The Effect of Nonrigidity on the Line Strengths of Vibrational-Rotational Transitions

The effect of the difference in asymmetry of the ground and excited states of a vibrttional band on the line strengths of the vibrational-rotational transitions has been investigated. It is found that for sufficiently large Δk (∼0.1—0.2) in A- and C-type bands there is an enhancement of the line strengths of either the R or P branch, depending on whether or not k of the ground state is greater or less than k of the excited state. In B-type bands certain sub-bands are enhanced, but in general no branch of the band is enhanced as a whole.