Atmospheric methane measurement instrument using a Zeeman-split He--Ne laser

Journal Article · Fri Dec 01 04:00:00 EST 1989 · Applied Optics; (USA)

DOI:https://doi.org/10.1364/AO.28.005016· OSTI ID:7070147

McManus, J B; Kebabian, P L; Kolb, C E ^[1]

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1. Aerodyne Research, Inc., 45 Manning Road, Billerica, Massachusetts 01821-3976 (US)

We report the construction of an atmospheric methane measurement instrument based on a Zeeman-split IR He--Ne laser. The laser has a transverse magnetic field over P{approximately}2/3 of its gain length and can oscillate at an (unsplit) frequency (2947.91 cm{sup {minus}1}) centered on a methane absorption line, or on either of two frequencies split by {plus minus}0.055 cm{sup {minus}1} from the center, with low CH{sub 4} absorption. The laser is tuned to dwell sequentially at each frequency, giving two differential absorption measurements in each 46-ms tuning cycle. Atmospheric measurements are made using two multiple pass absorption cells, one with fast (0.75-s) and one with slow (5-s) flow response times. Fluctuations in ambient CH{sub 4} of {approximately}20-ppb (rms, 1-s averaging) are detected, with interference fringe effects the dominant noise source. The instrument has operated in a field experiment (NASA GTE/ABLE-3A) in Alaska.

• OSTI ID: 7070147
• Journal Information: Applied Optics; (USA), Journal Name: Applied Optics; (USA) Vol. 28:23; ISSN 0003-6935; ISSN APOPA
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540120* -- Environment
Atmospheric-- Chemicals Monitoring & Transport-- (1990-)
AIR POLLUTION MONITORING
ALASKA
ALKANES
ATMOSPHERIC CHEMISTRY
CHEMISTRY
EARTH ATMOSPHERE
FEDERAL REGION X
HYDROCARBONS
INFRARED SPECTRA
METHANE
NORTH AMERICA
ORGANIC COMPOUNDS
SPECTRA
TROPOSPHERE
USA