Stern-Gerlach experiment

Principle

A beam of potassium atoms generated in a hot furnace travels along a specific path in a magnetic two-wire field. Because of the magnetic moment of the potassium atoms, the non-homogeneity of the field applies a force at right angles to the direction of their motion. The potassium atoms are thereby deflected from their path. By measuring the density of the beam of particles in a plane of detection lying behind the magnetic field, it is possible to draw conclusions as to the magnitude and direction of the magnetic moment of the potassium atoms.

Tasks

1. Recording the distribution of the particle beam density in the detection plane in the absence of the effective magnetic field.
2. Fitting a curve consisting of a straight line, a parabola, and another straight line, to the experimentally determined special distribution of the particle beam density.
3. Determining the dependence of the particle beam density in the detection plane with different values of the non-homogeneity of the effective magnetic field.
4. Investigating the positions of the maxima of the particle beam density as a function of the non-homogeneity of the magnetic field.

Benefits

• Experience the essence of the Nobel Prize: Gerlach (1943)
• First proof of the quantization of the spatial orientation of the angular momentum
• A beam of neutral potassium atoms are deflected in a non homogeneous magnetic field and can even be measured precisely

Learning objectives

• Magnetic moment
• Bohr magneton
• Directional quantization
• g-factor
• Electron spin
• Atomic beam
• Maxwellian velocity distribution
• Two-wire field