Electronic transitions term symbols

The preceding results can be compared with the selection rules for all the possible electronic transitions obtained from group theory, to give electronic assignments (term symbols) for each of the luminescence bands. The resulting electronic assignments are A2 and A2u for the HE and LE bands, respectively. A discussion of the concepts of group theory that lead... 

The progression of sections leads the reader from the principles of quantum mechanics and several model problems which illustrate these principles and relate to chemical phenomena, through atomic and molecular orbitals, N-electron configurations, states, and term symbols, vibrational and rotational energy levels, photon-induced transitions among various levels, and eventually to computational techniques for treating chemical bonding and reactivity. 

Most complexes showing spin-state transitions are in fact of low symmetry. In order to describe their electronic structure it is convenient to employ term symbols appropriate to cubic symmetry and this practice will be followed below. The most common transition-metal ions for which spin-state transitions have been observed are Fe " (3d ), Fe " (3d ) and Co (3d ), a minor role being played by Co " (3d ), Mn " (3d ), as well as Cr " and Mn " (3d ). The relevant ground states for an octahedral disposition of the ligands are LS Ui,(t ,) and HS r2,(t ,e ) for iron(II), LS and HS Ai,(t, e ) for... 

In the case of optical processes involving electronic states which participate in the chemical bonding, the nature of the bonding (covalent, ionic) and the symmetry of the site at which the emitting ion is incorporated play a very important role. This is generally described by ligand field theory, which is not treated here. However, the term symbols for the description of the electronic transitions will be used. 

For labelling the states of an electronic transition spectral term symbols are used in the form where F is the upper-case version of the symmetry species... 

The term symbols B, and were confirmed by rotational analyses, which yielded a type-C character of the observed electronic transition [8,17,18], see also a preliminary statement in [11]. 

With reference to the F, Z), P, and 5 terms of a d configuration, explain how you can use term symbols to gain information about allowed electronic transitions. 

The Tanabe-Sugano diagram for a d ion is shown in Figure 17.27. For the HS complex at 293 K, the ground-state term symbol is Tjg and there is only one spin-allowed transition (to the Eg ES). The GS term symbol for LS Fe(ll) is A g and several spin-allowed transitions to low-lying excited states are possible. The absorption bands for [Fe(ptz)g](BF4)2 at 293 K and at 20 K are listed in Table 17.19 along with their assigned electronic transitions. 

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