1.19 PRINe orntion in the infrared region occurs due to excitation of molecule from the lower to the higher l level. Since each vibrational level 1s aSsociated With a number of closely spaced rotational levels, IR spectra may be regarded as vibrational rotational spectra. at the atams in a molecule are not ridiigy helld but keen on rihratina to and fro ahamt a
Each of the normal modes of vibration of heteronuclear diatomic molecules in the gas phase also contains closely-spaced (1-10 cm difference) energy states attributable to rotationa...