This paper studies the vibrational nonlinear dynamics of nitrous oxide with Fermi coupling between the symmetric stretching and bending coordinates by classical dynamical potential approach. This is a global approach in the sense that the overall dynamics is evidenced by the classical nonlinear variables such as the fixed points and the focus are on a set of levels instead of individual ones. The dynamics of nitrous oxide is demonstrated to be not so much dependent on the excitation energy. Moreover, the localized bending mode is shown to be ubiquitous in all the energy range studied.
The highly excited vibrational levels of HCO in the electronic ground state, X^1A＇, are employed to determine the coefficients of an algebraic Hamiltonian, by which the dynamical potential is derived and shown to be very useful for interpreting the intramolecular vibrational relaxation （IVR） which operates via the HCO bending motion. The IVR inhibits the dissociation of H atom and enhances the stochastic degree of dynamical character. This approach is from a global viewpoint on a series of levels classified by the polyad number which is a constant of motion in a certain dynamical domain. In this way, the seemingly complicated level structure shows very regular picture, dynamically.
We have studied the temporal bond polarisabilities of para-nitroaniline from the Raman intensities by the algorithm proposed by Wu et al. in 1987 （Tian B, Wu G, Liu G 1987 J. Chem. Phys. 87 7300）. The bond polarisabilities provide much information concerning the electronic structure of the non-resonant Raman excited virtual state. At the initial moment by the 514.5 nm excitation, the tendency of the excited electrons （mapped out by the bond polarisabilities） is to spread to the molecular periphery, and the electronic structure of the Raman virtual state is close to the pseudoquinonoidic state. When the final stage of relaxation is approached, the bond polarisabilities of those peripheral bonds relax faster than those closer to the molecular core, the phenyl ring. The molecule is in the benzenoidic form as demonstrated by the bond polarisabilities after relaxation.
