zero field splitting

https://doi.org/10.1351/goldbook.Z06741
The separation of multiplet sublevels in the absence of an external magnetic field.
Source:
PAC, 1996, 68, 2223. 'Glossary of terms used in photochemistry (IUPAC Recommendations 1996)' on page 2284 (https://doi.org/10.1351/pac199668122223)