Band strengths for C-H stretching polyads of CHBr3 calculated by use of a two-dimensional electric dipole moment surface from density functional theory

Band strengths of the Fermi resonance polyads involving C-H stretching and bending vibrations for the CHBr3 molecule are calculated with a one-dimensi onal dipole function and a two-dimensional dipole surface. These are obtain ed by the ab initio density functional method. Both treatments reproduce th e interpolyad band strengths quite well, while the two-dimensional dipole m oment surface is superior to the one-dimensional one in modeling the intrap olyad band strength pattern, indicating the importance of the bending vibra tions in dipole moment surface and intensities calculations. The different behavior of interpolyad band strengths of CHBr3 compared to CHCl3, with an intensity anomaly occurring in the latter case, is illustrated by "dipole-w eighted" overlap integrals. (C) 2001 American Institute of Physics.