Simultaneous identification of optical constants and PSD of spherical particles by multi-wavelength scattering–transmittance measurement

2018 ◽  
Vol 413 ◽  
pp. 317-328 ◽  
Author(s):  
Jun-You Zhang ◽  
Hong Qi ◽  
Ya-Tao Ren ◽  
Li-Ming Ruan
Keyword(s):  
Optical Constants ◽  
Spherical Particles ◽  
Multi Wavelength ◽  
Simultaneous Identification

scholarly journals Elevated dust layers inhibit dissipation of heavy anthropogenic surface air pollution

2020 ◽  
Vol 20 (23) ◽  
pp. 14917-14932
Author(s):  
Zhuang Wang ◽  
Cheng Liu ◽  
Zhouqing Xie ◽  
Qihou Hu ◽  
Meinrat O. Andreae ◽  
...  
Keyword(s):  
Air Quality ◽  
North China ◽  
Spherical Particles ◽  
Trace Gas ◽  
Nonspherical Particles ◽  
Anthropogenic Aerosols ◽  
Haze Pollution ◽  
Multi Wavelength ◽  
Upper Level

Abstract. Persistent wintertime heavy haze incidents caused by anthropogenic aerosols have repeatedly shrouded North China in recent years, while natural dust from the west and northwest of China also frequently affects air quality in this region. Through continuous observation by a multi-wavelength Raman lidar, here we found that wintertime aerosols in North China are typically characterized by a pronounced vertical stratification, where scattering nonspherical particles (dust or mixtures of dust and anthropogenic aerosols) dominated above the planetary boundary layer (PBL), and absorbing spherical particles (anthropogenic aerosols) prevailed within the PBL. This stratification is governed by meteorological conditions that strong northwesterly winds usually prevailed in the lower free troposphere, and southerly winds dominated in the PBL, producing persistent and intense haze pollution. With the increased contribution of elevated dust to the upper aerosols, the proportion of aerosol and trace gas at the surface in the whole column increased. Model results show that, besides directly deteriorating air quality, the key role of the elevated dust is to depress the development of PBL and weaken the turbulent exchange, mostly by lower level cooling and upper level heating, and it is more obvious during the dissipation stage, thus inhibiting the dissipation of heavy surface anthropogenic aerosols. The interactions of natural dust and anthropogenic aerosols under the unique topography of North China increase the surface anthropogenic aerosols and precursor gases, which may be one of the reasons why haze pollution in North China is heavier than that in other heavily polluted areas in China.

scholarly journals The vertical aerosol type distribution above Israel – 2 years of lidar observations at the coastal city of Haifa

2021 ◽  
Author(s):  
Birgit Heese ◽  
Athena Augusta Floutsi ◽  
Holger Baars ◽  
Dietrich Althausen ◽  
Julian Hofer ◽  
...  
Keyword(s):  
Optimal Estimation ◽  
Relative Volume ◽  
Spherical Particles ◽  
Dust Particles ◽  
Source Attribution ◽  
Mass Source ◽  
Typing Method ◽  
Data Set ◽  
Multi Wavelength ◽  
Fine Mode

Abstract. For the first time, vertically resolved long-term lidar measurements of the aerosol distribution were taken in Haifa, Israel. The measurements were performed by a PollyXT multi-wavelength Raman and polarization lidar. The lidar was measuring continuously over a 2-year period from March 2017 to May 2019. The resulting data set is a series of manually evaluated lidar optical property profiles. To identify the aerosol types in the observed layers, a novel aerosol typing method developed at TROPOS is used. This method applies optimal estimation to a combination of the lidar-derived intensive aerosol properties to determine the statistically most-likely contribution per aerosol component in terms of relative volume. A case study that shows several elevated aerosol layers illustrates this method and shows e.g. that coarse dust particles are observed up to 5 km height over Israel. From the whole data set, the seasonal distribution of the observed aerosol components over Israel is derived. Throughout all seasons, and with the highest contributions in summer, autumn, and winter, coarse spherical particles like sea salt, due to the coastal site, but also hygroscopic grown continental aerosol that was transported over the Mediterranean Sea was observed. During spring, coarse non-spherical particles attributed to desert dust were the mostly observed particles. This is consistent with the distinct dust season in Spring in Israel. An automated time-height-resolved air mass source attribution method identifies the dust sources in the Saharan and the Arabian deserts. Fine mode spherical particles also contribute significantly to the observed aerosol mixture during the most seasons. These particles originate mainly from the industrial region at the bay of Haifa.

