Progress on $NH_{2}$: More rotational assignments, a Hamlitonian for band origins, and modeling of N-H stretch intramolecular dynamics

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Ohio State University

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Our continuing application of microwave-detected microwave optical double resonance to rotational assignment of NH2: vibrational overtones and combination bands from $6000cm^{-1}$ to $18000cm^{-1}$ has lead to the assignment of several new bands, These include $\nu_{2}+ \nu_{3} + \nu^{2}_{*}$ at about $6050cm^{-1}$. and $^{3}\nu_{*}$ both near $10100 cm^{-1}$. The hamiltonian being used to fit band origins in the N-H stretch overtone regions includes Darling-Dennison or local mode coupling which mixes $\nu_{2}$ and $\nu_{3}^{*}$ and the Fermi resonance between $2\nu_{4}$, and the N-H stretches in an essentially phenomenological way but also uses x-k relations to reduce the number of independent parameters. With the assumption that all overtone intensity derives from the local mode state, this hamiltonian leads directly to a time-dependent picture of delocalization of the initial local-mode state that would be created by a sub picosecond light pulse. The five quanta region is shown to be local mode in character, but lower regions rapidly delocalize into normal mode components.


Author Institution: Harvard Chemistry Department, 12 Oxford Street; Princeton Chemistry Department, Washington Road, Princeton, New Jersey 08544