Nuclear & Particle Physics - Spin

The hypothesis that an electron possesses spin is qualitatively significant for the explanation of all the following topics EXCEPT the

A. Structure of the periodic table
B. Specific heat of metals
C. Anomalous Zeeman effect
D. Deflection of moving electron by a uniform magnetic field
E. Fine structure of atomic spectra

(GR8677 #27)

Solution:

(A) TRUE
Spin → Pauli exclusion principle → electron configuration → Structure of the periodic table

(B) TRUE
Specific heat for Fermions (½-integer spin) is different from Bosons (integer spin).

(C) TRUE
Zeeman Effect: the splitting of spectral lines when an external magnetic field is applied.
"Normal" Zeeman effect → This type of splitting is observed for spin 0 states since the spin does not contribute to the angular momentum.
"Anomalous" Zeeman effect → When electron spin is included, there is a greater variety of splitting patterns.

(D) FALSE
Deflection of moving electron by a uniform magnetic field does not depend on spin

(E) TRUE
Fine structure = the splitting of the spectral lines of atoms due to quantum mechanical (electron spin) and relativistic corrections.

Answer: D

Nuclear & Particle Physics - Zeeman Effect

The emission spectrum of an atomic gas in a magnetic field differs from that of the gas in the absence of a magnetic field. Which of the following is true of the phenomenon?

A. It is called the Stern-Gerlach effect
B. It is called the Stark effect
C. It is due primarily to the nuclear magnetic moment of the atoms
D. The number of emission lines observed for the gas in a magnetic field is always twice the number observed in the absence of a magnetic field.
E. The number of emission lines observed for the gas in a magnetic field is either greater than or equal to the number observed in the absence of a magnetic field

(GR8677 #82)

Solution:

Zeeman Effect: the splitting of a spectral line into several components in the presence of a static magnetic field.→ A and B are FALSE.

In most atoms, there exist several electron configurations with the same energy (degeneracy), so that transitions between these configurations and another correspond to a single spectral line.

The presence of a magnetic field breaks this degeneracy, since the magnetic field interacts differently with electrons with different quantum numbers, slightly modifying their energies. → C is FALSE.

The result is that, where there were several configurations with the same energy, they now have different energies, giving rise to several very close spectral lines.

image:  physics.cornell.edu (click image to enlarge)

→ E is TRUE as opposed to D

Answer: E