The Optical Constants of Coal, Char, and Limestone

1984 ◽  
Vol 106 (4) ◽  
pp. 678-683 ◽  
Author(s):  
M. Q. Brewster ◽  
T. Kunitomo
Keyword(s):  
Room Temperature ◽  
Optical Constants ◽  
Spherical Particles ◽  
Molecular Vibration ◽  
Molecular Absorption ◽  
Free Electrons ◽  
Absorption Bands ◽  
Specular Reflectance ◽  
Order Of Magnitude ◽  
Reflectance Measurements

The infrared optical constants, n and k, (n˜ = n − ik) of swelling and nonswelling coals, their respective char products, and limestone at room temperature have been obtained by a particle extinction technique using compressed KBr tablets. By assuming spherical particles and using Mie theory for the particle extinction measurements in conjunction with normal specular reflectance measurements from polished specimens, it is possible to obtain more accurate values for n and k than if the usual Fresnel reflectance technique is misapplied to samples that may appear specular but do not satisfy the stringent conditions necessary for invoking the Fresnel equations. Values of k for coal were found to be an order-of-magnitude smaller than previously reported values, with absorption due mainly to molecular vibration. The results for char evidenced that a significant increase in absorption by free electrons takes place upon devolatization and carbonization of coal. The limestone results demonstrated pronounced molecular absorption bands characteristic of CaCO3.

scholarly journals Elevated dust layers inhibit dissipation of heavy anthropogenic surface air pollution

2020 ◽  
Author(s):  
Zhuang Wang ◽  
Cheng Liu ◽  
Zhouqing Xie ◽  
Qihou Hu ◽  
Meinrat O. Andreae ◽  
...  
Keyword(s):  
Air Quality ◽  
North China ◽  
Spherical Particles ◽  
Trace Gas ◽  
Anthropogenic Aerosols ◽  
Haze Pollution ◽  
Multi Wavelength ◽  
Upper Level ◽  
Winter Time

Abstract. Persistent winter–time heavy haze incidents caused by anthropogenic aerosols have repeatedly shrouded North China in recent years, while natural dust from west and northwest of China also frequently affects air quality in this region. Through continuous observation by a multi–wavelength Raman lidar, here we found that aerosols in North China are typically characterized by a pronounced vertical stratification, where scattering non–spherical particles (dust or mixtures of dust and anthropogenic aerosols) dominated above the planetary boundary layer (PBL), and absorbing spherical particles (anthropogenic aerosols) prevailed within the PBL. This stratification is governed by meteorological conditions that strong northwesterly winds usually prevailed in the lower free troposphere, and southerly winds are dominated in the PBL, producing persistent and intense haze pollution. With the accumulation of elevated dust, the proportion of aerosol and trace gas at the surface in the whole column increased. Model results show that, besides directly deteriorating air quality, the key role of the elevated dust is to depress the development of PBL and weaken the turbulence exchange, mostly by lower–level cooling and upper–level heating, and it is more obvious during dissipation stage, thus inhibiting the dissipation of heavy surface anthropogenic aerosols. The interactions of natural dust and anthropogenic aerosols under the unique topography of North China increases the surface anthropogenic aerosols and precursor gases, which may be one of the reasons why haze pollution in North China is heavier than that in other heavily polluted areas in China.

scholarly journals Graphite and Interstellar Extinction

1965 ◽  
Vol 7 ◽  
pp. 5-10
Author(s):  
T. P. Stecher ◽  
Bertram Donn
Keyword(s):  
Cross Section ◽  
Optical Constants ◽  
Preceding Paper ◽  
Interstellar Extinction ◽  
Mie Scattering ◽  
Index Of Refraction ◽  
Spherical Particles ◽  
Complex Dielectric Constant ◽  
Integrated Cross Section ◽  
Complex Index Of Refraction

The Theory That Graphite Particles could be responsible for interstellar extinction is presented in references 1 and 2, and this paper will present evidence that further supports this contention. The complex dielectric constant (m = n(l — ik) for graphite has been measured as a function of energy by the authors of reference 3, and the optical constants as function of wavelength λ have been obtained from this measurement. A large variation occurs in both n and k at wavelengths below 3000 Å.The results reported in the preceding paper indicated the desirability of performing Mie scattering calculations on graphite. The measured values of the complex index of refraction corresponding to 17 wavelengths were used in the calculation for spherical particles. The IBM 7094 computer program for Mie scattering follows that of van de Hulst. (See ref. 4.) The Oort-van de Hulst size distribution (ref. 5), which may not be applicable to the type of particle discussed herein, has been used to obtain an integrated cross section for extinction.

