char = I;code = 73
Identifying the molecular origin of global warming.char = W;code = 87
Publication: J Phys Chem A 2009 Nov 12 ;113(45)::12694-9. :doi: 10.1021/jp905097g.
We have investigated the physical characteristics of greenhouse gases (GHGs) to assess which properties are most important in determining the efficiency of a GHG. Chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), nitrogen fluorides, and various other known atmospheric trace molecules have been included in this study. Compounds containing the halogens F or Cl have in common very polar X-F or X-Cl bonds, particularly the X-F bonds. It is shown that as more F atoms bond to the same central atom the bond dipoles become larger as a result of the central atom becoming more positive. This leads to a linear increase in the total or integrated X-F bond dipole derivatives for the molecule, which leads to a nonlinear (quadratic) increase in infrared (IR) intensity. Moreover, virtually all of the X-F bond stretches occur in the atmospheric IR window as opposed to X-H stretches, which do not occur in the atmospheric window. It is concluded that molecules possessing several F atoms will always have a large radiative forcing parameter in the calculation of their global warming potential. Some of the implications for global warming and climate change are discussed.
PMID: 19694447
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