We have measured 62 lines in the v4 band of the ammonium ion (NH+4) using infrared diode laser velocity modulation spectroscopy of a hydrogen/ammonia discharge. The transitions were fitted to a fourth order spherical rotor hamiltonian yielding v4 = 1447.2158(50) cm-1, B4 = 5-85121(24)cm-1 and 2B4ζ4 = 5-3757(11)cm-1. As in methane, the v4 band is strongly perturbed by the higher frequency v2 band. A comparison of the measured molecular properties with ab initio calculations is given.
ASJC Scopus subject areas
- Molecular Biology
- Condensed Matter Physics
- Physical and Theoretical Chemistry