A5023485550- Atmospheric chemistry and aerosols
- Atmospheric aerosols and clouds
- Atmospheric Ozone and Climate
- Spectroscopy and Laser Applications
- Vehicle emissions and performance
- Advanced Chemical Physics Studies
- Air Quality and Health Impacts
- Advanced Aircraft Design and Technologies
- Catalytic Processes in Materials Science
- Laser Design and Applications
- Air Quality Monitoring and Forecasting
- Gas Sensing Nanomaterials and Sensors
- Electron and X-Ray Spectroscopy Techniques
- Atomic and Molecular Physics
- Plasma Diagnostics and Applications
- Diamond and Carbon-based Materials Research
- Semiconductor materials and devices
- Advanced Combustion Engine Technologies
- Catalysis and Oxidation Reactions
- Mass Spectrometry Techniques and Applications
- Metal and Thin Film Mechanics
- Gas Dynamics and Kinetic Theory
- Analytical Chemistry and Sensors
- Chemical Thermodynamics and Molecular Structure
- Atmospheric and Environmental Gas Dynamics
Aerodyne Research
2015-2024
University Hospital of Wales
2006
California Institute of Technology
2003
Brookhaven National Laboratory
2003
United States Department of Energy
1978-1998
Office of Science
1998
Lawrence Berkeley National Laboratory
1975-1996
University of California, Berkeley
1975-1996
Iowa State University
1975-1980
Ames National Laboratory
1975-1980
An inter-comparison study of instruments designed to measure the microphysical and optical properties soot particles was completed. The following mass-based were tested: Couette Centrifugal Particle Mass Analyzer (CPMA), Time-of-Flight Aerosol Spectrometer—Scanning Mobility Sizer (AMS-SMPS), Single Soot Photometer (SP2), Particle-Aerosol Spectrometer (SP-AMS) Photoelectric Sensor (PAS2000CE). Optical measured absorption (photoacoustic, interferometric, filter-based), scattering (in situ),...
We present initial results obtained from an optical absorption sensor for the monitoring of ambient atmospheric nitrogen dioxide concentrations (0-200 ppb). This utilizes cavity attenuated phase shift spectroscopy, a technology related to ringdown spectroscopy. A modulated broadband incoherent light source (a 430-nm LED) is coupled optically resonant formed by two high-reflectivity mirrors. The presence NO(2) in cell causes signal received photodetector that proportional concentration....
We describe a robust, compact, field deployable instrument (the CAPS PMssa) that simultaneously measures airborne particle light extinction and scattering coefficients thus the single albedo (SSA) on same sample volume. With an appropriate change in mirrors source, measurements have been made at wavelengths ranging from 450 to 780 nm. The measurement is based cavity attenuated phase shift (CAPS) techniques as employed PMex monitor; measured using integrating nephelometry by incorporating...
We present results obtained from a greatly improved version of previously reported nitrogen dioxide monitor (Anal. Chem. 2005, 77, 724−728) that utilizes cavity attenuated phase shift spectroscopy (CAPS). The sensor, which detects the optical absorption within 20 nm bandpass centered at 440 nm, comprises blue light emitting diode, an enclosed stainless steel measurement cell (26 cm length) incorporating resonant near-confocal design and vacuum photodiode detector. An analog heterodyne...
Molecular beams of a number aryl and aryl–alkyl halide molecules were photodissociated using an excimer laser at 193 nm fragment translational energy distributions measured. Previous work had shown that dissociation takes place by spin–orbit dependent crossing from intermediate (π, π*) delocalized state to triplet (σ, σ*) localized on the C–X bond (X=Cl,Br,I). The vibrational remains in aromatic framework; thus distribution reflects only electronic but not state. This fact is exploited...
We present laboratory and field measurements of aerosol light extinction ( σep ) using an instrument that employs Cavity Attenuated Phase Shift (CAPS) spectroscopy. The CAPS monitor comprises a emitting diode (LED), optical cavity acts as the sample cell, vacuum photodiode for detection. particle is determined from changes in phase shift distorted waveform square-wave modulated LED transmitted through cell. 3-σ detection limit under dry particle-free air 3 Mm–1 1s integration time....
Gaseous CS2 was dissociated at 193 nm into CS and S. The translational internal energy distributions of the fragments were measured. There is now overwhelming evidence that upper electronic state S3 predissociative. In fact there are three states importance, initially excited S3, a which dissociates to CS(X 1Σ) S(1D) triplet S(3P). rotationally with an average rotational ∼3.5 kcal/mole. vibrational populations also strongly inverted for both 1D 3P dissociations their surprisal plots linear....
Abstract. Sustainable aviation fuels (SAFs) have different compositions compared to conventional petroleum jet fuels, particularly in terms of fuel sulfur and hydrocarbon content. These differences may change the amount physicochemical properties volatile non-volatile particulate matter (nvPM) emitted by aircraft engines. In this study, we evaluate whether comparable nvPM measurement techniques respond similarly produced three blends SAFs fuels. Multiple SAF (Jet A-1) were combusted a...
