Resonant x-ray Raman scattering in BKα emission spectra of boron oxide (B2O3

Abstract

The satellite structure for the B Ka emission spectrum of boron oxide has been elucidated by threshold experiments carried out by varying the excitation energy of the incident undulator beam from below the B K absorption edge to several tens of eV above the absorption edge. Prominent emission of the satellite peak was observed when the excitation energy was tuned to the narrow pre-edge peak in the absorption spectrum, corresponding to the transition from BOs) to an unoccupied antibonding pn* orbital. It is concluded that the satellite peak originates from resonant x-ray Raman scattering due to a B(\s)-p7r*-B(\s _1 ) transition.PACS numbers: 78.70.EnRecently, several x-ray emission threshold studies have been investigated especially with respect to satellite structures associated with x-ray emission spectra using monochromatized synchrotron radiation [1][2][3][4]. Resonant Raman scattering was first observed by Sparks [5] from various metallic elements. Resonant emission has also been observed in the L regions of transition metals and their oxide compounds [6,7]. However, only a few attempts [8] have so far been made at the K region of low atomic number elements such as boron, carbon, and nitrogen, because of their low fluorescent yields and lack of the suitable excitation x rays in the VUV/soft-x-ray region.The B Ka emission spectra for boron and its related compounds have been investigated by many researchers with the use of high resolution x-ray emission spectroscopy [9-13]. Most of these spectra were obtained by either electron excitation or x-ray excitation using conventional x-ray sources. In the B Ka emission spectra of boron oxide (B2O3) and boron nitride (BN), satellite peaks are evident at both high-and low-energy sides of the main emission peak due to the B(2/?)-B(l^ _I ) transition. The nature of the low-energy satellites has recently been clarified and assigned to the transition from the molecular orbital with B(2/?) and Oils) or N(2 1 y) character to BOs _I ) core hole [14]. After the submission of this paper, O'Brien et al. [15] reported the excitation energy dependence of B Ka emission spectra of B2O3 and BN using monochromatized synchrotron radiation. They found that the main emission peaks and the low-energy satellites are shifted to lower energy when exciting into the core exciton states. For the high-energy satellites, Luck and Urch [16] observed that the high-energy satellite intensity of several boron oxide compounds correlates with the coordination number of boron. However, the nature of the high-energy satellites has not yet been clearly elucidated.The aim of this study is to investigate the satellite structures in the B Ka emission spectra of boron compounds using highly brilliant undulator radiation as an excitation source. In this paper, the origin of the highenergy satellite in the B Ka emission spectrum of B2O3 is described, which was elucidated by measuring selectively excited B Ka emission spectra using a quasimonochromatic or monochromatic undulator beam.Spectroscopic measurements o...

Characterization of buried thin films with resonant soft x-ray fluorescence

“…Although the valence band emission region is slightly different for cBN and hBN, by far the most striking difference is the sharp feature at 193 eV from hBN. Similar features arising from emission above E F have been detected in other resonant SXF work from boroncontaining systems such as B 3 O 2 9 . It results from the anomalous inelastic x-ray scattering effect first discovered by Sparks.…”

“…[5][6][7][8][9] A valence emission spectrum results from transitions from valence band states to the core hole produced by the incident photons. In the nonresonant energy regime, the excitation energy is far above the core binding energy, and the absorption and emission events are uncoupled.…”

Resonant soft-x-ray emission study in relation to the band structure of cBN

“…Recently, SXES studies have been performed by means of the inelastic-light-scattering process using high-brilliance synchrotron radiation as an excitation light source. [1][2][3][4][5][6][7][8] Using synchrotron radiation, one can utilize the excitation energy dependence of the SXES, which provides an experimental method to understand the electronic structure of matters in relation to the band structure.…”

“…[1][2][3][4][5][6][7] This is the resonant fluorescence or the inelastic lightscattering process, where the wave vector of the valence hole is the same as that of the excited electron. Thus, momentumresolved inelastic light scattering offers a band mapping technique.…”

Enhanced Resonant X-Ray Emissions of Mechanically Milled Hexagonal Boron Nitride in BoronK-Shell Excitation

“…The satellite structure in fluorescent x-ray emission spectra has recently been investigated by measuring selectively excited x-ray emission spectra [1][2][3][4]. We have demonstrated that the high-energy satellites in the B K x-ray emission spectra of boron oxide and boron nitride originate from resonant x-ray emissions due to an electron transition between boron 1s and unoccupied antibonding orbitals [5,6]. Prominent resonant x-ray emissions are observed in molecules with strongly localized unoccupied antibonding p ‫ء‬ orbitals, such as in boron atoms with threefold coordination.…”