Experimentelle Physik 4, Universität Würzburg, 97074 Würzburg, Germany.
J Phys Condens Matter. 2012 Jun 27;24(25):255602. doi: 10.1088/0953-8984/24/25/255602. Epub 2012 May 30.
We study the unoccupied electronic structure of the spin-1/2 quantum magnet TiOCl using x-ray absorption near-edge spectroscopy (XANES) at the Ti L and O K edges. We acquire data both in total electron and fluorescence yield modes (TEY and FY, respectively). While only the latter allows us to access the unconventional low-temperature spin-Peierls (SP) phase of TiOCl, the signal is found to suffer from significant self-absorption in this case. Nevertheless, we conclude from FY data that effects of the SP distortion on the electronic structure are absent in the incommensurate intermediate phase within experimental accuracy. The similarity of room-temperature FY and TEY data, the latter not being obscured by self-absorption, allows us to use TEY spectra for comparison with simulations. These are performed by means of cluster calculations in D(4h) and D(2h) symmetries using two different codes. We extract values of the crystal-field splitting and parameterize our results using the commonly seen notation of Slater, Racah and Butler. In all cases, good agreement with published values from other studies is found.
我们使用 X 射线吸收近边光谱（XANES）在 Ti L 和 O K 边缘研究了自旋 1/2 量子磁体 TiOCl 的未占据电子结构。我们分别在总电子和荧光产额模式（TEY 和 FY）下获取数据。虽然只有后者允许我们进入 TiOCl 的非常规低温自旋-佩尔斯（SP）相，但在这种情况下，发现信号受到严重的自吸收影响。然而，我们从 FY 数据中得出结论，在实验精度内，SP 畸变对电子结构的影响在非调谐中间相中不存在。室温 FY 和 TEY 数据的相似性，后者不受自吸收影响，使我们能够使用 TEY 光谱进行比较模拟。这些模拟是通过使用两种不同的代码在 D(4h)和 D(2h)对称性下的簇计算来进行的。我们提取了晶体场分裂的值，并使用常见的 Slater、Racah 和 Butler 符号对结果进行参数化。在所有情况下，都与其他研究的已发表值吻合良好。
