Toward Detection of FeH+in the Interstellar Medium: Infrared Multiple Photon Dissociation Spectroscopy of Ar2FeH+

Abstract

The iron hydride molecular cation FeH+is expected to be present in the interstellar medium. Because of the lack of laboratory data, it is yet to be identified in spectrally resolved astronomic observations. As a benchmark for computational predictions and to guide an experimental search for the ro-vibrational lines of FeH+, we performed infrared multiple photon dissociation (IRMPD) spectroscopy of FeH+tagged with two argon atoms. The Fe-H stretching mode in Ar2FeH+is observed at 1860 cm-1. Combination bands of the Fe-H stretch with the two Fe-H bending and the asymmetric Fe-Ar stretching modes are observed at 2012 cm-1, 2054 cm-1, and 2078 cm-1. Quantum chemical calculations show that the molecule has C2vsymmetry. The Ar-Fe-Ar bending mode at 46 cm-1is significantly populated at the temperature of the experiment, causing thermal broadening of the Fe-H stretch and its redshift with increasing internal energy.