Knowledge Bank

Infrared far infrared (IR-FIR) double resonance experiments on ($NH3$)$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ in a jet are performed. Based on the results the nature of the tunneling splitting detected in former IR and FIR studies can be identified. It appears that the ($NH3$)$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ complex exhibits the following feasible motions: internal rotation of each monomer, interchange tunneling, and inversion tunneling. The rigid structure is classified in C, where a plane of symmetry is assumed. The FIR transitions reported so far and three new bands reported in this work are assigned within the group $G144$. It is found that the inversion splitting for some of the bands is almost quenched upon excitation of the $v2$ umbrella motion the inversion splitting amounts to $3.7cm-1$.