Nitrogen, , makes up about of the atmosphere by volume, far more than carbon…
PHYSICS · Multi-part · Fermi University Physics · Atomic, Molecular & Optical Physics · Molecular structure and spectra · Molecular structure and spectra
Deriving the Spectrum, Ch Polyatomic molecules: normal modes and symmetry
Problem
Nitrogen, N2, makes up about 78% of the atmosphere by volume, far more than carbon dioxide's 0.04%, yet it contributes essentially nothing to the greenhouse effect. Its single vibration has ωe≈2359cm−1.
((a)) Using the result for homonuclear diatomic dipole functions and the electric-dipole transition rule, explain why N2 has no allowed infrared vibrational transition at any order of the anharmonic expansion, not merely a weak one.
((b)) State whether N2's vibration is active in the Raman spectrum instead, and why.
((c)) Explain why nitrogen's very high atmospheric abundance is irrelevant to this conclusion.