Assigning vibrational spectra of chaotic molecules

A method is presented for detailed level-by-level approximate quantum number assignment and spectral pattern organization for a molecular Hamiltonian with a mixture of regular and chaotic classical dynamics. The large-scale bifurcation structure is determined for a spectroscopic Hamiltonian for H2O. A Husimi transform method is used to assign approximate quatum numbers to the levels, and the spectrum is grouped into regular patterns. Pronounced spectral reorganization is observed in the region of most highly chaotic dynamics.