Geant4 Simulations for the Radon Electric Dipole Moment Search at

Occupied
Orbitals
Fine
Structure
Hyperfine
Structure
Zeeman
Effect
2
P3/2
5p
F = 3
m
+3
F
2
P1/2
F = 2
_
3
_ 2
+ 2
D 1
D 2
F = 3
+ 3
5s
2
S1/2
F = 2
_ 3
_ 2
+ 2
Figure 2.4: Level diagram of 85 Rb (not drawn to scale).
(the selection rule for this process is ∆m = ±1 or 0 since the emitted photon can
have any polarization), only the m = −1/2 level can absorb the incident polarized
photons. The result is that the atoms become trapped in the m = +1/2 ground-state
level, this process is called “optical pumping” and can produce a very high degree of
polarization with almost all atoms occupying the m = +1/2 magnetic substate of the
1S 1/2 ground state.
Natural rubidium ( 85,87 Rb) vapour will be used in the RnEDM experiment to
polarize the radon nuclei through spin-exchange collisions. The occupied electronic
orbitals of the rubidium atom in its ground state are
1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 5s .
The first 36 electrons are in closed sub-shells which gives zero total angular momentum.
The valence electron in the 5s orbital behaves similarly to the above simplified
19