München 2004 – wissenschaftliches Programm
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UP: Umweltphysik
UP 3: Atmosph
äre und Klima II
UP 3.1: Fachvortrag
Montag, 22. März 2004, 16:30–16:45, HS 118
Atmospheric Detection of Water Dimers via Near-Infrared Absorption — •Andreas Lotter1, Christina Peters1, Hartmut Bösch1,2, and Klaus Pfeilsticker1 — 1Institut für Umweltphysik, Universität Heidelberg, Im Neuenheimer Feld 229, 69120 Heidelberg — 2Jet Propulsion Laboratory, Mail-Stop 183-601, 4800 Oak Grove Drive, Pasadena, CA 91109 USA
Weakly bonded pairs of water molecules (H2O)2 , or water dimers (WD), may play an important role in atmospheric physics, atmospheric photochemistry and climate, but the overlap of most of its spectral features with the water monomer (WM) has made detection difficult.
We report on WD absorption measurements by means of atmospheric long path (18.34 km) Differential Optical Absorption Spectroscopy (DOAS) of the near infrared OH stretching mode |0⟩f|4⟩b overtone transition predicted to be located near 746 nm. Our observation is in reasonable agreement with the known thermo chemistry, calculated and measured structure, and spectroscopy (band strength, shape, and width) of the WD.
The observation implies that the WD |0⟩f|4⟩b band is located at 749.5 nm, with a full width at half maximum of Γ ≈ 19.4 cm−1, and that its band strength ranges between 1.23 × 10−22 and 5.25 × 10−22 cm/molecule. WDs absorb approximately 0.42 − 1.5 W/m2 of solar radiation globally averaged.