The v3 infrared spectrum of the He-NH 4 complex

Abstract

The mid-infrared spectrum of the ionic complex He-NH+4 has been recorded in the vicinity of the triply degenerate v3 (t2) vibration of the free ammonium ion. Apart from a small blue shift (≈ 0.7 cm-1), the spectrum of the complex closely resembles that of the monomer. Ab initio calculations predict a vertex-bound minimum structure with an intermolecular well depth De ≈ 150 cm-1, a center-of-mass separation of Re ≈ 3.17 Å and barriers for internal rotation less than 30 cm-1.