The optical constants of a liquid hydrocarbon such as liquid n-octane are basic material properties that may be used to evaluate their thermal radiation transfer capabilities. In this study, the ellipsometry method was used to measure the optical constants of liquid n-octane in the midinfrared wavelength range of 2.0–16.0 μm at temperatures of 20, 50, and 80°C. Experimental analyses indicate the significant effect of temperature on the refractive index, although it has little effect on the absorption index. With increasing temperature, the refractive index shows a linear decrease, and reduced density leads to weaker absorption intensities. The radiative properties of n-octane droplets, including the absorption and scattering efficiency factors of single droplets with droplet radii r = 10, 20, 50, and 100 μm and the absorption and scattering coefficients in a droplets-air system of droplet volume fractions f_v = 2%, 3%, and 4%, were calculated using Mie theory. The numerical results indicate that, with increasing temperature, the absorption efficiency factor slightly decreases, and the variation trend of the scattering efficiency factor is more complicated. With increasing droplet radius, the absorption efficiency factor increases within the studied wavelength range, except for certain absorption peaks, but the scattering efficiency factor tends to decrease. While the absorption is greater, the scattering is weaker for a given droplet radius. With an increasing volume fraction of n-octane droplets, the absorption and scattering coefficients increase linearly within the studied wavelength range.

中文翻译：

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液态正辛烷液滴在中红外区的光谱辐射特性

液态烃（例如液态正辛烷）的光学常数是基本的材料特性，可用于评估其热辐射传输能力。在这项研究中，使用椭圆偏光法测量液体正辛烷在中红外波长范围内的2.0-16.0光学常数 μ在20，50，和80℃的温度下米。实验分析表明温度对折射率有显着影响，尽管温度对吸收率影响很小。随着温度的升高，折射率呈线性下降，而密度降低导致吸收强度变弱。正辛烷液滴的辐射特性，包括具有液滴半径r的单个液滴的吸收和散射效率因子 分别为10、20、50和100μm，并且 液滴体积分数f _v在液滴-空气系统中的吸收系数和散射系数 使用Mie理论计算出= 2％，3％和4％。数值结果表明，随着温度的升高，吸收效率因数略有降低，散射效率因数的变化趋势更加复杂。随着液滴半径的增加，在所研究的波长范围内，吸收效率因数会增加，除了某些吸收峰外，但散射效率因数会降低。虽然吸收较大，但对于给定的液滴半径，散射较弱。随着正辛烷液滴体积分数的增加，在所研究的波长范围内，吸收系数和散射系数线性增加。