0198506961.pdf

6.1 Hyperfine structure 103

Na,Z=11 Cs,Z=55

E(3p^2 P 3 / 2 )−E(3p^2 P 1 / 2 ), E(6p^2 P 3 / 2 )−E(6p^2 P 1 / 2 ),

∆fFS= 510 GHz ∆fFS= 16 600 GHz

For the ground state 3s^2 S 1 / 2 , For the ground state 6s^2 S 1 / 2 ,

∆fHFS=1.8GHz ∆fHFS=9.2GHz

For 3p^2 P 1 / 2 , For 6p^2 P 1 / 2 ,

∆fHFS=0.18 GHz ∆fHFS=1.2GHz

The hyperfine splitting of the ground states and the fine-structure
splitting of the first excited states are indicated on the plot of energies
againstZin Fig. 6.5. The values shown are only a guideline; e.g. different

Energy (eV)

1

H

H

He

He

Na

Na

Mg

Mg

Cs

Cs

Hg

Hg

10 100

1

10

102

10 −^1

10 −^2

10 −^3

10 −^4

10 −^5

10 −^6

Fine structure (first excited state)

Gross structure

Residual electrostatic energy

Hyperfine structure (ground state)

Fig. 6.5A logarithmic plot of the

energy of various structures against

atomic numberZ; the hyperfine split-

ting of the ground state is plotted with

data from Fig. 5.7. All the points are

close to the maximum values of that

quantity for low-lying configurations,

terms, levels and hyperfine levels (as

appropriate) of neutral atoms with one

or two valence electrons, and these il-

lustrate how these quantities vary with

Z. This is only a rough guideline in

particular cases; higher-lying configura-

tions in neutral atoms have smaller val-

ues and in highly-ionized systems the

structures have higher energies.