FAQ AMS Glossary

This is a glossary of terms and acronyms typically used by the AMS community. It is a work in progress - so is by no means complete or comprehensive. Please continue to add and edit!

Hardware and Data Acquisition

• ACSM: Aerosol Chemical Speciation Monitor, also known as "Mini-AMS". A smaller and cheaper version of the AMS using a small quadrupole, designed for monitoring purposes.

• AMS: Aerosol Mass Spectrometer. In our community it always means the Aerodyne AMS, but a few other groups have named other instruments "AMS", which are unrelated to the Aerodyne AMS.

• CRiTTR: Piece of software to run the pulsers and move the chopper independently of the AMS Data Acquisition software (DAQ)

• DAQ: Data Acquisition Software

• Light Scattering:

• MAB-AMS: Metastable Atom Bombardment AMS. An adaptation of the AMS which uses soft ionization for analysis of the OA with lower fragmentation.

• Mini-AMS: see ACSM above.

• Q-AMS: Quadrupole AMS. The original version of the AMS, described in Jayne et al. (AS&T 2000).

• SP-AMS: Soot Particle AMS. New instrument developed which combines the SP2 (Single Particle Soot Photometer) particle vaporization and the AMS ionization and mass spectrometry.

• TOF-MS: Time of Flight mass spectrometer

Analysis Software and Results

• APES: Analytic Procedure for Elemental Separation. An Igor tool for performing an elemental analysis (i.e. O/C ratio). In Pika 1.07 most of this code was merged with the pika code, but a version of APES remain as a stand-alone Igor code.

• Background: In general this term should be avoided as it is too ambiguous. (Background ambient measurement conditions? Background instrumental signal? etc.) The use of 'Closed mass spectra' is encouraged where appropriate.

• Baseline: In a mass spectra, the 'region between the peaks' for an open, closed or difference mass spectra.

• Closed: The mass spectrum taken with the chopper in the 'blocked' position, and typically considered instrument background and gas-phase contribution to AMS signal

• Diff: The Difference Spectrum; difference in chopper-open mass spectrum and chopper-closed mass spectrum; typically considered the mass spectrum due to particle signal

• f_x: the fraction of the total organic signal that is observed at m/z = x. E.g. f₄₄ is the fraction of the total OA signal at m/z 44. Sometimes also written as 44/Org or 44/OA.

• fragments: a vaporized molecule is ionized in the AMS to a series of ions, which are then detected by either a quadrupole or time-of-flight mass spectrometer; the resulting ions are referred to as 'fragments'

• Non-refractory (NR) species: chemical components of aerosol that are volatilized in the AMS, and are observed in the "Difference spectrum". This requires evaporation in a time scale shorter than chopper open/closed movement, whish is typically 3-5 seconds. Examples include the usual AMS species: sulfate, nitrate, ammonium, chloride, and organic (OA). Note that these species can also have some semi-refractory signal, although this is typically a small fraction (5-10% of the NR signal under typical operating conditions).

• Refractory species: chemical components of aerosol that are not volatile enough to vaporize in the AMS in a time scale of at least a few hours, and thus are never observed by the instrument. Examples include black carbon (see SP2-AMS).

• Semi-refractory(SR) species: chemical components of aerosol that are relatively less volatile, and only slowly vaporize in the AMS. Functionally, they are observed in both the the Closed and Open signals (time-scale for vaporization is much longer than the time scale of open/closed chopper movement). Examples include some chemical forms of Pb (lead) and possibly NaCl.

• HR: High Resolution (as opposed to UMR, typically referring to either the High Resolution Time of Flight Aerosol Mass Spectrometer, or to the data derived from that instrument)

• ipf: Igor Procedure File

• Open: Mass spectra acquired when the chopper is in the 'open' position - both air and aerosols are entering and being detected

• PIKA: Peak Integration by Peak Analysis. This is a somewhat contorted acronym, but this name really indicates "High Resolution Analysis" or HR analysis where individual peaks (C3H6 and C2H2O at ~ m/z 42).

• SPARROW: Single PARicle Retrieval Of Waves. The Igor analysis tool for AMS light scattering data.

• SQUIRREL: SeQUential Igor data RetRiEvaL. The Igor analysis tool for non-Quad AMS data.

• UMR: Unit Mass Resolution (as opposed to HR: ie, signal observed at m/z 28 is UMR, whereas HR data typically shows two peaks, one from N2+ and another from CO+)

PMF-Related

• BBOA: Biomass Burning Organic Aerosol

• HOA: Hydrocarbon-like Organic Aerosol

• LV-OOA: Low volatility-oxygenated organic aerosol

• OA: organic aerosol. Often also referred to as OM, organic mass. Some authors also refer to this as POM, for particulate organic mass.

• OOA: Oxygenated Organic Aerosol

• OOA-1: the more oxidized fraction of OOA. Frequently referred to as LV-OOA.

• OOA-2: the less oxidized fraction of OOA. Frequently referred to as SV-OOA.

• POA: Primary Organic Aerosol, that emitted into the atmosphere in the particle phase. PMF cannot determine POA directly, but with some assumptions it can be used to estimate the POA concentration.

• PET: PMF Evaluation Tool. An interface for examining the results of many PMF analyses.

• PMF: Positive Matrix Factorization

• Q or Q value: Q is the objective function that PMF minimizes to find its solution. It is the sum of the squared residual at each datapoint, divided by the squared error estimate for that datapoint.

• SV-OOA: Semi-Volatile Oxidized Organic Aerosol