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. Details here

• 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. Review here

• AP240: The expensive data acquisition card. Details here

• bitwise: The page of the ToF-AMS DAQ software that allows setting the baseline and threshold of the AP240. Details here

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

• C-ToF-AMS or C-AMS: Compact Time-of-Flight Aerosol Mass Spectrometer, first described in Drewnick et al. (AS&T, 2005).

• DAQ: ToF-AMS Data Acquisition Software. Details here

• HR-ToF-AMS or HR-AMS: High-Resolution Time-of-Flight Aerosol Mass Spectrometer, first described in DeCarlo et al. (Anal. Chem., 2006).

• Light Scattering: see LS-AMS below.

• LS-AMS: AMS with an internal adaptor used to measure particle size optically inside the AMS. First described by Cross et al. (AS&T, 2007)

• 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 a Jayne et al. (AS&T 2000) and Jimenez et al. (JGR 2003).

• 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. Details here.

• TOF-MS: Time of Flight mass spectrometer. Details here

• VUV-AMS: Vacuum Ultraviolet Ionization - AMS, first described by Northway et al. (AS&T 2007).

Analysis Software and Results

• APES: Analytical 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. Details here

• 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

• CE: Collection Efficiency. Definition here.

• Diff: The Difference Spectrum; difference in chopper-open mass spectrum and chopper-closed mass spectrum; typically considered the mass spectrum due to particles and gases entering the AMS. See also 'semi-refractory'.

• Elemental Analysis or EA: the technique to determine the elemental composition of a mixed organic aerosol based on HR-TOF-AMS signals. This is currently implemented in the APES software. Introduced by Aiken et al. (Anal. Chem., 2007) and (ES&T, 2008).

• 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'

• Igor or Igor Pro: a commercial data analysis software package developed by Wavemetrics, Inc., in Oregon, US. All the standard AMS data analysis software is written in Igor. Details on here.

• 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 (R) species: chemical components of aerosol that are not volatile enough to vaporize in the AMS in a time scale of less than a day or so, and thus are never observed by the instrument. Examples include black carbon and most chemical forms or mineral dust (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. Some details here.

• 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). See HR-ToF-AMS above.

• ipf: Igor Procedure File. Details on Igor here.

• 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). Details here

• 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. Details here.

• 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+)

• Wavemetrics: the company that makes Igor Pro. Details here

PMF-Related

• BBOA: Biomass Burning Organic Aerosol

• bootstrapping: a statistical method used with PMF to estimate uncertainty of PMF solutions by solving a many resampled versions of the original dataset (see bootstrapping at Wikipedia)

• FPEAK: a "knob" in PMF that can be used to explore the some rotations of the solution space. (more on the PMF-AMS wiki)

• 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 factors do not directly represent POA directly, but the POA concentration can be estimated with some assumptions it.

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

• PMF: Positive Matrix Factorization. A least-squares, bilinear factorization that is constrained to give only positive values in the factor matrices. (more on the PMF-AMS wiki)

• 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 (i.e. Q = sum over matrix (residual/error)^2)

• seeds: the seed value used to generate random values used at the start of a PMF run. It's possible that different different solutions may result from different seeds. (more on the PMF-AMS wiki)

• SV-OOA: Semi-Volatile Oxidized Organic Aerosol