Fine structure in the quadrupolar transition of the Ho L 3 pre-edge observed by lifetime-broadening-suppressed XANES spectroscopy Hisashi Hayashi,* Masaki Kawata, Atsushi Sato, and Yasuo Udagawa IMRAM, Tohoku University, Katahira 2-1-1, Sendai 980-8577, Japan and PRESTO, JST, 4-1-8 Honcho Kawaguchi, Saitama, 332-0012, Japan Toshiya Inami and Kenji Ishii SRRC, JAERI, Mikazuki, Hyogo, 679-5148, Japan Haruhiko Ogasawara Department of Physics, Northern Illinois University, DeKalb, Illinois 60115, USA and APS, Argonne National Laboratory, 9700, South Cass Avenue, Illinois 60439, USA Susumu Nanao IIS, University of Tokyo, Komaba 4-6-1, Meguro, Tokyo 153-8505, Japan Received 28 December 2004; published 12 July 2005 The 2p3d resonant inelastic x-ray-scattering spectra of Ho 2 O 3 are measured under 0.7 eV resolution and analyzed in terms of an equation based on the Kramers-Heisenberg formula. Broadening due to core-hole lifetime 4.26 eV is completely suppressed to give sharp absorption bands with width of 0.5 eV together with energy position uncertainty 0.3 eV. Observed bands are assigned to be well-known 2p →4 f quadrupolar transitions that are otherwise buried under lifetime-broadened intense 2p →5d dipole transition. The present work opens up an opportunity to study 4 f -5d interactions more accurately. DOI: 10.1103/PhysRevB.72.045114 PACS numbers: 78.70.En, 61.10.Ht, 32.30.Rj It has been well known that L 3 x-ray-absorption near-edge structure L 3 -XANES is a direct probe of the electronic states in rare earth compounds. 1 The electronic structure of rare earth ions is governed by the interaction between elec- trons in the localized 4 f orbitals and those in the broad 5d band. In the L 3 -XANES spectra, dominated by the contributions from the dipole allowed E1 2p → 5d transition, quadrupolar E2 2p → 4 f transitions are expected to exist in the pre-edge region. Unfortunately, however, an inherent limitation due to core-hole lifetime broadening almost always prevents us from observing E2 transitions by x-ray-absorption spectros- copy. Hence in the recent years considerable efforts have been devoted to extract 2p → 4 f transition components from over- lapping 2p → 5d transitions. Hämäläinen et al. 2 observed pre-edge structure by measuring the 2p3d L resonant in- elastic x-ray scattering RIXS of DyNO 3  3 , where highly monochromatic incident x-ray energy is scanned across Dy L 3 edge while monitoring a narrow component of L emis- sion spectrum at a fixed energy. Bartolomé et al. 3,4 and Dallera et al. 5 tried to separate E2 transitions from dipolar ones by decomposition of a series of L RIXS spectra ob- tained with various excitation energies. Journel et al. 6 simu- lated observed weak RIXS features using a schematic repre- sentation of the densities of unoccupied states. Krisch et al. 7 attempted to distinguish E2 transitions by L RIXS excita- tion spectra where the energy transferred was kept constant. An elaborate deconvolution technique was also examined to extract the E2 component from high-quality conventional x-ray-absorption spectra. 8 Pre-edge E2 transitions are as im- portant as E1 transitions in x-ray-magnetic circular dichro- ism XMCD spectra. Accordingly various efforts have been reported to observe E2 transitions by the use of XMCD spectra. 9–15 Although these studies show that partial separation of E2 component is possible, none of them removes the core-hole lifetime broadening to accurately determine E2 transition en- ergies and intensities. If removed, because of multiplet na- ture of the 4 f states, the pre-edge is expected to show fine structures, which must provide us with much more detailed information about the 4 f -5d interactions. Here we show life- time broadening can be suppressed and fine structures in E2 transitions can be resolved by the analysis of, in principle, one high-resolution RIXS spectrum. In previous papers 16,17 we have proposed a procedure that can deduce lifetime-broadening-suppressed LBS-XANES spectra from 1s2p K RIXS spectra of Cu through numeri- cal analyses based on the Kramers-Heisenberg formula and have experimentally proved that LBS-XANES can, indeed, be retrieved. Subsequently, we have extended the approach to L RIXS spectra of DyNO 3  3 where final state effect arising from multiplet nature is significant 18 and have shown that a band due to 2p → 4 f quadrupole transitions is clearly separated from the tail of the intense white line. Because of a limited experimental resolution 1.4 eV, however, fine structures were not resolved. Theoretical RIXS spectra on several rare-earth compounds, where the effective resolu- tions are assumed to be 0.3 eV Refs. 19 and 20 or 0.7 eV, 21,22 are rich in fine structure. Hence with improved resolution, much more structured RIXS and, accordingly, higher-resolution LBS-XANES spectra leading to better un- PHYSICAL REVIEW B 72, 045114 2005 1098-0121/2005/724/0451145/$23.00 ©2005 The American Physical Society 045114-1