3. In geometry, an improper rotation, also
called rotoreflection or rotary reflection is, depending
on context, a linear transformation or affine
transformation which is the combination of
a rotation about an axis and a reflection in a plane
perpendicular to the axis.
In 3D, equivalently it is the combination of a rotation and
an inversion in a point on the axis. Therefore it is also
called a rotoinversion or rotary inversion.
What is Improper Rotation?
4. An improper rotation is performed by rotating the
molecule 360°/n followed by reflection through the
plane perpendicular to the rotation axis. If the
resulting configuration is indistinguishable from the
original, we say there exists an n-fold improper
rotation axis (or Sn axis) in the molecule
Formula of Improper Rotation (Sn): Cn + σh
What is Improper Rotation?