Paschen-Back effect

The Paschen - Back effect (after Friedrich Paschen and Ernst Back, who discovered it in 1921 ) describes the decoupling of spin and orbital angular momenta in the application of a strong magnetic field. A spectrum of anomalous Zeeman effect ( for atoms with total spin ) is thus in a spectrum beyond normal Zeeman effect ( for atoms with total spin ).

In "weak" magnetic fields, the spin angular momenta are due to the spin -orbit coupling initially added to a total spin and orbital angular momenta to a total orbital angular momentum:

The total spin angular momentum and the overall coupling then a total angular momentum precess about the axis of the applied field:

In "strong" [note 1] magnetic fields is the coupling of the magnetic moments of the applied field stronger than the spin -orbit coupling, so that the total spin and the total orbital angular momentum are no longer to couple, but precess independently about the axis of the applied magnetic field.

The energy splitting is now:

With

  • The gyromagnetic ratio
  • The reduced Planck constant
  • The magnetic flux density
  • Or the Landé factor for the orbital angular momentum and spin
  • Or the quantum number for the orbital angular momentum (also magnetic quantum number ) or spin.

Analogously, also occurs in the hyperfine structure splitting a Paschen - Back effect on: For sufficiently strong [note 2] magnetic fields is here broken the coupling of the total angular momentum and the nuclear spin to a new total angular momentum.

Comments

  • Quantum mechanics
  • Atomic physics
Energy level Ernst Emil Alexander Back
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