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New Study Details How CO2 Molecules Absorb and Scatter Light Energy

23 April 2008

AIP Bulletin of Physics News. A new joint study by French and Russian scientists shows in detail how carbon dioxide molecules absorb and sometimes scatter light energy not only singly but also during inter-molecular collisions.

Michael Chrysos and his colleagues at the University of Angers (France) and the University of Saint Petersburg (Russia) have derived the first exact mathematical formulas that can be used to calculate how collisions between molecules modify the absorption spectra for those molecules. The formulas allow researchers to look at how greenhouse warming comes about.

...the new study improves the study of greenhouse warming in several ways: (1) It allows us to calculate exactly how much of the IR photon energy (intercepted by a CO₂ molecule during a CO₂-CO₂ collision) is transferred directly to the neighboring gas molecule, where it is converted to kinetic energy of translation; it’s about half of the IR photon energy. The other half of the IR photon energy goes to rotation of the two molecules, which will then start spinning more quickly. (2) It shows how to introduce higher-order effects, such as the simultaneous collision of three molecules. On Venus such collisions should add significantly to IR absorption. (3) It provides evidence that inter-molecular interactions at close range separations (interactions acting when the colliding molecules approach to within a few angstroms) have no effect on absorption, a conclusion in conflict with the mainstream belief that short range interactions should play a substantial role in collision induced molecular absorption.

Resources

• Chrysos et al. (2008) Exact Low-Order Classical Moments in Collision-Induced Bands by Linear Rotors: CO₂-CO₂ Phys. Rev. Lett. 100, 133007 (2008) DOI: 10.1103/PhysRevLett.100.133007

April 23, 2008 in Brief | Permalink | Comments (1) | TrackBack (0)

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Comments

OK. But on item 2) Venus's atmosphere is 97% CO2 and average surface temp 467C. Earth's atmosphere contains 0.0378 CO2 thereby lowering the incidence of CO2-CO2 collision induced absorption and scattering.

Posted by: gr | Apr 23, 2008 11:38:47 AM

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