Cavity Enhanced Spectroscopy Methods for Measurement of Optical Properties of Aerosol Particles PDF Download

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Publisher:
ISBN:
Category :
Languages : en
Pages : 284

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Author: Abdur Rasheed
Publisher:
ISBN:
Category :
Languages : en
Pages : 136

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Author: Ruth Signorell
Publisher: CRC Press
ISBN: 142008562X
Category : Nature
Languages : en
Pages : 513

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Helping you better understand the processes, instruments, and methods of aerosol spectroscopy, Fundamentals and Applications in Aerosol Spectroscopy provides an overview of the state of the art in this rapidly developing field. It covers fundamental aspects of aerosol spectroscopy, applications to atmospherically and astronomically relevant problem

Author: Alison Bain
Publisher:
ISBN:
Category :
Languages : en
Pages :

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"Aerosol is ubiquitous in our atmosphere, yet still poses great uncertainty to climate models. Central to accurate predictions of aerosol radiative forcing is an accurate description of the scattering and absorption of solar radiation by aerosol, which can be described by the complex refractive index (RI). The RI of aerosol depends on the wavelength of incident light and the temperature as well as its chemical composition. In the atmosphere, aerosol may contain a number of different organic and inorganic components. Furthermore, as aerosol is transported though the atmosphere and encounters air of varying relative humidity its water content will change to remain at equilibrium with its surroundings. All of these factors must be taken into consideration in order to accurately determine the RI of atmospheric aerosol.The RI of single, optically trapped particles can be determined through the collection and fitting of Mie scattered light. By monitoring optically trapped particles it is possible to mimic atmospheric conditions. Importantly for investigating the RI of aerosol, single particle experiments allow for the characterization of supersaturated states not accessible through bulk measurements. Throughout this thesis, the refractive indices of various aerosol types are determined using optical trapping methods.First, in order to find the most accurate method of determining the RI of aerosol, retrieval using the morphology-dependent resonances (MDRs) in the Mie scattering spectrum is compared to phase function fitting. Using the MDRs is found to be more accurate and less computationally demanding than phase function fitting. MDRs and the Mie scattering spectrum are then used throughout the rest of this thesis to determine the optical properties of aerosol.Next, the optical properties of absorbing particles are investigated. Single, absorbing particles are held in a photophoretic trap, illuminated with a broadband light source and the broadband Mie scattering spectrum is collected. Here, the full Mie scattering spectrum is fit using Lorentzian oscillators to describe the absorption features observed as scattering minima in the spectra. Using the causal relationship between the real and imaginary parts of the RI described by the Kramers-Kronig relation, the wavelength-dependent complex RI is determined for these particles.The complex RI of weakly absorbing particles is then considered. Using cavity-enhanced Raman spectroscopy, while slowly heating the particle by increasing the trapping beam power, both the real and imaginary parts of the RI of several aqueous solutions whose optical properties are relevant to aqueous sea-salt particles and aqueous organic aerosol are measured. The far-UV transitions that give rise to the RI in the visible region for weak absorbers is modeled with an effective Lorentzian oscillator. The effective oscillator model accurately describes both the real and imaginary parts of the RI of aqueous solutions across a wide range of water activities and optical wavelengths. It is shown that mixing rule calculations utilizing oscillator parameters from solutions containing a single solute and water can be used to predict the optical properties of aqueous solutions containing multiple solutes.Finally, this model is extended to consider the contributions of individual ions to theRI of aerosol. Since the absorption of weakly absorbing aerosol is small and is often neglected, broadband scattering is utilized to determine only the real part of the refractiveindex. The oscillator parameters determined for ions accurately predict the RI as a function of both water content and wavelength for aqueous salts and strong acids.Furthermore, the RI of ternary organic-inorganic mixtures using these oscillatorparameters agree with experimentally determined refractive indices. In addition, the effectof temperature on RI within the framework of the effective oscillator modelis also explored"--

Author: Giel Berden
Publisher: John Wiley & Sons
ISBN: 9781444308242
Category : Science
Languages : en
Pages : 344

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Cavity Ring-Down Spectroscopy: Techniques and Applications provides a practical overview of this valuable analytical tool, explaining the fundamental concepts and experimental methods, and illustrating important applications. Designed as both an introductory text and a reference source, this book is relevant for scientists unfamiliar with CRDS who are interested in using the technique in their research, as well as experienced users.

