This long - range force among atoms or molecules arises from the temporary appearance of electric dipole moments in the particles. (sciencedaily.com)
Overtones for H2O and CO2 are allowed for electric dipole transitions because of small anharmonicities in the vibrational potential energy but are as it says, really weak. (realclimate.org)
N2 and O2 vibrational transitions period are forbidden by symmetry for electric dipole transitions. (realclimate.org)