Jahn--Teller effect in the photoelectron spectrum of iron pentacarbonyl

Journal Article · Tue Sep 15 04:00:00 EDT 1981 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.442407· OSTI ID:6249809

Hubbard, J L; Lichtenberger, D L

High quality photoelectron spectra of gaseous Fe(CO)/sub 5/ excited by HeI, HeII, and ArI photons have been obtained. Major attention is focused on the primarily metal 3d ionizations, which occur in the binding energy region from 7 to 11 eV. Ionization to the /sup 2/E' positive ion state (centered at 8.6 eV) clearly shows the effects of Jahn--Teller distortions in the positive ion. This ionization results in two ionization bands of approximately equal intensity and shape separated by 0.38 eV at room temperature. These bands broaden and the splitting increases to 0.47 eV at 473 /sup 0/K. Ionization to the /sup 2/E'' positive ion state, centered at 9.9 eV, is much less influenced by the Jahn--Tellar effect. There is no discernable splitting of this band at room temperature. These observations are discussed in terms of the electronic structure and bonding of Fe(CO)/sub 5/. Simple model calculations of the energies of the doubly degenerate electronic states in relation to the appropriate doubly degenerate normal vibrational modes are used to investigate the splitting. The magnitudes of the /sup 2/E' and /sup 2/E'' splittings are reproduced very well, and the temperature dependence is reproduced within experimental error. It is found that the vibrational motion primarily responsible for the splitting is a low frequency OC--Fe--CO bending in the equatorial plane. This bending is found in two normal modes, one of which is closely related to the Berry pseudorotation process. The splitting of the /sup 2/E' ionization is clear experimental evidence in the gas phase that the preferred geometry of d/sup 7/ M(CO)/sub 5/ is not D/sub 3h/ in this case.

• Research Organization: Department of Chemistry, University of Arizona, Tucson, Arizona 85721
• OSTI ID: 6249809
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 75:6; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

640302* -- Atomic
Molecular & Chemical Physics-- Atomic & Molecular Properties & Theory
74 ATOMIC AND MOLECULAR PHYSICS
CARBONYLS
ELECTRON SPECTROSCOPY
IONIZATION
IRON COMPOUNDS
JAHN-TELLER EFFECT
PHOTOELECTRON SPECTROSCOPY
PHOTOIONIZATION
SPECTROSCOPY
TRANSITION ELEMENT COMPOUNDS