Faculty of Science and Technology, Norwegian University of Life Sciences, Aas, Norway.
Department of Physics, Wesleyan University, Middletown, Connecticut, USA.
Sci Rep. 2021 Feb 25;11(1):4675. doi: 10.1038/s41598-021-84064-5.
Mie-type scattering features such as ripples (i.e., sharp shape-resonance peaks) and wiggles (i.e., broad oscillations), are frequently-observed scattering phenomena in infrared microspectroscopy of cells and tissues. They appear in general when the wavelength of electromagnetic radiation is of the same order as the size of the scatterer. By use of approximations to the Mie solutions for spheres, iterative algorithms have been developed to retrieve pure absorbance spectra. However, the question remains to what extent the Mie solutions, and approximations thereof, describe the extinction efficiency in practical situations where the shapes of scatterers deviate considerably from spheres. The aim of the current study is to investigate how deviations from a spherical scatterer can change the extinction properties of the scatterer in the context of chaos in wave systems. For this purpose, we investigate a chaotic scatterer and compare it with an elliptically shaped scatterer, which exhibits only regular scattering. We find that chaotic scattering has an accelerating effect on the disappearance of Mie ripples. We further show that the presence of absorption and the high numerical aperture of infrared microscopes does not explain the absence of ripples in most measurements of biological samples.
米氏散射特征，如波纹（即尖锐的形状共振峰）和摆动（即宽的振荡），是细胞和组织的红外微光谱中经常观察到的散射现象。当电磁辐射的波长与散射体的大小相当时，通常会出现这些现象。通过对球体米氏解的近似，已经开发出迭代算法来提取纯吸收光谱。然而，问题仍然存在，即在散射体的形状与球体有很大偏差的实际情况下，米氏解及其近似在多大程度上可以描述消光效率。本研究的目的是研究在波系统混沌的情况下，偏离球形散射体如何改变散射体的消光特性。为此，我们研究了一个混沌散射体，并将其与仅表现出规则散射的椭圆形散射体进行了比较。我们发现，混沌散射对米氏波纹的消失有加速作用。我们进一步表明，吸收的存在和红外显微镜的高数值孔径并不能解释为什么在大多数生物样本的测量中没有出现波纹。
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