In spectroscopy, a rotation-reflection axis, which is a symmetry element such that rotation by
\(2\pi/n\) about the axis followed by reflection through a plane perpendicular to the axis transforms an object into itself.
Note:
In crystallography, a rotation-inversion axis, which is a symmetry element such that rotation by \(2\pi/n\) about the axis followed by inversion through the centre of symmetry transforms an object into itself.
Source:
PAC, 2021, 93, 647. 'Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)' on page 750 (https://doi.org/10.1515/pac-2019-0203)