/pah"sheuhn bahk"/ , Physics.
a splitting of spectral lines observed when the source of a radiation is subjected to a strong magnetic field, caused when the vectors associated with the spin and orbital angular momentum exhibit individual rather than common precession. Cf. Zeeman effect .
[ 1920-25; named after Friedrich Paschen (1865-1947) and Ernst Back (1881-1959), German physicists ]