Atmospheric Composition & Chemical Processes: Instruments

Strat-CIMS (High altitude Chemical Ionization mass spectrometer)

Strat-CIMS instrument team — Patrick Veres, Martin Breitenlechner, Gordon Novak, Drew Rollins, and Samantha Lee with the Strat-CIMS instrument during SABRE 2022. Photo: Chelsea Thompson, NOAA / CIRES

Principle of the Measurement

The NOAA Strat-CIMS is a chemical ionization mass spectrometer specifically designed for in situ measurements of gas phase inorganic and organic analytes in the upper troposphere and lower stratosphere. The instrument uses a custom-built ionization source that employs a commercially available photoionization krypton lamp, to produce iodide ions (I^-) which react with target analytes through an adduct formation reaction. Adduct ions are subsequentially detected with a commercial high-resolution time-of-flight mass spectrometer from TOFWERK / Aerodyne Research Inc.

This NOAA Strat-CIMS instrument was engineered specifically for deployment in harsh environments including low ambient pressures (60 mbar) and temperatures (190K). Operation on remote airborne platforms is fully automated.

Species Measured

Reactive Nitrogen species: N₂O₅, HNO₃
Halogen species: BrO, Br₂, Cl₂, ClNO₂
Organic species: HCOOH (formic acid) and other low to intermediate volatility organics

Time Response

Instrumental response <1 sec, Field response is limited by inlet surface affinity for each compound

Detection Limit

Precision on 1s data various by species

Accuracy

(30% + 0.03 pptv) for N₂O₅
(30% + 4 pptv) for ClNO₂
(20% + 2 pptv) for Cl₂
(20% + 4 pptv) for Br₂
(15% + 160 pptv) for HCOOH

Manufacturer

Tofwerk / Aerodyne Research Inc., custom modified for airborne deployment with support from design lead Rich McLaughlin

Field Projects

Stratospheric Aerosol processes, Budget and Radiative Effects (SABRE) 2022, NASA WB-57

Key Publications

Breitenlechner, M., G.A. Novak, J.A. Neuman, A.W. Rollins, and P.R. Veres, A versatile vacuum ultraviolet ion source for reduced pressure bipolar chemical ionization mass spectrometry, Atmospheric Measurement Techniques, doi:10.5194/amt-15-1159-2022, 2022.