Photoelectron spectroscopy of FeO and FeO2 : Observation of low-spin excited states of FeO and determination of the electron affinity of FeO2

The photoelectron spectra of FeO and FeO2 2 are obtained at 3.49 eV photon energy. Transitions to the ground state ~D! and three low-lying excited states ~S, S, and D! of FeO are observed. The two low-spin excited states found at 6770 and 8310 cm above the ground state, respectively, have not been observed before. The two S states, characteristic of detachment of a nonbonding electron from the FeO anion, exhibit no vibrational progressions while a vibrational progression is observed for each of the two D states. The two high-spin states D and S are in agreement with a previous photoelectron study @P.C. Engelking and W. C. Lineberger, J. Chem. Phys. 66, 5054 ~1977!#. The D state has a vibrational frequency of 800 ~50! cm. The spectrum of FeO2 2 only shows one major feature with little vibrational structure at this photon energy. The electron affinity of FeO2 is determined to be 2.358 ~0.030! eV. © 1995 American Institute of Physics.