Modelling the optical and radiative properties of atmospheric particles are governed by one of the key input parameters i.e. refractive index of aerosols. Availability of the region-specific refractive index data of aerosol is major challenge for atmospheric community. The complex refractive index of aerosol is function of their physico-chemical properties. Uncertainty in the computation of the spectral refractive indices of the aerosol leads to erroneous assessment of their optical and radiative properties.

Refractive index of pure clay (Kaolinite and Illite) and polluted clay [Kaolinite, Illite, anthropogenic hematite, AH (0.10 to 1.48%), black carbon, BC (2 to 10%), ammonium sulphate, AS (13%) and ammonium nitrate, AN (8%)] submicron particle have been computed for the wavelength range 0.38 to 21.5 µm. Anthropogenic hematite enhanced the overall absorption in the UV and Visible range with maximum absorption upto 0.55 µm wavelength. Aging of the pure submicron clay particles with pollutants (AH, BC, AS, AN) significantly enhanced the imaginary part of the refractive index (k) in near infrared window (0.86 to 21.5 µm) of the solar radiation. Mixture of 1.48% AH and 10% BC shows maximum absorption in the UV, Visible and NIR region. Highest “k”value (1.2) was observed corresponding to 21.5 µm wavelength. The detailed insights of the study will be talked during the conference.