The Racah seniority number (seniority quantum number)
was introduced by
Giulio Racah
Giulio (Yoel) Racah ( he, ג'וליו (יואל) רקח; February 9, 1909 – August 28, 1965) was an Italian–Israeli physicist and mathematician. He was Acting President of the Hebrew University of Jerusalem from 1961 to 1962.
The crater ...
for the classification of
electrons
The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family,
and are generally thought to be elementary particles because they have no ...
in an atomic configuration. The "seniority number", in a loosing statement, is
quantum number
In quantum physics and chemistry, quantum numbers describe values of conserved quantities in the dynamics of a quantum system. Quantum numbers correspond to eigenvalues of operators that commute with the Hamiltonian—quantities that can be kno ...
additional to the total angular momentum
and total spin
, which gives the degree of unpaired particles.
A spin-independent interaction
is assumed with the property
:
,
where
is the combined angular momentum,
magnetic quantum number,
is electrons' orbital angular momenta, and
is the dimensionless magnetic moment. The equation above shows there is no interaction unless the two electrons' orbital angular momenta are coupled to
. The eigenvalue is the "seniority number"
.
References
{{reflist
Quantum mechanics