Spectroscopy and intramolecular dynamics of highly excited vibrational states of NH3

Abstract

Using the recently developed technique of microwave-detected, microwaveoptical double resonance, we have for the first time been able to assign the rotational structure in the local-mode progression of NH₃. This work has resulted in a near doubling of the number of rotationally assigned bands of this well studied molecule. We have reproduced our observed spectrum with an effective vibrational Hamiltonian that includes both Darling–Dennison and Fermi resonance coupling between ν₁, ν₃ and 2ν₄. Because these interactions were not included previously, we have also determined the first relible anharmonic constants for this molecule. We have used this effective Hamiltonian to determine the intramolecular dynamics of NH₃ for ca. 1 ps.