Is ammonium iodide an ion pair H3N+ H⋯I– or a hydrogen-bonded species H3N⋯HI in the gas phase?
Abstract
The ground-state rotational spectrum of the heterodimer (NH3,HI) has been observed by pulsed-nozzle, Fourier-transform microwave spectroscopy. A quartz oreservoir/nozzle attached to the outlet of a solenoid valve allowed pulses of ammonium iodide vapour/argon to be produced without encountering metal surfaces. The observed spectroscopic constants are consistent with a hydrogen-bond description H3N⋯HI rather than an ion-pair H3N–⋯I– description of the observed species.