Direct Evidence from Gas-Phase Atomic Spectra for an Unscreened Intra-Atomic Origin of Outer-Core Multiplet Splittings in Solid Manganese Compounds

Abstract

We compare for the first time gas-phase 3s and 3p spectra from atomic Mn with corresponding spectra from the solid compounds MnF2 and MnO. These spectra are found to be strikingly similar, indicating that the solid-state spectra have a dominant origin in unscreened intra-atomic multiplet splittings, perhaps with correlation-induced satellites. Such outer-core hole states are thus not describable in terms of a simple superposition of fully screened and poorly screened spectra as recently proposed.PACS numbers: 79.60.Eq., 32.80.FbIn this Letter, we compare core-level photoelectron spectra of a free transition-metal atom with corresponding spectra from solid compounds for the first time in an attempt to resolve more precisely the exact nature of the multiplet splittings and final-state extra-atomic screening processes involved. We first discuss prior theoretical models for such effects and then consider our experimental data in this context.Multiplet splittings in transition-metal core-level binding energies have been known for some time. 1 " 5 For outer-core levels such as 3s and 3p in the 3d series, these effects in ionic and partially ionic materials were first interpreted in terms of a strongly intra-atomic L-S term splitting in the final state of the system with the core hole present. For the simplest case of 3s emission from a metal atom or ion with a ground-state spin of S, this splitting is due to the exchange interaction between the unpaired outermost 3d electrons and the remaining 3s electron. This model predicts a doublet with a separation which is proportional to [25 + 1] x [3s-3d exchange integral], a direct consequence of the Van Vleck theorem. 1,4,5 For intrashell interactions such as 3s-3d, 3p-3d, and 4y-4/, it was quickly realized that the splittings predicted by this model were too large by about a factor of 2, and that correlation effects beyond a simple Hartree-Fock-level approach could be responsible for this reduction in the observed separation between the two peaks. 1 " 3 Bagus, Freeman, and Sasaki 2 then showed that a more correct final-state wave function for an isolated Mn 2+ ion that included correlation in the final states via configuration interaction (CI) not only predicted well the reduction of the splitting of the dominant doublet in the 3s region for ionic compounds containing Mn 2+ , but also gave rise to additional lower-intensity satellite peaks at higher binding energies. These added features were then observed in high-resolution x-ray photoemission spectroscopy (XPS) experimental spectra from MnF 2 by Kowalczyk et A/., 3 and these results we reproduce in Fig. 1(b), together with the predicted heights and positions from the CI calculations, which are shown in Fig. 1(d). The calculated heights are derived here from the assumption that, at typical XPS excitation Units] ITY (Arb. 2 LU Z

Pressure-Induced High-Spin to Low-Spin Transition in FeS Evidenced by X-Ray Emission Spectroscopy

“…This simple picture also predicts that the energy separation between the two peaks is given by the product of the exchange integral J and (2S+1), where S is the total spin of the 3d shell; and that the intensity ratio between the two is given by S/(S+1) [18]. Both the energy splitting and intensity ratio are modified when configuration interaction is taken into account [19]. These calculations show that the 3p ↑ 3d ↑ final state is characterized by a single peak that constitutes most of the intensity of the main emission line.…”

Multiplet Fine Structure of the Gd and Tb 5P Levels

“…exchange interaction) with the electrons in unfilled subshells to form different final states. This effect has been well studied on filled s and p core levels of some transition metals and rare earth 4s, 5s, and 4f levels [15][16][17][21][22][23]. Most of multiplet studies have only considered the exchange interaction between the unpaired spins which results in two main features characterized by the hole spin parallel or anti-parallel to that of the unpaired electrons.…”

Effects of covalency on thep-shell photoemission of transition metals:MnO

“…[1][2][3][4][5][6][7][8][9][10][11][12] A principal concern has been the importance of interatomic as compared to intra-atomic effects. In order to treat many-body intra-atomic effects with reasonable accuracy, it is necessary that the wave function ͑WF͒ include the configuration mixing of nearly degenerate ͑ND͒ XPSforbidden configurations with the XPS-allowed configurations.…”

“…For MnO and other Mn 2+ ionic compounds, there is strong evidence and general agreement that CT configurations make, at most, a small contribution to the XPS spectra. 1,5,10,17,21 This minor role of CT configurations makes the theoretical study of MnO ideal to examine the impor-tance of other interatomic effects for the XPS spectra. In this paper, we report a study of these effects by comparing the results obtained with ab initio WF's for an isolated Mn 2+ cation and for an embedded MnO 6 cluster model of MnO with each other and with experiment.…”