Premium
Absorption cross sections for water vapor from 183 to 193 nm
Author(s) -
Cantrell Christopher A.,
Zimmer Audrey,
Tyndall Geoffrey S.
Publication year - 1997
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/97gl02100
Subject(s) - water vapor , monochromator , analytical chemistry (journal) , materials science , absorption (acoustics) , absorption cross section , absorption spectroscopy , vapor pressure , optics , wavelength , chemistry , cross section (physics) , optoelectronics , environmental chemistry , physics , organic chemistry , quantum mechanics , composite material
Absorption cross sections for water vapor at 184.9 nm were measured using a standard low‐pressure mercury lamp light source, optically filtered to isolate the spectral region near the emission line. The light from the source was detected using a solar‐blind phototube. Experiments were performed over a wide range of water column amounts, using neat water vapor and water vapor/nitrogen mixtures, with four methods to determine the water vapor concentration in the cell. Absorption cross sections were measured between 0 and 80°C. The results from these experiments yield a cross section of 7.14 (± 0.2) × 10 −20 cm² molecule −1 at 25°C with a small positive temperature dependence (about 4% between 0 and 80°C). This result is about 30% greater than current recommendations. The absorption spectrum was also measured at discrete wavelengths between 183 and 193 nm using a scanning double monochromator system. The cross section of deuterated water vapor was determined at 184.9 nm. The implications of the changes in the H 2 O cross section for the calibration of atmospheric OH and HO 2 measurements using the 184.9 nm photolysis of water vapor are discussed.