Abstract:Q-space analysis is applied to the light scattering phase function of a wide variety of non-spherical and irregularly shaped particles including a great many types of dusts, fractal aggregates, spheroids, irregular spheres, Gaussian random spheres, thickened clusters and nine types of ice crystals. The phase functions were either experimental data or calculations. This analysis method uncovers many specific and quantitative similarities and differences between the scattering by various shapes and also when com… Show more
“…Plotting the curve in this way reveals power-law trends, which are often useful 26 , 27 , 29 to infer particle characteristics from such scattering patterns. Here, one can see the ( qR Mie ) −3 power law for example 49 . Figure 2 Spherical aerosol particle.…”
Coarse mode atmospheric aerosol particles are abundant in agricultural, desert, and urban environments. Accurate characterisation of these particles’ morphology is an important need in scientific and applied contexts, especially to advance our understanding for how such aerosols influence solar radiative forcing of the atmosphere. Elastic light scattering is a standard method to study aerosol particles in a contact-free manner, wherein measured scattering patterns are interpreted to infer particle morphology. Due in part to the absence of wave-phase information in these measurements, the inference is not unique, a difficulty generally known as the inverse problem. An alternative approach is digital holography where wave-phase information is encoded in the measurements. We show that digital holography and spatial filtering can solve the inverse problem for free-flowing aerosol particles in the sense that a measured scattering pattern can be uniquely associated with the particle size, shape, and orientation producing it.
“…Plotting the curve in this way reveals power-law trends, which are often useful 26 , 27 , 29 to infer particle characteristics from such scattering patterns. Here, one can see the ( qR Mie ) −3 power law for example 49 . Figure 2 Spherical aerosol particle.…”
Coarse mode atmospheric aerosol particles are abundant in agricultural, desert, and urban environments. Accurate characterisation of these particles’ morphology is an important need in scientific and applied contexts, especially to advance our understanding for how such aerosols influence solar radiative forcing of the atmosphere. Elastic light scattering is a standard method to study aerosol particles in a contact-free manner, wherein measured scattering patterns are interpreted to infer particle morphology. Due in part to the absence of wave-phase information in these measurements, the inference is not unique, a difficulty generally known as the inverse problem. An alternative approach is digital holography where wave-phase information is encoded in the measurements. We show that digital holography and spatial filtering can solve the inverse problem for free-flowing aerosol particles in the sense that a measured scattering pattern can be uniquely associated with the particle size, shape, and orientation producing it.
“…Otherwise, MAC represents the mass 47 absorption coefficient; in some studies, the mass absorption efficiency (MAE) is also used [12-48 15]. In comparison to solution-phase spectroscopy, the mass-specific absorption cross-section 49 and the mass absorption coefficient approximate the linear and non-linear regimes in absorption 50 as a function of absorber number density (e.g. dilute and high concentration limits), respectively.…”
Section: Introduction 25mentioning
confidence: 99%
“…morphology) on MAC for a collection of monomers is 285 also significant. However, calculating MAC with elaborate particle geometries is a computational 286 challenge best addressed using complex optical routines such as the discrete dipoles 287 approximation and the superposition T-matrix method as described in studies by Mishchenko 288 and Mackowski, among others [45][46][47][48][49]. The AAE of the all data shown in Figure 6 was calculated using Eq.…”
Mass absorption coefficient spectra were measured between λ = 500 nm and 840 nm for nine forms of highly-absorbing carbonaceous aerosol: five samples generated from gas-, liquid-and solid-fueled flames; spark-discharge fullerene soot; graphene and reduced graphene oxide (rGO) crumpled nanosheets; and fullerene (C 60 ) assemblies. Aerosol absorption spectra were measured for size-and mass-selected particles and found to be dependent on fuel type and formative conditions. Flame-generated particles had morphologies consistent with freshly emitted black carbon (BC) with mass absorption coefficients (MAC) ranging between 3.8 m 2 g -1 and 8.6 m 2 g -1 at λ = 550 nm. Absorption Ångström exponents (AAE) -i.e. MAC spectral dependence -ranged between 1.0 and 1.3 for flame-generated particles and up to 7.5 for C 60 . The dependence of MAC and AAE on mobility diameter and particle morphology was also investigated. Lastly, the current data were compared to all previously published MAC measurements of highly-absorbing carbonaceous aerosol. Mass absorption coefficient spectra were measured between λ = 500 nm and 840 nm for nine 13 forms of highly-absorbing carbonaceous aerosol: five samples generated from gas-, liquid-and 14 solid-fueled flames; spark-discharge fullerene soot; graphene and reduced graphene oxide (rGO) 15 crumpled nanosheets; and fullerene (C 60 ) assemblies. Aerosol absorption spectra were measured 16 for size-and mass-selected particles and found to be dependent on fuel type and formative 17 conditions. Flame-generated particles had morphologies consistent with freshly emitted black 18 carbon (BC) with mass absorption coefficients (MAC) ranging between 3.8 m 2 g -1 and 8.6 m 2 g -1
19at λ = 550 nm. Absorption Ångström exponents (AAE) -i.e. MAC spectral dependence -ranged 20 between 1.0 and 1.3 for flame-generated particles and up to 7.5 for C 60 . The dependence of MAC 21 and AAE on mobility diameter and particle morphology was also investigated. Lastly, the current 22 M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 2 data were compared to all previously published MAC measurements of highly-absorbing 23 carbonaceous aerosol. 24
“…Sorensen et al [21] provide a detailed review of the power of Q-space analysis that offers general insights on the optical properties of particles and allows the discovery of patterns useful for the interpretation of these properties. After a general introduction of the basic concepts using Mie and Rayleigh scattering theories, the authors expand the analysis to the more complex topic of the optical properties of irregular particles.…”
Section: Theoretical and Numerical Studiesmentioning
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
