Dynamically motivated spectroscopy of small polyatomic molecules

Abstract

Molecular vibrational dynamics far from equilibrium, or in the vicinity of saddle points, are of utmost importance in chemistry. However, most of the standard models used by chemists only perform well near local minima in the potential energy surface. Several spectroscopic techniques are developed and applied to the study of molecules in excited states, including chirped-pulse millimeter wave spectroscopy and adaptations of millimeter-wave optical double resonance. Models for Franck-Condon factors in the linear-to-bent S₁-S₀ transition of acetylene elucidate the dynamics of bright states observed in the fluorescence spectrum and provide insight for the design of spectroscopic schemes for accessing barrier-proximal vibrational levels. IR-UV double resonance spectroscopy enables characterization of the source of staggering in the antisymmetric stretch progression of the C̃ state of SO₂, which arises due to vibronic interactions that lead to non-equivalent equilibrium SO bond lengths.