Retrieval of dust-particle refractive index using the phenomenon of negative polarization

•We study the phenomenon of negative polarization in irregularly shaped particles.•The location of the polarization minimum is unambiguously dependent on Re(m).•The negative-polarization amplitude varies non-monotonically through Im(m)=0-0.02.•The amplitude of negative polarization quickly decays through Im(m)=0.02-0.1.•We estimate m≈(1.68-1.83)+(0.01-0.02)i in the Allende meteorite at λ=0.633 μm.

We study the phenomenon of negative polarization in irregularly shaped agglomerated debris particles. We find that the location of the negative polarization minimum is unambiguously governed by Re(m). Furthermore, the amplitude of the negative polarization puts a strong constraint on the material absorption in target particles regardless of their real part of refractive index Re(m). The interrelation can be parameterized with a simple formula and it can be utilized in remote sensing. We apply our finding to laboratory optical measurements of Allende meteorite at λ=0.633 μm and estimate its complex refractive index to be m≈(1.68-1.83)+(0.01-0.02)i.