Resonance enhanced multiphoton ionization spectroscopy of NHD2via the 1E′′-state

Abstract

Rotational analysis of the (2 + 1) resonance enhanced multiphoton ionization (REMPI) spectrum of the ¹E′′ Rydberg state of the ammonia isotopologue NHD₂ is reported. While the electronic degeneracy is lifted in NHD₂ the splitting is small enough that interactions between the two states must be considered, particularly to model the intensity of the transitions. A simple model is developed to account for these interactions, relating them to terms present in the symmetric isotopologues. Spectroscopic parameters for the zero point and (ν₂′ = 1–6) vibrational levels of the B ¹E′′ state have been derived using this model and the spectra are accurately simulated for the first time using the PGOPHER program. The current work provides the basis for on-going velocity map imaging studies of rotational energy transfer in the mixed isotopologues of ammonia.