Knowledge Bank

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 $\nu 2+\nu 3+\nu \ast 2$ at about $6050cm-1$. and $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\nu \ast$ both near $10100cm-1$. 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 $\nu 3\ast$ 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.