Photon Factory Activity Report 2004 #22 Part B (2005)
Electronic Structure of Condensed Matter

3B/2000G002, 2002G179

Valence-Band Satellites in Ni
Yasuo SAKISAKA*, Nobuo NAKAJIMA**, Hiroo KATO
Faculty of Science and Technology, Hirosaki University, Hirosaki 036-8561, Japan
Introduction
The photoelectron spectrum of Ni shows, besides theordinary 3d-band emission, an extra feature at ~6 eV
below the Fermi energy (EF). Following an original
suggestion by Mott, this 6-eV feature is generally
attributed to a many-body effect which leaves twocorrelated 3d holes. So far the 6-eV binding-energy twohole bound state has been intensively studied and its
8nature of atomically d multiplet structure was clarified.
81131Although he d multiplet structure has S, G, P, D, and3
1
3
1
F terms, the 6-eV satellite consists only of G, P, D, and3
1
F multiplets. The S state with a binding energy a few eVgreater than the 6-eV centroid was not clearly observed inNi. Its observation is necessary to confirm the Mott’sinterpretation.
We report an observation of the sharp d8 1S peak andabsence of three- and four-hole satellites in Ni [1].

measurements show that the d7 and d6 multiple-holesatellites do not exist or are very weak to be observed.
These d7 and d6 structures may be extrinsic and perhaps
due to artifacts of the subtraction procedures and /or someinelastic electron scattering, etc.

Experiment
The photoemission measurements were carried out at thebeamline BL-3B of the Photon Factory. The cleanNi(100) and Ni(111) surfaces, having sharp (1×1) LEED
patterns with low backgrounds, were prepared by+repeated cycles of Ar -ion sputtering and annealing. The
amounts of impurities were reduced to less than thedetection limit of Auger spectroscopy (e.g., the Augerpeak height ratio, O(KLL, 510eV)/Ni(LVV, 848eV), wasless than 1/400 and this corresponds to a coverage of0.003 monolayer or less).
Results, Discussion and Conclusion
Figure 1 shows a normal-emission spectrum of cleanNi(100) at hν =70 eV. A weak but fairly sharp peak isobserved at -9.3 eV is assigned to the 1S term of the d8multiplets.
The main 3d-line corresponds to the 3d hole screened
by a 3d electron, leading to the final-state configurationof 3d94s. The satellite corresponds to the two 3d holes,
which are localized on the same site, screened by 4s
electrons, leading to the final-state configuration of 3d84s2.
The 4s screening charge reduces the like-charge Coulomb
repulsion between the two 3d holes and glues the two 3dholes together to create a 3d8 long-lived bound state. Ourdata analysis suggests that the Slater-Condon Coulomb
integrals are reduced for the d8 satellite compared to theL3VV Auger processes and the 6-eV satellite state may
mix with the band states.
Three-hole (d7) and four-hole (d6) valence-bandsatellite features have been reported to be observed at~13.4, ~18, ~22, and ~27 eV below EF. However, our94

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Fig. 1. Normal-emission valence-band spectrum ofclean Ni(100) measured at hν =70 eV.
References[1] N. Nakajima, S. Hatta, J. Odagiri, H, Kato, andY. Sakisaka, Phys. Rev. B 70, 233103 (2004), andreferences therein.
* sakisaka@cc.hirosaki-u.ac.jp** Present address: Department of Physical Science,
Graduate School of Science, Hiroshima University,
Higashi-Hiroshima 739-8526, Japan.