1. Temperature dependences of mechanisms responsible for the water-vapor continuum absorption. II. Dimers and collision-induced absorption
- Author
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Q. Ma, R. H. Tipping, Claude Leforestier, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), Department of Physics and Astronomy [Tuscaloosa), University of Alabama [Tuscaloosa] (UA), Department of Applied Physics, and Columbia University [New York]
- Subjects
010504 meteorology & atmospheric sciences ,Continuum mechanics ,Infrared ,Dimer ,General Physics and Astronomy ,Infrared spectroscopy ,01 natural sciences ,Omega ,chemistry.chemical_compound ,chemistry ,Infrared window ,0103 physical sciences ,[PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph] ,Physical and Theoretical Chemistry ,Atomic physics ,010306 general physics ,Microwave ,Water vapor ,0105 earth and related environmental sciences - Abstract
International audience; We investigated the magnitude and temperature dependence (T dependence) of the dimer absorption in the region of 0–600 cm−1 and the collision-induced absorption (CIA) in the region of 0–1150 cm−1. Together with our previous study of the self water-vapor continuum contributions resulting from far-wing line shapes of the allowed H2O lines in the infrared window between 800 and 1150 cm−1, we find that the three mechanisms have completely different T dependence behaviors. The dimer absorption has the strongest negative T dependence and the continuum absorption from far wings of the allowed lines has a moderately strong negative one. Meanwhile, the CIA exhibits a mild T dependence. In addition, their T dependence patterns are quite different. The T dependence of the far-wing theory varies significantly as the frequency of interest ω varies. For CIA, in general, its T dependence is mildly negative, but becomes slightly positive in the window region between the H2O bands. In contrast, the T dependence of the dimer absorption varies slightly as ω varies. In the microwave and submillimeter region, its T dependence becomes uniform. Concerning the relative importance for each of these three mechanisms, we find that in the infrared widow, the far-wing contributions are the dominant source of the self-continuum. Within the band, its contributions are definitely responsible for the measured continuum data. But, it is impossible to draw quantitatively conclusions on its relative importance unless one is able to improve the accuracy of the local line calculations significantly. On the other hand, within the pure rotational band, the dimer absorptions are a minor contributor to the self-continuum measurements, and its role becomes more important in the microwave and submillimeter regions. Finally, based on our study we conclude that contributions to the self-continuum from CIA in the frequency region of 0–1150 cm−1 are negligible.
- Published
- 2010