Excitation of Core Electrons

The original table [19] contains even more absorption features. - E = 189.67 [8], leading to the reported T value. - T = 4.49 eV [8]. - T values given for excitation of 2p3,2 [18]. 

Selected values of the adiabatic (ad) ionization potential of the outer-valence orbital Sa from different methods of measurement are given in order of increasing magnitude In the table below (PES = photoelectron spectroscopy, PIMS = photoionization mass spectrometry, also simulated by dipole (e, e+lon) spectroscopy, PA = photoabsorption). Other adiabatic and the vertical (vert) values for 5a and values for the other outer-valence orbital 2e are reported in separate sections on PES (also simulated by binary (e, 2e) spectroscopy) and MS work added to the table  

He I radiation. - He and Ar continua and hydrogen pseudocontinuum. - Monoenergetic electrons. Synchrotron radiation. Ej = 9.97 eV was given in [6]. Electron impact energy was 8 keV. 

PES work yielded the following adiabatic and vertical ionization potentials for the outer-valence orbitals  

See also the preceding table. - For the vertical values, see also [12]. - Adiabatic values apparently taken from [9]. PE spectra of the group V (N through Sb) hydrides and halogenides were compared [8]. - Ej(5ai ad)=9.98 earlier given in [13]. - Ej(5ai ad) was questioned [10] in view of the lower value (9.98 eV) given earlier [13] see also [4]. - The angular distribution parameter p was measured [11], see also [14]. 

---

Inelastic scattering processes are not used for structural studies in TEM and STEM. Instead, the signal from inelastic scattering is used to probe the electron-chemical environment by interpreting the specific excitation of core electrons or valence electrons. Therefore, inelastic excitation spectra are exploited for analytical EM. 

XAS data comprises both absorption edge structure and extended x-ray absorption fine structure (EXAFS). The application of XAS to systems of chemical interest has been well reviewed (4 5). Briefly, the structure superimposed on the x-ray absorption edge results from the excitation of core-electrons into high-lying vacant orbitals (, ] ) and into continuum states (8 9). The shape and intensity of the edge structure can frequently be used to determine information about the symmetry of the absorbing site. For example, the ls+3d transition in first-row transition metals is dipole forbidden in a centrosymmetric environment. In a non-centrosymmetric environment the admixture of 3d and 4p orbitals can give intensity to this transition. This has been observed, for example, in a study of the iron-sulfur protein rubredoxin, where the iron is tetrahedrally coordinated to four sulfur atoms (6). 

X-ray absorption near edge structure (XANES) The X-ray absorption spectrum, as for EXAFS, may also show detailed structure below the absorption edge. This arises from excitation of core electrons to high level vacant orbitals, and can be used to estimate the oxidation state of the metal ion. 

---