sudden polarization

https://dx.doi.org/10.1351/goldbook.ST07110
The occurrence of a large intramolecularcharge separation in the singlet excited state of polyenes and their derivatives twisted about a double bond. Non-symmetrical substitution or geometrical distortion is effective in polarizing the system. An example is the stabilization of the zwitterionic structure of 90° twisted ethene with one methylene group pyramidalized:
ST07110
Source:
PAC, 1999, 71, 1919 (Glossary of terms used in theoretical organic chemistry) on page 1964