Molecular Spectrocopy,1e

6.10 ELECTRONIC SPECTRUM OF POLYATOMIC MOLECULES

The theory of molecular spectroscopy learnt so far in the earlier Chapters has allowed us to describe the sizes, shapes and bond structures of diatomic molecules in the ground and excited states. Except few symmetrical molecules, the theoretical treatment of these molecules is quite complicated and cannot be described quantitatively. However, experimentally the absorption of radiation is a constitutive property and is often associated with the presence of specific groups in the molecules. These groups are characterised by absorption bands present in the selective regions of radiations and nearly independent of the rest of the molecule. In the infrared region, characteristic vibrational frequencies ...