## 3 Results and Discussion  
### Distribution Mode  
Figure 4 shows the spectrum-averaged radiometric properties, including the extinction efficiency, absorption efficiency, scattering efficiency, and asymmetric parameter, varied with particle radius for particle aggregates of Mode A and Mode B with different minor components. In Mode A, the minor component particles are randomly positioned. The spectrum-averaged radiometric properties are averaged at wavelengths of 6.5-10 \(\upmu\)m.  
As seen in the figure, the curves for Mode A are different from those for Mode B, showing that the distribution of components does affect the radiometric properties to various extents. As for the absorption efficiency (Figure 4b), Mode A has lower values than Mode B when \(m_{2}=0.15+3.15\)i and \(m_{2}=1.46+2.75\)i. This shows that, when the minor component has a larger imaginary part of the refractive index or is more absorptive compared to the major component (\(m_{1}=1.6\)), concentrating the minor component in a few particles makes the particle aggregate less absorptive, and spreading the minor component into each particle makes the particle aggregate more absorptive. In addition, the absorption efficiency with \(m_{2}=1.46+2.75\)i is greater than that with \(m_{2}=0.15+3.15\)i for Mode A and Mode B. The absorption efficiency of Mode A is 60.3% lower than that of Mode B when \(m_{2}=1.46+2.75\)i and is 90.3% lower when \(m_{2}=0.15+3.15\)i. It should be noted that the absorption efficiency of a particle aggregate is mainly influenced by the imaginary part of the refractive index and that, when \(m_{2}=1.46+2.75\)i and \(m_{2}=0.15+3.15\)i, the imaginary part of the refractive index is significantly larger than it is when major component \(m_{1}=1.6\) (no adsorption). For Mode A, only the minor component particles contribute to absorption; however, for Mode B, all particles in the aggregate are absorptive, since the mixed material has a non-zero imaginary part of the refractive index, resulting in greater absorption efficiency than Mode A. Moreover, absorption grows exponentially with optical length [1; 52], and the particles in Mode B have a larger real part of the refractive index compared to the major component, and this increases the effective optical length in each particle and, therefore, makes the aggregate more absorptive. When \(m_{2}=3.102+0.0925\)i, the imaginary part nears that of the major component (which is zero), so the minor component is close to the major component in terms of absorption; under such a condition, the distribution of components becomes much less important to the absorption efficiency of the aggregate since both components are close in terms of absorption, so Mode A and Mode B become similar in terms of absorption efficiency, as evident by the relatively small difference of 8% between Mode A and Mode B. However, as the particle radius increases, the absorption efficiency between Mode A and Mode B changes: it decreases in Mode A and increases in Mode B. This may be attributed to the different distributions of the components between Mode A and Mode B. For the scattering efficiency (Figure 4c), Mode A has greater values compared to Mode B when \(m_{2}=0.15+3.15\)i or \(m_{2}=1.46+2.75\)i. This means, when the minor component has a large imaginary part of the refractive index, concentrating the minor component in a few particles causes more scattering in the aggregate compared to when it is evenly spread into each particle, indicating the important role that a few scattering particles play on the scattering efficiency of the aggregate. Scattering mostly occurs on the interface of the two chemical components [53]. In Mode B, the EMA method treated the two chemical components as evenly mixed and therefore artificially decreased the interface of the two chemical components such that scattering was reduced.