DYNAMICAL TUNNELING AND MOLECULAR-SPECTRA

We show on very general grounds that for a sufficiently high density o f states (typically greater than or equal to 100 per cm(-1)) but low e nough energy (so that chaos does not play a role) most quantum eigenst ates of moderate sized valence-bonded molecules are likely to be deloc alized by tunneling interactions between would-be localized states. On e implication of this is that energy is essentially never trapped in l ocalized modes or bonds in polyatomic molecules above a threshold ener gy. Another implication is that spectroscopically prepared zero-order states, which typically possess some local quality, will bear the impr int of the tunneling and spawn narrow spectral clusters whose width is characteristic of the tunneling.