Nuclear magnetism
Nuclear magnetism refers to the magnetic properties of an atomic nucleus, which acts as a tiny magnet due to the spin of its protons and neutrons. This phenomenon is the basis for the widely used analytical technique known as Nuclear Magnetic Resonance (NMR) and the medical imaging technique Magnetic Resonance Imaging (MRI), where a strong magnetic field is used to align these nuclear magnets and a radio frequency pulse is applied to excite them. The subsequent release of energy is measured to provide detailed information about molecular structure and composition.
How it works
- Certain atomic nuclei with an odd mass or atomic number have a property called "nuclear spin".
- As a charged particle in motion, a spinning nucleus generates a magnetic field, effectively behaving like a small bar magnet with a north and south pole. This is the nuclear magnetic moment.
- When placed in a strong external magnetic field, these nuclear magnets will align in a specific direction.
- A pulse of radio frequency energy is then used to "kick" these aligned nuclei out of their alignment.
- When the radiofrequency pulse is turned off, the nuclei return to their original alignment, re-emitting energy at a specific frequency. This "resonance frequency" is unique to the nucleus's chemical environment.
- By detecting and analyzing the specific frequencies emitted, scientists can determine the structure of a molecule or create detailed images of tissues.
