Shulman G R, Yafet Y, Eisenberger P, Blumberg W E
Proc Natl Acad Sci U S A. 1976 May;73(5):1384-8. doi: 10.1073/pnas.73.5.1384.
X-ray absorption spectra near the Kalpha edge have been measured in various iron group compounds using the intense synchrotron radiation at the Stanford Synchrotron Research Project. In the cubic compounds KMF3 where M = Mn+2, Fe+2, Co+2, Ni+2, and Zn+2, well resolved lines were observed and assigned to the 1s leads to 3d, 1s leads to 4s, and 1s leads to 4p transitions. The observed energies agreed rather well with the spectroscopic energy levels of the Z + 1 ion and the intensities are shown to agree with those expected on the basis of one electron transitions of the form Z 1s2dn(L,S) leads to (Z + 1)1s2dnn'l'(L",S). The energies of the intense 1s leads to 4p transition increase by about 5 V going from KFeF3 to K2NaFeF6, but only by about 1 V from K4Fe(CN)6 to K3Fe(CN)6. The transitions confirm that upon oxidation of the hexacyanides the iron electronic structure barely changes. In the iron sulfur protein rubredoxin, where the iron is bound to a tetrahedron of sulfurs, the 1s leads to 3d transition was about seven times more intense than the same transition in an octahedrally coordinated compound. These intensities parallel those observed in the d-d transitions of optical spectra, because in both types of spectra the intensities depend upon 4p admixture. In the heme protein cytochrome c, upon oxidation the 1s leads to 4p transition shifts only about 1 V to higher energies similar to the iron hexacyanides. These results are discussed in terms of covalent bonding.
利用斯坦福同步辐射研究项目的强同步辐射，在各种铁族化合物中测量了Kα边附近的X射线吸收光谱。在立方化合物KMF3中，其中M = Mn²⁺、Fe²⁺、Co²⁺、Ni²⁺和Zn²⁺，观察到了分辨良好的谱线，并将其归属于1s到3d、1s到4s以及1s到4p跃迁。观测到的能量与Z + 1离子的光谱能级相当吻合，并且强度显示与基于形式为Z 1s²dn(L,S)到(Z + 1)1s²dnn'l'(L",S)的单电子跃迁所预期的强度一致。从KFeF3到K2NaFeF6，强的1s到4p跃迁的能量增加约5伏特，但从K4Fe(CN)6到K3Fe(CN)6仅增加约1伏特。这些跃迁证实，在六氰化物氧化时，铁的电子结构几乎没有变化。在铁硫蛋白铁氧化还原蛋白中，铁与硫的四面体相连，1s到3d跃迁的强度比在八面体配位化合物中的相同跃迁大约强七倍。这些强度与在光谱的d - d跃迁中观察到的强度平行，因为在这两种类型的光谱中，强度都取决于4p混合。在血红素蛋白细胞色素c中，氧化时1s到4p跃迁仅向更高能量移动约1伏特，类似于铁的六氰化物。根据共价键对这些结果进行了讨论。
