The Zeeman effect of the interstitial Fe defect was investigated by using high-resolution Fourier-transform spectroscopy. Two sets of experimentally observed line spectra had previously been identified as optical excitations of the neutral interstitial, Fei0. The first set arose when an electron was excited into a shallow donor-like state, Fei0 + hv → Fe+ + e-, where the electron was decoupled from the Fe+ core whose ground state was a 4Tl term. The second set arose when an excited electron of al symmetry was coupled, by exchange interaction, to the Fe+ core; thus yielding a 5Tl final state. The Zeeman behavior of these transitions was studied in order to verify the attribution of the states and of the effective-mass like character of the decoupled electron. Experiments yielded multiplet splitting of the 4Tl and 5Tl states, due to spin-orbit interaction, but large deviations from the Landé interval rule were observed as well as a marked increase in intensity of the high-energy components. Analysis confirmed that the 4Tl and 5Tl states were closely related, and a dynamic Jahn-Teller distortion was suggested to be the predominant mechanism which was responsible for the non-Landé behavior.

Neutral interstitial iron center in silicon studied using Zeeman spectroscopy A.Thilderkvist, G.Grossmann, M.Kleverman, H.G.Grimmeiss: Physical Review B, 1998, 58[12], 7723-33