Nonaxial groups

The icosahedral group is the largest nonaxial group. An object with icosahedral... 

With respect to immobile chiroids, the appropriate symmetries are given by the familiar finite point groups C, (nonaxial), C (monoaxial), Dn (dihedral), T (tetrahedral), 0 (octahedral), and I (icosahedral). Molecules that belong to the first three groups are commonplace molecules with ground-state symmetries T [example tetrakis(trimethylsilyl)silane],39 O (example appoferritin 24-mer),40 and 1 (example human rhinovirus 60-mer),40 are relatively uncommon. 

With the exception of transition metal ions at a site with cubic symmetry, the ZFS often exceeds the electron Zeeman interaction at magnetic fields <1 T, sometimes even at the highest accessible fields (high-spin Fe(III)). In this situation, only the lowest lying doublet of spin states may be populated and only transitions within this doublet can be observed. It is convenient to describe such a doublet by an effective spin S = The ZFS of the group spin 5 > j then contributes to the effective g-ten-sor of the spin S = For example, X-band ESR spectra of high-spin Fe(III) in a situation with maximum nonaxiality of the ZFS (E = D/3) exhibit a sharp feature at g = 4.3. Note that unlike the normal g-tensor, the effective g-tensor may depend on the applied magnetic field. 

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