Complex refractive index (RI) is an important parameter to determine the radiative effects of aerosol. It is governed by the physico-chemical properties of the aerosol. Scarcity in the detailed information of spectral RI of fine and coarse mode aerosol is challenging and limits our understanding of interaction between aerosol and incoming solar radiation. Marginal data about the RI of aerosol are available for the long-wave radiation that too spatially constrained. In the present study, spectral RIs of pure submicron particles (kaolinite and illite) and polluted particles (comprised of kaolinite, illite, anthropogenic hematite, black carbon (BC), ammonium nitrate and ammonium sulphate) have been modelled for the wavelength range 0.38–21.5 µm using volume mixing rule. Particle aged with anthropogenic hematite shows overall increase in the imaginary part of refractive index (k), with increasing concentration of anthropogenic hematite (range 0.10–1.48%). Maximum enhancement in the k value (0.02) observed at 0.38 µm, while minimum k value (0.001) found at 1.2 µm. The complex RIs of aerosol comprised of kaolinite, illite, hematite, BC, ammonium sulphate and ammonium nitrate show “k” values ranging from 0.01 to 0.08 for the wavelength range 0.38 to 1.2 µm, while the highest values of 1.5 were observed at wavelength 21.5 µm. Negligible effect was observed in absorption pattern of particle with varying concentration of BC and anthropogenic hematite at wavelength > 2.5 µm.

复折射率（RI）是确定气溶胶辐射效应的重要参数。它由气溶胶的物理化学性质决定。精细和粗糙模式气溶胶光谱 RI 的详细信息缺乏具有挑战性，并限制了我们对气溶胶与入射太阳辐射之间相互作用的理解。气溶胶 RI 的边际数据可用于空间受限的长波辐射。在本研究中，已对波长范围 0.38– 21.5 µm 使用体积混合规则。k），随着人为赤铁矿浓度的增加（范围 0.10-1.48%）。在 0.38 µm 处观察到的k值 (0.02)的最大增强，而在 1.2 µm 处发现的最小k值 (0.001)。由高岭石、伊利石、赤铁矿、BC、硫酸铵和硝酸铵组成的气溶胶复合 RI 在 0.38 至 1.2 µm 波长范围内显示“ k ”值范围为 0.01 至 0.08，而在波长 21.5 处观察到的最高值为 1.5微米。在波长 > 2.5 µm 处不同浓度的 BC 和人为赤铁矿的颗粒吸收模式中观察到的影响可以忽略不计。