The dynamics of a passive particle in a hydrodynamical flow behind a cylinder is investigated. The velocity field has been determined both by a numerical simulation of the Navier-Stokes flow and by an analytically defined model flow. To analyze the Lagrangian dynamics, we apply methods coming from chaotic scattering: periodic orbits, time delay function, decay statistics. The asymptotic delay time statistics are dominated by the influence of the boundary conditions on the wall and exhibit algebraic decay. The short time behavior is exponential and represents hyperbolic effects.
Recently Quack and co-workers have developed a spectroscopic Hamiltonian that uncovers for Bromochlorofluoromethane vibrational excitation in the electronic ground state, the anharmonicities and resonant interactions between the normal modes that determine and fit the measured spectrum. In this paper using this spectroscopic Hamiltonian (no PES) and simple quantum, semiclassical and nonlinear classical methods of analysis a great deal of further information is extracted. Namely in polyad 5 and 8 the energy levels are disentangled into three and four different types of simple motion respectively. Each type of motion gives rise to simple level series. Each series is the quantization of a simple to visualize intramolecular motion. Quantum numbers which are close to conserved quantities are assigned to every state. The most extraordinary of these motions is a rapid cone like rotation of the HC bond atop the asymmetrical triangular pyramid of the heavy part of the molecule. The spectrum of these states shows an approximate double degeneracy even though the molecule is of C1 symmetry; the rapid circulation of the hydrogen atom causes the dynamics to become insensitive to the differences between the various halogen masses and positions.
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