Hyperfine-resolved rovibrational and rotational spectroscopy of OH+ (X 3Σ-)

Abstract

The OH+ (X3Σ-) radical cation has been investigated by combining a 4 K 22-pole ion trap apparatus with high-resolution IR and THz radiation sources. Applying different types of action spectroscopic methods, the fundamental vibrational band in the 3 µm range and the spin manifold of the N = 1 ← 0 rotational transition around 1 THz have been extended and refined, whereas the spin manifold of the N = 2 ← 1 rotational transition scattered around 2 THz has been measured for the first time. Although all rotational hyperfine lines are affected by considerable Zeeman splittings, a simulation of their contours allowed us to extract the field-free center frequencies with high accuracy. A global fit including literature values and the 16 hyperfine lines studied in this work was performed, improving the ground state spectroscopic parameters of OH+ considerably.