DESCRIPTION OF NON-RIGID MOLECULAR STRUCTURE THROUGH DYNAMICAL SYMMETRY BREAKING
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Publisher:Ohio State University
A novel algebraic scheme has been developed for investigating the structure and dynamics of explicitly non-rigid molecules, as manifest most simply in the spectral features of quasi-linear triatomic species. Our approach permits such ``floppy'' systems to be envisioned as undergoing a ``shape-changing phase transition'' between two dynamical symmetry limits of an encompassing algebraic framework (e.g., the Lie algebra $U(3)$ for triatomic bending modes) with intermediate configurations of the nuclei corresponding to situations that break dynamical symmetries. A simple model Hamiltonian has been shown to embody appropriate effects (i.e., negative or alternating positive/negative vibrational anharmonicity) for describing transformations between the ``rigidly-bent'' and ``rigidly-linear'' limiting geometries that characterize quasi-linear triatomic molecules. This theoretical treatment has been exploited successfully to interprete vibrational energy level patterns reported for the ``soft'' bending degree of freedom in the ground electronic states of magnesium hydroxide $(MgOH)$ and its deuterated isotopomer $(MgOD)$. Finally, a coherent (or intrinsic) state formalism has been shown to afford a near-direct connection between algebraic analyses and the potential energy surfaces mediating various regimes of non-rigidity, thereby furnishing valuable insight into the physical processes that govern ``floppy'' behavior.
Author Institution: Yale University; Center for Theoretical Physics, Yale University; Center for Theoretical Physics, Yale University