Experiments to Control Atom Number and Phase-Space Density in ...

Property Symbol Value Reference
Atomic numer Z 3
Nucleons Z+N 6
Natural abundance η 7.6% [15]
Atomic mass m 6.0151214 u [21]
9.9883414×10 −27 kg
Nuclear spin I 1
Electronic spin S 1/2
Table 2.2: Physical properties of 6 Li
2.3 Fine and Hyperfine Structure
Even in the absence of any external electromagnetic fields, interactions between
the subatomic particles within the atoms will give rise to a splitting of the energy levels.
Relativistic energy corrections, spin-orbit coupling and the Darwin term give rise to
the fine-structure. The interaction between the nuclear spin I and the electron angular
momentum J leads to the hyperfine structure. More detail on these interactions is given
in the following sections.
2.3.1 Fine Structure
Alkali atoms have a single unpaired electron in the valence shell. The ground
and first excited state configurations for lithium are 1s 2 2s 1 and 1s 2 2p 1 respectively. For
rubidium the ground state configuration is [Kr]5s 1 and [Kr]5p 1 describes the excited
state. The transition between these two states is usually called the D-line. This is
the energy level structure one derives from the central potential (spin-independent)
approximation.
Relativistic energy corrections, spin-orbit coupling, and the Darwin term lead
to an energy splitting called fine-structure. The Hamiltonian describing the interaction
between the orbital angular momentum L and the spin angular momentum S can be
written as [22–25]
Hfs = A L· S, (2.4)
where A is the constant parameterizing the strength of the interaction. The coupling
6