| definition |
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Particle Analysis by Laser Mass Spectrometry (PALMS) is a laser
ionization mass spectrometer which makes in-situ measurements of
the chemical composition of individual aerosol
particles. Aerosols are brought into a vacuum system and
individual particles are detected by light scattered as they
cross the beam of a continuous laser. The scattered light signal
gives a rough indication of the size of the particle and
provides a trigger for an excimer laser (193nm), which is pulsed
so its beam hits the particle to ionize molecules and
atoms. These ions are analyzed with a time of flight mass
spectrometer to provide a complete mass spectrum from each
particle. The instrument is capable of measuring particles from
0.2 to 3 microns in diameter. Analysis is complete less then 1
millisecond after the aerosols enter the inlet. The instrument
can acquire either positive or negative ion spectra.
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