Conventions symmetry species labels

The symmetry species labels are conventional A and B indicate symmetry or antisymmetry, respectively, to C2, and the subscripts 1 and 2 indicate symmetry or antisymmetry, respectively, to n (xz). 

If the molecular plane of H20 had been designated the xz plane rather than the yz plane, then the symmetry species of the v3 vibration would be bx rather than b2. Of course, the labeling of the plane is arbitrary, but standard conventions have been agreed on for most molecules.7... 

The electron Zeeman effect arises from the interaction of unpaired electrons with the external magnetic field and determines the position at which resonance occurs [i.e., the deviation of the g-factor from the free electron value (g = 2.00232)]. Species with axial symmetry, such as Cu2+ and V " " (i.e., with one principal axis of symmetry, conventionally the z-axis, and equivalent x> and y-axes), exhibit two g-values, usually labeled gy = i.e., the g-value along... 

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