Nonlinearity of the Dipole Moment Surface and Intensities Anomaly of CHCl₃

Relative absorption intensities of the Fermi resonance polyads of isolated C-H chromophore for the CHCl₃ molecule are calculated by one-dimensional dipole moment surface which had been obtained by the ab initio density functional method B3PW91 with 6-311++G(3df, 2pd) basis set, and agree very well with the experimental results. It is shown that the nonlinearity of the dipole moment surface in the vicinity of the equilibrium configuration is responsible for the intensities anomaly, i.e. the unusual strong intensities of the second Fermi resonance polyad.