A laser-induced fluorescence instrument for detecting tropospheric OH and HO2: Characteristics and calibration

Ian C. Faloona, David Tan, Robert L. Lesher, Nathan L. Hazen, Christopher L. Frame, James B. Simpas, Hartwig Harder, Monica Martinez, Piero Di Carlo, Xinrong Ren, William H. Brune

Research output: Contribution to journalArticlepeer-review

141 Scopus citations


Measurement capability for the detection of atmospheric OH and HO2 has been developed at the Pennsylvania State University over the last decade. The instrument is used in two forms: an aircraft configuration, Airborne Tropospheric Hydrogen Oxides Sensor (ATHOS), and the configuration used on towers, Ground-based Tropospheric Hydrogen Oxides Sensor (GTHOS). The instrument uses ultraviolet laser induced fluorescence (LIF) to detect OH in air that is pulled by a vacuum pump through a small inlet into a low-pressure detection chamber; HO2 is detected by reacting it with NO to form OH, which is detected by LIF in a second detection chamber. In the calibration, equal amounts of OH and HO2 ranging from 0.15 pptv to 100 pptv are produced via photolysis of water vapor by the 185 nm emission from a low-pressure Hg lamp. Estimated absolute uncertainty at the 2σ confidence level is ±32% for both OH and HO2. The dependence of the instrument detection sensitivity has been quantified for changes in ambient water vapor, pressure, laser power, and the flow velocity of ambient air past the inlet. During the last 7 years, the instrument has been deployed in multi-investigator intensive field studies 5 times on the NASA DC-8 aircraft and 8 times on ground-based towers. The descriptions in this manuscript detail our cumulative wisdom of the instrumental response and calibration techniques developed over this time.

Original languageEnglish (US)
Pages (from-to)139-167
Number of pages29
JournalJournal of Atmospheric Chemistry
Issue number2
StatePublished - Feb 2004

All Science Journal Classification (ASJC) codes

  • Environmental Chemistry
  • Atmospheric Science


Dive into the research topics of 'A laser-induced fluorescence instrument for detecting tropospheric OH and HO2: Characteristics and calibration'. Together they form a unique fingerprint.

Cite this