Measure the Value of a Single Electron’s Magnetic Moment
Measure the Value of a Single Electron's Magnetic MomentThis experiment in modern physics investigates the intrinsic angular momentum of a particle - the fundamental property discovered by studying discrepancies between Bohr's quantum description of the hydrogen atom and experimental values. Designed by the renowned Physics department at Dartmouth College, this apparatus is an intriguing illustration of Uhlenbeck and Goudsmit's 1925 discovery.The elegant device generates a magnetic filed by a pair of Helmholtz coils powered by an AC current. A probe containing the parametric organic compound, diphrenyl-picri-hydrazyl (DPPH), and a wire coil are inserted into the field. DPPH has an unbound electron that orients in an external magnetic field. The electron spins like a top in the polarizing field with a frequency proportional to the magnitude of the field. If the polarizing magnetic field is swept through a range, the electron's precession varies in frequency with the field change. If students set up a weak high frequency field at right angles to the primary field, the weak field with interact with the electron when their frequencies are the same. When the probe containing DPPH is inserted into the field, a tiny coil, which provides the inductance for the oscillator, surrounds the crystals and supplies the transverse, high-frequency signal. The coil mounts in a sturdy metal probe with an acrylic end cap. Students can see the coil, but it is well protected. The probe is wired to an oscillator, which measures the electrons frequency as the magnetic field varies from positive to negative. The energy transfer values are then displayed on the oscillator's screen. Includes power supply, two Helmholtz coils, probe, electronics, and instructions. Requires an oscilloscope, available separately.