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 Ar(2)FeH(+) 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 C(2v) symmetry. The Ar-Fe-Ar bending mode at 46 cm(-1) is significantly populated at the temperature of the experiment, causing thermal broadening of the Fe-H stretch and its redshift with increasing internal energy.