The lowest-energy nuclear isomer known: https://en.wikipedia.org/wiki/Isotopes_of_thorium#Thorium-229m
"Gamma ray spectroscopy has indicated that 229Th has a nuclear isomer 229mTh with a remarkably low excitation energy. This would make it the lowest-energy nuclear isomer known, and it might be possible to excite this nuclear state using lasers with wavelengths in the vacuum ultraviolet. The isomer might have application for high density energy storage,[10] an accurate clock,[11] as a qubit for quantum computing, or to test the effect of the chemical environment on nuclear decay rates.[12] The lifetime of the isomer has been measured to be 6±1 hours. The measurement was done by collecting recoiled 229mTh atoms in a MgFs crystal and measuring the light emission variation over time.[13] If this isomer were to decay it would produce a gamma ray (defined by its origin, not its wavelength) in the ultraviolet range." Harry On Mon, Jan 18, 2016 at 10:47 AM, Bob Cook <frobertc...@hotmail.com> wrote: > Eric-- > > I did misunderstand what I thought you were saying. > > I do agree with you that most people consider nuclear isomers to be > excited energy states with a large differential energy above the ground > state. > > I have always considered any excited nuclear state to be a nuclear > isomer. I do not know what the elevated energy nuclear state which is due > to spin energy as established during an NMR energy addition would be > called. I think it fits the general definition of an excited state with a > lifetime less than 10-9 sec., and, thus, it is not metastable from that > standpoint. As you point out normal NMR states are not at a large energy > differential, except in large magnetic fields. The larger the field, the > greater the excited energy is above the ground state. I think that the > rule is that the changes in spin angular momentum have to be prime number > multiples of the h/2-pie quantum of angular momentum. The energy of the > elevated state results from the change of the nuclear spin magnetic moment > in the ambient B magnetic field. > > Bob Cook > > > *From:* Eric Walker <eric.wal...@gmail.com> > *Sent:* Sunday, January 17, 2016 10:20 AM > *To:* vortex-l@eskimo.com > *Subject:* Re: [Vo]:Re: Nuclear Isomers (2005 article in Nature) > > Hi Bob, > > On Sun, Jan 17, 2016 at 7:15 AM, Bob Cook <frobertc...@hotmail.com> wrote: > > I agree with your thought about the role of isomers in the natural >> abundance of elements. > > > I think you accidentally mistook the quote I was quoting from Harry's > article for something I myself said. I was asking for clarification of what > they were saying. > > Isomers are what makes nuclear magnetic resonance (NMR) a valuable tool. >> The idea is that a nucleus is excited to an elevated “isomeric” energy >> state by a RESONANT radio frequency input energy in a magnetic field and >> then decays back to its initial “ground state'’ or some other ground state >> not the same as the original state. > > > Forgive my ignorance -- when we talk about NMR, I think of polarization of > nuclei with nonzero spin in an external field using radiowaves or > microwaves. When I think of an isomer, I think of a nuclear isomer, in > which the nucleons in a nucleus are in a configuration that lies keV or MeV > above the ground state. I don't think radiowaves or microwaves can do > anything to populate or depopulate these states; or am I mistaken? > > A question I have about the nuclear isomerism referred to in the opinion > piece has to do with its potential utility. It seems like it would at best > be good as a battery, or, possibly, a bomb. > > Eric >
