Abstract

Iron is the most abundant transition metal in the interstellar medium (ISM), and is thought to be involved in a variety of astrochemical processes. Here, we present the infrared multiple photon dissociation (IRMPD) spectra of Ar 1,2FeH + and their deuterated isotopologues in the region of 2240-14 000 cm -1. The Fe-H overtone stretching mode in ArFeH + and Ar 2FeH + is observed at 3636 ± 28 cm -1 and 3659 ± 13 cm -1, respectively. Deuteration shifts these bands to 2618 ± 31 cm -1 and 2650 ± 14 cm -1 in ArFeD + and Ar 2FeD +, respectively. Additionally, the spectra of Ar 2FeH + and Ar 2FeD + feature broad transitions at ∼2200-4000 cm -1 and ∼4500-6500 cm -1. We assign these bands to electronic transitions from the thermally populated X 5A 2/X' 5A 1 ground state manifold into the A' 5B 2 and B 5A 1 states, which we model with multi-reference quantum chemical calculations including spin-orbit coupling. The calculations show that these transitions are symmetry forbidden in FeH + and in the equilibrium geometry of ArFeH +/ArFeD +, while the zero-point oscillation of the bending mode of the triatomic molecule leads to some oscillator strength. Upon addition of the second argon atom, the transitions become weakly allowed in the equilibrium geometry of Ar 2FeH +/Ar 2FeD + due to symmetry reduction from C ∞v to C 2v.

MeSH

Multiple Chronic Conditions, Chemistry, Physical

Cited by

• Infrared Multiple Photon Dissociation Spectroscopy of the H-H Stretching Mode and Low-Lying Electronic Transitions in Fe(H) and Fe(D). J Phys Chem A, 2025