Author: Kerry J. Knox
Publisher: Springer Science & Business Media
ISBN: 3642163483
Category : Science
Languages : en
Pages : 209

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Book Description
Aerosols play a critical role in a broad range of scientific disciplines, such as atmospheric chemistry and physics, combustion science, drug delivery and human health. This thesis explores the fundamentals of a new technique for capturing single or multiple particles using light, and for characterising these particles by Raman or fluorescence spectroscopy. The outcome of this research represents a significant development in optical manipulation techniques, specifically in optical tweezing. These findings can be applied to studies of the mass accommodation of gas-phase water molecules adsorbing onto a water surface. Not only is this a fundamental process of interest to physical chemists, but it is important for understanding the role of aerosol particles in the atmosphere, including their ability to become cloud droplets. This new strategy for investigating aerosol dynamics is fundamental in helping us understand the indirect effect of aerosols on the climate.

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Category : Atmospheric aerosols
Languages : en
Pages : 113

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Scientists have been observing a change in the climate since the beginning of the 20th century that cannot be attributed to any of the natural influences of the past. Natural and anthropogenic substances and processes perturb the Earth's energy budget, contributing to climate change. In particular, aerosols (particles suspended in air) have long been recognized to be important in processes throughout the atmosphere that affect climate. They directly influence the radiative balance of the Earth's atmosphere, affect cloud formation and properties, and are also key air pollutants that contribute to a variety of respiratory and cardiovascular diseases. Despite their importance, aerosol particles are less well-characterized than greenhouse gases with respect to their sources, temporal and spatial concentration distribution, and physical and chemical properties. This uncertainty is mainly caused by the variable and insufficiently understood sources, formation and transformation processes, and complex composition of atmospheric particles. Instruments that can precisely and accurately measure and characterize the aerosol physical and chemical properties are in great demand. Atmospheric relative humidity (RH) has a crucial impact on the particles' optical properties; the RH dependence of the particle extinction coefficient is an important parameter for radiative forcing and thus climate change modeling. In this work a Humidity-Controlled Cavity Ring-Down (HC-CRD) aerosol optical instrument is described and its ability to measure RH dependent extinction coefficients and related hygroscopicity parameters is characterized.

Author: Weidong Chen
Publisher: Elsevier
ISBN: 0128156899
Category : Science
Languages : en
Pages : 634

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Book Description
Advances in Spectroscopic Monitoring of the Atmosphere provides a comprehensive overview of cutting-edge technologies and monitoring applications. Concepts are illustrated by numerous examples with information on spectroscopic techniques and applications widely distributed throughout the text. This information is important for researchers to gain an overview of recent developments in the field and make informed selections among the most suitable techniques. This volume also provides information that will allow researchers to explore implementing and developing new diagnostic tools or new approaches for trace gas and aerosol sensing themselves. Advances in Spectroscopic Monitoring of the Atmosphere covers advanced and newly emerging spectroscopic techniques for optical metrology of gases and particles in the atmosphere. This book will be a valuable reference for atmospheric scientists, including those whose focus is applying the methods to atmospheric studies, and those who develop instrumentation. It will also serve as a useful introduction to researchers entering the field and provide relevant examples to researchers and students developing and applying optical sensors for a variety of other scientific, technical, and industrial uses. Overview of new applications including remote sensing by UAV, laser heterodyne radiometry, dual comb spectroscopy, and more Features in-situ observations and measurements for real-world data Includes content on leading edge optical sensors

Author: Manfred Wendisch
Publisher: John Wiley & Sons
ISBN: 3527653236
Category : Science
Languages : en
Pages : 659

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Book Description
This first comprehensive review of airborne measurement principles covers all atmospheric components and surface parameters. It describes the common techniques to characterize aerosol particles and cloud/precipitation elements, while also explaining radiation quantities and pertinent hyperspectral and active remote sensing measurement techniques along the way. As a result, the major principles of operation are introduced and exemplified using specific instruments, treating both classic and emerging measurement techniques. The two editors head an international community of eminent scientists, all of them accepted and experienced specialists in their field, who help readers to understand specific problems related to airborne research, such as immanent uncertainties and limitations. They also provide guidance on the suitability of instruments to measure certain parameters and to select the correct type of device. While primarily intended for climate, geophysical and atmospheric researchers, its relevance to solar system objects makes this work equally appealing to astronomers studying atmospheres of solar system bodies with telescopes and space probes.

Author:
Publisher: Walter de Gruyter GmbH & Co KG
ISBN: 1501519379
Category : Science
Languages : en
Pages : 215

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Atmospheric aerosols are an important and a highly complex component of the Earth’s atmosphere that alter the radiative forcing and the chemical composition of the gas phase. These effects have impacts on local air quality and the global climate. Atmospheric Aerosol Chemistry outlines research findings to date in aerosol chemistry and advances in analytical tools used in laboratory studies for studying their surface and bulk reactivity.