Zeeman effect

https://doi.org/10.1351/goldbook.Z06739
The splitting or shift of spectral lines due to the presence of an external magnetic field.
Sources:
Orange Book, 2nd ed., p. 122 [Terms]
PAC, 1996, 68, 2223. (Glossary of terms used in photochemistry (IUPAC Recommendations 1996)) on page 2284 [Terms] [Paper]