A nuclear isomer is a metastable or isomeric state of an atom caused by the excitation of a proton or neutron in its nucleus so that it requires a change in spin before it can release its extra energy. They decay to lower energy states of the nuclide through two isomeric transitions: Metastability is the ability of a non-equilibrium state to persist for a long period of time. ... Properties For alternative meanings see atom (disambiguation). ... Excitation is the amount of energy (energy in a general sense, not energy as defined in physics) that something or someone has. ... Properties In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... Properties In physics, the neutron is a subatomic particle with no net electric charge and a mass of 939. ... A stylized representation of a lithium atom. ... In physics, spin is an intrinsic angular momentum associated with microscopic particles. ... In physics, the decay mode describes a particular way a particle decays. ...

• γ (gamma) emission (emission of a high-energy photon)
• internal conversion (the energy is used to ionize the atom)

Contrast this with the definition of a chemical isomer, the more common use of the word. Also contrast with the meaning of isotope, in which the difference is the number of neutrons in the nucleus. Metastable isomers of a particular atom are usually designated with an "m" (or, in the case of atoms with more than one isomer, 2m, 3m, and so on). This designation is usually placed after the atomic symbol and number of the atom (e.g., Co-58m), but is sometimes placed as a superscript before (e.g., ^mCo-58 or ^58mCo). This article is about the nuclear process. ... In chemistry, isomers are molecules with the same chemical formula and often with the same kinds of bonds between atoms, but in which the atoms are arranged differently. ... Isotopes are forms of an element whose nuclei have the same atomic number–-the number of protons in the nucleus--but different atomic masses because the contain different numbers of neutrons. ...

Most nuclear isomers are very unstable, and radiate away the extra energy immediately (on the order of 10^-12 seconds). As a result, the term is usually restricted to mean isomers with half-lives of 10^-9 seconds or more. Quantum mechanics predicts that certain atomic species will possess isomers with unusually long lifetimes even by this stricter standard, and so have interesting properties. Fig. ...

The only stable nuclear isomer is Ta-180m, which occurs naturally in tantalum at about 1 part in 8300. Its half-life is at least 10¹⁵ years, and it may in fact be entirely stable. The origin of this isomer is mysterious, though it is believed to have something to do with supernovas. When it relaxes to its base state, it releases energetic photons with wavelength of 16 nanometers—x-ray wavelengths. There are reports that Ta-180m can be forced to release its energy by much weaker x-rays, but these are currently in scientific dispute. General Name, Symbol, Number tantalum, Ta, 73 Chemical series transition metals Group, Period, Block 5, 6, d Appearance gray blue Atomic mass 180. ... Remnant of Keplers Supernova, SN 1604. ... For the Science Fiction weapon, as seen in Star Trek, see Photon torpedo. ... To help compare different orders of magnitude this page lists lengths between 10 nm and 100 nm (10-8 and 10-7 m). ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... The wavelength is the distance between repeating units of a wave pattern. ...

Another reasonably stable nuclear isomer (with a half-life of 31 years) is hafnium-178m, which has the highest excitation energy of any stable isomer. One kilogram of pure Hf-178-2m contains approximately 900 megajoules of energy, or about a quarter of a kiloton of TNT. Further, all of the energy released is in gamma rays at 0.05 nanometers. As with Ta-180m, there are disputed reports that Hf-178-2m can be stimulated into releasing its energy, and as a result the substance is being studied as a possible source for gamma ray lasers. These reports also indicate that the energy is released very quickly, so that Hf-178-2m can produce extremely high powers (on the order of exawatts). As of 2005 the claims that hafnium isomers can be used as potential energy storage devices or even weapons is generally regarded with derision in the general scientific community and future prospects for the idea's vindication appear very dim. General Name, Symbol, Number hafnium, Hf, 72 Chemical series transition metals Group, Period, Block 4, 6, d Appearance gray steel Atomic mass 178. ... The international prototype, made of platinum-iridium, which is kept at the BIPM under conditions specified by the 1st CGPM in 1889. ... The joule (symbol J, also called newton meter, watt second, or coulomb volt) is the SI unit of energy and work. ... A megaton or megatonne is a unit of mass equal to 1,000,000 metric tons, i. ... This article is about electromagnetic radiation. ... Laser (US Air Force) A LASER (Light Amplification by Stimulated Emission of Radiation) is an optical device which uses a quantum mechanical effect called stimulated emission (discovered by Einstein while researching the photoelectric effect) in order to generate a coherent beam of light from a lasing medium of controlled purity... This page lists examples of the power in watts produced by various different sources of energy. ... 2005 is a common year starting on Saturday of the Gregorian calendar. ...

External links

• Research group which presented initial claims of hafnium nuclear isomer de-excitation control. - The Center for Quantum Electronics, The University of Texas at Dallas.

• Lengthy Washington Post article, March 2004

• May 2004 article in Physics Today which largely debunks the claims of the Texas research group.