Example 1 : Oxidation States of Titanium
Titanium exhibits very large chemical shifts between different oxidation states of the metal; in the diagram below a Ti 2p spectrum from the pure metal (Tio ) is compared with a spectrum of titanium dioxide (Ti4+ ).
(i) the two spin orbit components exhibit the same chemical shift (∼ 4.6 eV);
(ii) metals are often characterised by an asymmetric line shape, with the peak tailing to higher binding energy' whilst insulating oxides give rise to a more symmetric peak profile;
(iii) the weak peak at ca. 450.7 eV in the lower spectrum arises because typical x-ray sources also emit some x-rays of a slightly higher photon energy than the main Mg Kα line; this satellite peak is a "ghost" of the main 2p3/2 peak arising from ionisation by these additional x-rays.