Optical Spectra of Materials
Kitsakorn Locharoenrat · 2016
Figure 13.4 Hydrogen atom showing all degenerate states. Second, in the case of a heavy atom with atomic number Z more than 30, the LS coupling scheme becomes worse approximation. The splitting by J value is small for small atomic numbers, so they are called fine structures. This splitting becomes large for large atomic numbers, and they are no longer fine structures. It is more appropriate if we specify the terms by jiŸ of i electrons, because the splitting by J becomes larger. Such a way of specification of electronic configuration is called JJ coupling. Then we can specify the electronic states by the total angular momentum of one electron as j l si i i = + (13.10)and we get the total angular momentum of i electrons as J ji =Â (13.11) In addition to the spin-orbit interaction, the crystal field or the electric field induced by neighboring ions also affects the electronic states of the local electron system. The Hamiltonian of this effect is H H H V = + +0 SO crystal (13.12) For example, lanthanide ions have H V SO crystal>> , while transition metals have H V SO crystal<< . 13.3 Optical Spectra of MoleculesThe vibrational and rotational spectra of the molecules are seen under the infrared region 400-4000 cm−1 (Fig. 13.5).