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Instrument: RSMS : Rapid Single-particle Mass Spectrometer
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Description
During a month in the summer of 1999, individual aerosol
particles were sized and analyzed using a Rapid Single-particle
Mass Spectrometer (RSMS) in Atlanta. RSMS aerodynamically
focuses one particle size at a time to the source region of a
mass spectrometer and employs a 193 nm excimer laser to desorb
and ionize the particle components.The ions are analyzed in a
single time-of-flight mass spectrometer and the spectrum is
digitally recorded. Spectra are only saved if the ion peak in
the spectrum is above a threshold level. Background spectra
were determined and flagged. Particle size scans were initiated
periodically and each size was sampled until 30 particle hits
were obtained, unless the sampling time became
excessive. Aerodynamic particle sizes ranged from about 40 to
1300 nm and were partitioned into nine discrete size classes
logarithmically spaced, roughly, over the range. Single
particle data are valuable because for instance a) they are
collected and analyzed real ti me so have excellent temporal
resolution, b) the particle-to-particle composition variations
(external mixing properties) can be assessed, and c) key
particle sources are easily identified since the particles
retain source characteristics. The data resulting from these
measurements consist of an aerodynamic particle size and a
positive mass spectrum of the components for each particle,
along with the date and time of measurement and other
incidental measurement parameters such as the laser pulse
energy. Support for RSMS measurements has been provided by the
EPA Supersite program and additional funding from the EPA and
NSF.

[Summary provided by NASA]