Nuclear magnetic resonance

Nuclear magnetic resonance (NMR) is a special way to study tiny parts of atoms called nuclei. It happens when these nuclei are put inside a strong, steady magnetic field. When the nuclei get a gentle push from another changing magnetic field, they send out a signal. This signal has a special frequency that tells scientists a lot about the material.

NMR is used in many places. In chemistry, it helps scientists see how molecules are built. In hospitals, it helps doctors look inside the body without surgery. This is called magnetic resonance imaging (MRI). Some nuclei, like hydrogen-1 and carbon-13, are often studied because they are easy to see with NMR.

NMR works because some nuclei have a property called “nuclear spin.” This spin lets them act like tiny magnets. When they are in a magnetic field, they line up in certain ways. If they get a quick burst of radio frequency energy, they send out signals that scientists can read.

Strong magnetic fields make NMR work better. Very strong fields are often made using special superconducting magnets that are kept cold with liquid helium. These strong fields help scientists see more details. NMR can also be done with weaker fields, like the Earth’s magnetic field, for special tools such as magnetometers. In short, NMR is a very useful tool for science and medicine.

History

Nuclear magnetic resonance was first described in 1938 by Isidor Rabi. In 1946, Felix Bloch and Edward Mills Purcell used this idea with liquids and solids. They received a Nobel Prize in Physics in 1952 for their work.

Later, Russell H. Varian made the first NMR machine in 1952. NMR has become very helpful for scientists. It lets them study the structure of molecules. In the 2020s, a new type of NMR called zero- to ultralow-field nuclear magnetic resonance (ZULF NMR) was developed. This new NMR does not need very strong magnetic fields.

Theory of nuclear magnetic resonance

See also: Magnetic resonance (quantum mechanics)

All tiny particles called nucleons, which are neutrons and protons, that make up an atom’s nucleus have a special property called spin. This spin is like the nucleus spinning around.

If both the number of protons and neutrons in a nucleus are even, the total spin is zero. But if there’s an unpaired proton or neutron, the nucleus will have a spin. For example, the nucleus of deuterium, which is a type of hydrogen with one proton and one neutron, has a spin of 1.

A nucleus with spin also has a magnetic moment, which interacts with magnetic fields. This interaction allows scientists to observe signals in a technique called Nuclear Magnetic Resonance (NMR).

NMR is used to study the structure of molecules. It works by placing nuclei in a strong magnetic field and then disturbing them with a weak oscillating magnetic field. When the frequency of this disturbance matches the natural frequency of the nuclei, they absorb energy and then release it, creating a signal that can be measured.

Main article: Relaxation (NMR)

NMR spectroscopy

Main article: NMR spectroscopy

NMR spectroscopy is a helpful way to learn about molecules. It shows how atoms are connected and how they move in liquids and solids. By looking at the signals, scientists can find out the exact structure of a molecule. This helps in studying many different kinds of chemicals and materials.

NMR can also be used to build tiny computers and study how atoms interact. It works by measuring how tiny parts of atoms respond to magnetic fields, giving clues about their surroundings. This makes NMR a useful tool in chemistry and biology.

Applications

NMR is a very useful tool in many areas. In medicine, it helps doctors look inside the body without surgery using magnetic resonance imaging. Chemists use NMR to study and identify different chemicals. It can also measure things like the amount of water in food or check how well fluids flow in pipes.

In medicine, NMR is best known for magnetic resonance imaging, which helps doctors see inside the body. It is also used in research to study brain tumors and other body parts. NMR can show details about molecules by looking at how atoms behave in a magnetic field.

In chemistry, NMR helps scientists figure out the structure of molecules. It can tell them how atoms are arranged. This makes it very important for discovering new substances and checking that experiments worked correctly.

Makers of NMR equipment

Many companies make tools for studying nuclear magnetic resonance. Some of the biggest makers are Thermo Fisher Scientific, Magritek, Oxford Instruments, Bruker, Spinlock SRL, General Electric, JEOL, Kimble Chase, Philips, Siemens AG, and Agilent Technologies. Agilent Technologies also bought a company called Varian, Inc.. These companies help scientists learn about materials and molecules using special machines.