Nuclear isomer

Nuclear isomer refers to an excited state of an atomic nucleus in which the nucleus has higher energy than its ground state. These isomers are metastable and can exist for a significantly longer period than the typical timescales associated with nuclear transitions. Nuclear isomers differ from other excited nuclear states in their ability to remain in their excited state for times ranging from microseconds to years before emitting gamma radiation or undergoing internal conversion and returning to the ground state.

Characteristics

Nuclear isomers are characterized by their half-life, energy, and mode of decay. The half-life of a nuclear isomer can vary widely, from extremely short periods to timescales that exceed the age of the universe. The energy level of the isomer state is higher than the ground state but lower than that of other excited nuclear states that decay more rapidly. Decay modes for nuclear isomers include gamma decay, where the nucleus releases energy in the form of gamma rays, and internal conversion, which involves the direct transfer of energy to an electron, causing its ejection from the atom.

Formation

Nuclear isomers are formed through nuclear reactions such as neutron capture, heavy ion collisions, and beta decay. In these processes, the nucleus absorbs energy and particles, leading to an excited state. If the configuration of the nucleons (protons and neutrons) in this excited state is such that the transition to a lower energy state is hindered by quantum mechanical rules, the nucleus can become trapped in a metastable state, thus forming a nuclear isomer.

Applications

Nuclear isomers have applications in various fields, including medicine, where they are used in diagnostic imaging and radiation therapy. In nuclear physics, isomers are used to study the properties of atomic nuclei and the forces that hold them together. Additionally, there is ongoing research into the potential use of nuclear isomers as a source of stored energy, which could be released on demand to power nuclear batteries.

Notable Examples

One of the most well-known nuclear isomers is Technetium-99m (Tc
_99m ), widely used in medical diagnostic imaging. Another example is Hafnium-178m2 (Hf
_178m2 ), which has attracted interest due to its potential for use in nuclear batteries.

See Also

• Nuclear physics
• Gamma ray
• Internal conversion
• Neutron capture
• Beta decay