Derivation of Optical Properties of Carbonaceous Aerosols by Monochromated Electron Energy-Loss Spectroscopy
Derivation of Optical Properties of Carbonaceous Aerosols by Monochromated Electron Energy-Loss Spectroscopy
复制标题
通过单色电子能量损失光谱推导碳质气溶胶的光学性质
DOI：
10.1017/s143192761400049x
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发表时间：
2013
影响因子：
2.8
通讯作者：
James R. Anderson
中科院分区：
文献类型：
--
作者：
Jiangtao Zhu;P. Crozier;P. Ercius;James R. Anderson
摘要 单色电子能量损失光谱（EELS）用于测定碳质气溶胶从红外到紫外光谱区域的光学特性。确定它们的光学特性对于了解它们对气候变化辐射强迫的准确贡献至关重要。讨论了表面和界面等离子体激元效应对 EELS 确定的介电数据准确性的影响。我们的测量表明，Kramers−Kronig 分析的标准薄膜公式可用于精确测定尺寸小至约 40 nm 的碳质颗粒的介电函数。大气中发现的石墨和无定形碳球的复折射率是在 200-1,200 nm 的波长范围内测定的。石墨碳具有较强的吸收性黑碳，而无定形碳表现出较弱的吸收性棕碳特征。 EELS 方法为探索大气碳光学特性的变化提供了重要工具。
Abstract Monochromated electron energy-loss spectroscopy (EELS) is employed to determine the optical properties of carbonaceous aerosols from the infrared to the ultraviolet region of the spectrum. It is essential to determine their optical properties to understand their accurate contribution to radiative forcing for climate change. The influence of surface and interface plasmon effects on the accuracy of dielectric data determined from EELS is discussed. Our measurements show that the standard thin film formulation of Kramers−Kronig analysis can be employed to make accurate determination of the dielectric function for carbonaceous particles down to about 40 nm in size. The complex refractive indices of graphitic and amorphous carbon spherules found in the atmosphere were determined over the wavelength range 200–1,200 nm. The graphitic carbon was strongly absorbing black carbon, whereas the amorphous carbon shows a more weakly absorbing brown carbon profile. The EELS approach provides an important tool for exploring the variation in optical properties of atmospheric carbon.