New Insights on the Collisional Depolarization of the Second Solar Spectrum of the Sr i 4607 Å Line

Abstract

Abstract The spectrum of the linear polarization generated by scattering of anisotropic radiation near to the limb is called second solar spectrum (SSS). Our purpose is to present a new approach that allows accurate determination of the collisional depolarization rate D 2 of the SSS of the Sr i 4607 Å line. Most of the inaccuracy in determining the depolarization rate arises from errors in obtaining the interaction potential between the Sr i and H i atoms. To improve the accuracy of the depolarization rate, we determine hybrid potentials based on (1) ab initio quantum chemistry potentials for small interatomic distances; (2) Rayleigh–Schrödinger–Unsöld (RSU) potentials for large interatomic distances; and (3) joining the RSU and ab initio potentials by reasonably accurate interpolation to describe the interaction in the intermediate interatomic distances. The obtained hybrid potentials are used to infer new accurate hybrid depolarization rate for solar applications. Interestingly, we show that values of the hybrid rates are remarkably stable under the variation of the methods employed to compute hybrid potentials. Expected percentage of imprecision on the solar magnetic value resulting from a hypothetical inaccuracy in the D 2 is evaluated.