebruaryII 2002
|Page(s)||L17 - L21|
|Published online||15 February 2002|
Letter to the Editor
Scattering polarization of molecular emission lines in the quiet solar chromosphere
Département Cassini, UMR 6529, Observatoire de la côte d'Azur, BP 4229, 06304 Nice, France
2 UMR 5572, Observatoire Midi-Pyrénées, 14 avenue Édouard Belin, 31400 Toulouse, France
Corresponding author: M. Faurobert, firstname.lastname@example.org
Accepted: 13 December 2001
We present scattering polarization measurements performed with THEMIS in July 2000 near the south polar limb. The low level of scattered light at THEMIS, which is the only large solar telescope to include a superpolished primary mirror, allows, in good seeing conditions, to observe the emission spectrum of the low chromosphere above the limb. These are, as far as we know, the first high spectral resolution observations of the intensity and the first measurements of the polarization of and molecular lines in emission above the limb. Molecules are present in a thin layer in the region of the temperature minimum between the photosphere and the chromosphere. We present a very simple model for the formation of the polarized lines and we relate the observed polarization rates to the so-called intrinsic line polarizability coefficients W2. Those quantities may be derived from quantum mechanical computations involving the solution of the Schrödinger equation for the molecular potential. Solar observations provide a direct way of checking these heavy computations and contribute to the improvement of our knowledge in molecular physics. Nine molecular transitions and two transitions are present in our spectral window; we find that for the transitions, the polarizability is between 0.13 and 0.26 and that it takes higher values, namely 0.41 and 0.46, for the two transitions.
Key words: techniques: polarimetric / techniques: spectroscopic / Sun: atmosphere / Sun: polarization / spectral lines: scattering
© ESO, 2002
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