PROBLEM 2. The Fine Structure of One-Electron Systems
a) The fine structure levels are characterized by the quantum number j. What are the j
values of a 5p electron? [1 pnt]
b) Briefly describe the physical mechanism that leads to the coupling of l and s. [2 pnts]
c) Consider the hypothetical case that l = 3 and s = 9/2.
What are the possible values of j? [2 pnts]
d) Back to the 5p electron. Calculate the energy of the fine structure levels with respect to the
unperturbed 5p energy. The fine structure constant A = 60 [cm^(-1)]. [1 pnt]
Hint: V_(SO) = (A)/(2)(j(j + 1) - l(l + 1) - s(s + 1)).
e) The shift of the j levels is asymmetric with respect to the "unperturbed" 5d binding energy. Show
that conservation of energy is not violated. [2 pnts]
f) Consider the upper, least bound j level. This system is put in an external magnetic field
B, sketch the behavior of the binding energies of the relevant m_(j) states as a function
of B. [2 pnts]
g) What happens if the external magnetic field becomes much stronger than the
internal magnetic field? [1 pnt]
h) Estimate the order of magnitude of the external magnetic field for which the fine
structure of the atom breaks down. [2 pnts]
Hint: g_(j) = 1 + (j(j + 1) - l(l + 1) + s(s + 1))/(2j(j + 1)) and μ_(B) = 0.47 [cm^(-1)/T]
PROBLEM 2. The Fine Structure of One-Electron Systems [3 pnts]
a) The fine structure levels are characterized by the quantum number j. What are the j
values of a 5p electron? [1 pnt]
b) Briefly describe the physical mechanism that leads to the coupling of l and s. [2 pnts]
c) Consider the hypothetical case that l = 3 and s = 9/2.
What are the possible values of j? [2 pnts]
d) Back to the 5p electron. Calculate the energy of the fine structure levels with respect to the
unperturbed 5p energy. The fine structure constant A = 60 [cm^(-1)]. [1 pnt]
Hint: Vso = (j(j + 1) - l(l + 1) - s(s + 1)).
e) The shift of the j levels is asymmetric with respect to the "unperturbed" 5d binding energy. Show
that conservation of energy is not violated. [2 pnts]
f) Consider the upper, least bound j level. This system is put in an external magnetic field
B, sketch the behavior of the binding energies of the relevant mj states as a function
of B. [2 pnts]
g) What happens if the external magnetic field becomes much stronger than the
internal magnetic field? [1 pnt]
h) Estimate the order of magnitude of the external magnetic field for which the fine
structure of the atom breaks down. [2 pnts]
and g = 0.47 [cm^(-1)/T]
2j(j + 1)