Protons in certain atomic nuclei, when placed in a magnetic field, can be stimulated by radio waves of the correct frequency. Which particles are being stimulated?

Protons in certain atomic nuclei, when placed in a magnetic field, can be stimulated by radio waves of the correct frequency. Which particles are being stimulated?

• A. Electrons
• B. Protons in certain atomic nuclei
• C. Neutrons
• D. Photons

Answer: (B)

In a magnetic field, nuclei that have spin possess a magnetic moment and their spin states are split into energy levels. When radio-frequency radiation at the right frequency is applied, it can supply just the energy needed to flip those spins. This is nuclear magnetic resonance, and the particles being stimulated are protons inside certain atomic nuclei (such as hydrogen-1) because they have nonzero spin and a detectable magnetic moment. The required frequency, the Larmor frequency, depends on the field strength and the nucleus’s gyromagnetic ratio, setting the exact energy gap ΔE = h f that the RF photons deliver. Electrons, neutrons, or photons aren’t the targets in this specific nuclear spin resonance context, though electrons can undergo their own resonance at different frequencies and photons are the energy carriers, not the stimulated particles.

In a magnetic field, nuclei that have spin possess a magnetic moment and their spin states are split into energy levels. When radio-frequency radiation at the right frequency is applied, it can supply just the energy needed to flip those spins. This is nuclear magnetic resonance, and the particles being stimulated are protons inside certain atomic nuclei (such as hydrogen-1) because they have nonzero spin and a detectable magnetic moment. The required frequency, the Larmor frequency, depends on the field strength and the nucleus’s gyromagnetic ratio, setting the exact energy gap ΔE = h f that the RF photons deliver. Electrons, neutrons, or photons aren’t the targets in this specific nuclear spin resonance context, though electrons can undergo their own resonance at different frequencies and photons are the energy carriers, not the stimulated particles.