scholarly journals Optical Properties of Cometary Dust

1991 ◽  
Vol 116 (2) ◽  
pp. 1003-1041 ◽  
Author(s):  
David J. Lien
Keyword(s):  
Electromagnetic Radiation ◽  
Optical Constants ◽  
Thermal Emission ◽  
Scattered Light ◽  
Mie Theory ◽  
Index Of Refraction ◽  
Spherical Particles ◽  
Spherical Approximation ◽  
Physical Parameters ◽  
Cometary Dust

AbstractCometary dust is observed in a variety of ways: scattered light, thermal emission, stellar occultations, coma and tail morphology, radar echoes, and meteors associated with comets. To interpret these observations with respect to the physical parameters of the dust (size, shape, and composition) and the properties of the dust-emitting region, the physics of how electromagnetic radiation interacts with small particles must be understood.The interaction between electromagnetic radiation and a small particle depends on the size, shape, and composition of the particle. The composition determines the optical constants of the material. Classically, a solid can be approximated by a collection of bound charges with a number of resonant frequencies. The optical constants (the index of refraction or dielectric constant) are a measure of the ability of the material to vibrate in response to an incoming electromagnetic wave. The laboratory measurement of optical constants is very difficult, and many published optical constants may be in error. Care must also be taken in choosing the optical constants that best represent the assumed composition of the cometary dust.Scattering theory is usually synonymous with Mie theory, although Mie theory pertains only to spherical particles. In many cases, homogeneous spheres may be good approximations of the dust in the coma, but an understanding of the effects of non-sphericity and heterogeneity is essential to determine the limitations of the spherical approximation. A variety of methods exist that, although computationally intensive, do provide insight into shape effects.

STEM Study of Surface Plasmon Excitation in Small Spherical Particles

1990 ◽  
Vol 48 (2) ◽  
pp. 42-43
Author(s):  
Daniel UGARTE
Keyword(s):  
Energy Loss ◽  
Spherical Particles ◽  
Small Particles ◽  
Bulk Materials ◽  
Low Loss ◽  
Plasmon Excitation ◽  
Surface Modes ◽  
Surface Plasmon Excitation ◽  
Analytical Electron ◽  
Analytical Electron Microscope

Small particles exhibit chemical and physical behaviors substantially different from bulk materials. This is due to the fact that boundary conditions can induce specific constraints on the observed properties. As an example, energy loss experiments carried out in an analytical electron microscope, constitute a powerful technique to investigate the excitation of collective surface modes (plasmons), which are modified in a limited size medium. In this work a STEM VG HB501 has been used to study the low energy loss spectrum (1-40 eV) of silicon spherical particles [1], and the spatial localization of the different modes has been analyzed through digitally acquired energy filtered images. This material and its oxides have been extensively studied and are very well characterized, because of their applications in microelectronics. These particles are thus ideal objects to test the validity of theories developed up to now.Typical EELS spectra in the low loss region are shown in fig. 2 and energy filtered images for the main spectral features in fig. 3.

Development of 200kV ultrahigh-resolution analytical electron microscope

1989 ◽  
Vol 47 ◽  
pp. 108-109
Author(s):  
T. Kaneyama ◽  
M. Naruse ◽  
Y. Ishida ◽  
M. Kersker
Keyword(s):  
Electron Microscope ◽  
Optical Constants ◽  
Materials Science ◽  
Objective Lens ◽  
The Finite Element Method ◽  
Ultrahigh Resolution ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Characteristic Features ◽  
Better Than

In the field of materials science, the importance of the ultrahigh resolution analytical electron microscope (UHRAEM) is increasing. A new UHRAEM which provides a resolution of better than 0.2 nm and allows analysis of a few nm areas has been developed. [Fig. 1 shows the external view] The followings are some characteristic features of the UHRAEM.Objective lens (OL)Two types of OL polepieces (URP for ±10' specimen tilt and ARP for ±30' tilt) have been developed. The optical constants shown in the table on the next page are figures calculated by the finite element method. However, Cs was experimentally confirmed by two methods (namely, Beam Tilt method and Krivanek method) as 0.45 ∼ 0.50 mm for URP and as 0.9 ∼ 1.0 mm for ARP, respectively. Fig. 2 shows an optical diffractogram obtained from a micrograph of amorphous carbon with URP under the Scherzer defocus condition. It demonstrates a resolution of 0.19 nm and a Cs smaller than 0.5 mm.

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