Description:
<jats:title>Abstract</jats:title>
<jats:p>We study the circular polarization of the magnetic-field-induced transition (MIT) between the 3<jats:italic>d</jats:italic>
<jats:sup>5</jats:sup>(<jats:sup>6</jats:sup>
<jats:italic>S</jats:italic>)4<jats:italic>d</jats:italic>
<jats:sup>7</jats:sup>
<jats:italic>D</jats:italic>
<jats:sub>2</jats:sub> and 3<jats:italic>d</jats:italic>
<jats:sup>5</jats:sup>(<jats:sup>6</jats:sup>
<jats:italic>S</jats:italic>)4<jats:italic>p</jats:italic>
<jats:sup>7</jats:sup>
<jats:italic>P</jats:italic>
<jats:sub>4</jats:sub>° states of Cr <jats:sc>i</jats:sc> at 533.03 nm (wavelength in air). The fractional circular polarization <jats:italic>V</jats:italic>/<jats:italic>I</jats:italic> of this spectral line resulting from the solution of the radiation transfer problem in a sunspot model permeated by a homogeneous magnetic field of 3 kG shows amplitudes of about 2%. Spectropolarimetric observations of two sunspots were obtained with the Zurich Imaging Polarimeter-3 at the Istituto ricerche solari Aldo e Cele Daccò observatory in Locarno, Switzerland. The observed <jats:italic>V</jats:italic>/<jats:italic>I</jats:italic> profiles show approximately antisymmetrical shapes with an amplitude of around 0.1% and 0.2% for the two sunspots. The center of this profile coincides with the wavelengths predicted for the abovementioned MIT. We apply an inversion code to the spectropolarimetric data of the Cr <jats:sc>i</jats:sc>-permitted lines at 532.91 and 532.98 nm, as well as to the MIT line at 533.03 nm, to infer a stratification of the emitting atmosphere. We compare the <jats:italic>V</jats:italic>/<jats:italic>I</jats:italic> profiles synthesized in the inferred atmosphere models with the observations, showing that the observed signal likely corresponds to the MIT line.</jats:p>