We present details of an apparatus capable measuring optical extinction (i.e., scattering and/or absorption) with high precision and sensitivity. The employs one variant cavity enhanced detection, specifically attenuated phase shift spectroscopy, using a near-confocal arrangement two reflectivity (R∼0.9999) mirrors in tandem enclosed cell 26cm length, light emitting diode (LED), vacuum photodiode detector. square wave modulated from the LED passes through absorption is detected as distorted...
Abstract. An evaluation of the Cavity Attenuated Phase Shift particle light extinction monitor (CAPS PMex) using a combination 3-wavelength Integrating Nephelometer (NEPH) and filter-based Particle Soot Absorption Photometer (PSAP) was carried out both laboratory-generated test particles ambient aerosols. accurate determination fixed pathlength correction for CAPS PMex made by comparing measurements monodisperse PSL spheres in with Mie scattering calculations to account presence...
Presented here is an overview of non-volatile particulate matter (nvPM) emissions, i.e. "soot" as assessed by TEM analyses samples collected after the exhaust a J-85 turbojet fueled with Jet-A well blends and Camelina biofuel. A unifying explanation provided to illustrate combustion dynamics biofuel fuel. The variation primary particle size, aggregate size nanostructure are analyzed function blend across range engine thrust levels. postulate based on where fuels start along soot formation...
X-ray photoelectron spectroscopy (XPS) and an ultrahigh vacuum compatible microwave discharge effusive beam source have been used to study the reactions of atomic molecular fluorine on Si(111) surfaces. Fluorine uptake changes in binding energy peak shape for Si 2p F 1s XPS peaks measured as functions exposure. The results indicate that is dissociatively chemisorbed form SiF2-like surface species. This reaction saturates at approximately one monolayer coverage. In contrast, extends well...
Abstract Aerosol optical properties were measured in Beijing summer and winter using a state‐of‐the‐art cavity attenuated phase shift single scattering albedo monitor (CAPS PM ssa ) along with aerosol composition measurements by mass spectrometers aethalometers. The SSA directly the CAPS showed overall agreements those derived from colocated measurements. However, substantial differences observed during periods low values both winter, suggesting that interpretation of needs to be cautious....
Abstract. Optical properties of flame-generated black carbon (BC) containing soot particles were quantified at multiple wavelengths for produced using two different flames: a methane diffusion flame and an ethylene premixed flame. Measurements made (i) nascent particles, (ii) thermally denuded (iii) that coated then denuded, leading to the collapse initially lacy, fractal-like morphology. The measured mass absorption coefficients (MACs) depended on maturity generation but similar between...
Diamond (100) substrates have been fluorinated under ultrahigh vacuum conditions with both atomic and molecular fluorine. X-ray photoelectron spectra of the resulting samples indicate that fluorine, F, reacts efficiently at 300 K producing a saturation coverage about three quarters monolayer (one ≂1.6×1015 cm−2) after 40 monolayers exposure. The carbon fluoride adlayer is thermally stable to 700 but slowly desorbs temperatures above this. In contrast, F2, quite slowly; less than one fifth...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThermodynamic and kinetic properties of the metaphosphate anion, PO3-, in gas phaseMichael Henchman, A. Viggiano, John F. Paulson, Freedman, J. WormhoudtCite this: Am. Chem. Soc. 1985, 107, 5, 1453–1455Publication Date (Print):March 1, 1985Publication History Published online1 May 2002Published inissue 1 March 1985https://pubs.acs.org/doi/10.1021/ja00291a081https://doi.org/10.1021/ja00291a081research-articleACS PublicationsRequest reuse...
Diamond (100) and (111) surfaces have been exposed to beams of atomic molecular fluorine chlorine in an ultrahigh-vacuum environment. X-ray photoelectron spectroscopy, low-energy electron diffraction, thermal desorption techniques used elucidate the chemistry involved. F atoms add both diamond (100)-(1×1) (111)-(2×1) form a carbon-monofluoride species which reaches saturation level approximately three-quarters monolayer at 300 K. In other aspects their behavior, differ. On surface, rate atom...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTFast-flow studies of methylidyne radical kinetics at 290 KS. M. Anderson, A. Freedman, and C. E. KolbCite this: J. Phys. Chem. 1987, 91, 24, 6272–6277Publication Date (Print):November 1, 1987Publication History Published online1 May 2002Published inissue 1 November 1987https://pubs.acs.org/doi/10.1021/j100308a039https://doi.org/10.1021/j100308a039research-articleACS PublicationsRequest reuse permissionsArticle Views133Altmetric-Citations46LEARN...
We describe an apparatus for the measurement of vapor pressures solids or liquids at ambient temperatures (260 K < T 350 K) demonstrated to operate over a pressure range 10−2–10−6 Torr (1–10−4 Pa), but capable being extended lower by least order magnitude. It employs Knudsen cell produce effusive molecular beam, only small fraction which is deposited on cooled (225 quartz crystal microbalance (QCM). Vapor values are derived from mass gain rate determined QCM, temperature, and fixed geometric...
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