Re: [Vo]:Nuclear Isomers (2005 article in Nature)
Another link about isomers http://www.iisc.ernet.in/currsci/sept25/articles9.htm Quote: "Recently, there has been renewed interest in the study of isomers, with the prospects of realizing enormous amount of stored energy in nuclei through the accelerated decay of isomer. If one has to manipulate the isomer to deexcite on a faster time scale, then it is essential to have a better understanding of nuclear structure of not only the isomer but also the neighbouring excited states. In principle, low energy (eV–keV) photons should be able to initiate an accelerated decay of isomer either by stimulated emission to a nearby lower energy state or absorption to a nearby higher energy state. In essence, the meta-stable state can be made to shed its stored energy on a faster timescale, resulting in considerable energy gain. " Harry On Fri, Jan 15, 2016 at 5:25 PM, H Veeder wrote: > Nuclear physics: Long live isomer research > > Excited quantum states in nature are normally extremely short-lived, and > this certainly applies to most nuclei. But what makes the metastable > nuclear states different? And how can we exploit them for useful > applications? > > Introduction > > An isomer is an excited quantum-mechanical state of a nucleus, in which a > combination of nuclear structure effects inhibits its decay and endows the > isomeric state with a lifetime that is longer than expected (some examples > are shown in Table 1). The strong force that binds a nucleus together and > the exchange of the mediators of this force lead to immeasurably short > lifetimes of the order of 10 > ^ > -24 s for most nuclear states. But known isomers in nuclei span the entire > range of lifetimes from 10 > ^ > 15 years for 180mTa (m = metastable) — longer than the accepted age of the > universe — to an informal rule of thumb on the lower side of approximately > 1 ns. This inhibition to decay leads to the storage of enormous amounts of > energy in these states (10 > ^ > 4 or 10 > ^ > 5 times more than chemical energy release). The challenge and potential > for scientific discovery today lie in the understanding of the formation of > nuclear isomers (through a better comprehension of nuclear structure), the > ability to excite and de-excite isomers at will for a broad range of > applications from isomeric bombs to a clean source of energy, and the > exploration of nuclei with isomeric states in nuclear astrophysics to > determine how they affect the creation of the elements in the universe, and > how they eventually contribute to the makeup of life in our cosmos. > > continues... > > http://www.nature.com/nphys/journal/v1/n2/full/nphys150.html >
Re: [Vo]:Nuclear Isomers (2005 article in Nature)
In reply to Eric Walker's message of Fri, 15 Jan 2016 19:06:51 -0600: Hi, [snip] >The opinion piece says this: > >Finally, isomers play a significant role in determining the abundances of >> the elements in the universe. In hot astrophysical environments, an >> isomeric state can communicate with its ground state through thermal >> excitations. This could alter significantly the elemental abundances >> produced in nucleosynthesis. > > >Is anyone able to elaborate on what is being alluded to here? > >Eric I would guess that in "hot astrophysical environments" occasionally sufficient energy is available to raise the metastable isotope to a higher energy level from which it can then decay rapidly. Regards, Robin van Spaandonk http://rvanspaa.freehostia.com/project.html
Re: [Vo]:Nuclear Isomers (2005 article in Nature)
The opinion piece says this: Finally, isomers play a significant role in determining the abundances of > the elements in the universe. In hot astrophysical environments, an > isomeric state can communicate with its ground state through thermal > excitations. This could alter significantly the elemental abundances > produced in nucleosynthesis. Is anyone able to elaborate on what is being alluded to here? Eric
[Vo]:Nuclear Isomers (2005 article in Nature)
Nuclear physics: Long live isomer research Excited quantum states in nature are normally extremely short-lived, and this certainly applies to most nuclei. But what makes the metastable nuclear states different? And how can we exploit them for useful applications? Introduction An isomer is an excited quantum-mechanical state of a nucleus, in which a combination of nuclear structure effects inhibits its decay and endows the isomeric state with a lifetime that is longer than expected (some examples are shown in Table 1). The strong force that binds a nucleus together and the exchange of the mediators of this force lead to immeasurably short lifetimes of the order of 10 ^ -24 s for most nuclear states. But known isomers in nuclei span the entire range of lifetimes from 10 ^ 15 years for 180mTa (m = metastable) — longer than the accepted age of the universe — to an informal rule of thumb on the lower side of approximately 1 ns. This inhibition to decay leads to the storage of enormous amounts of energy in these states (10 ^ 4 or 10 ^ 5 times more than chemical energy release). The challenge and potential for scientific discovery today lie in the understanding of the formation of nuclear isomers (through a better comprehension of nuclear structure), the ability to excite and de-excite isomers at will for a broad range of applications from isomeric bombs to a clean source of energy, and the exploration of nuclei with isomeric states in nuclear astrophysics to determine how they affect the creation of the elements in the universe, and how they eventually contribute to the makeup of life in our cosmos. continues... http://www.nature.com/nphys/journal/v1/n2/full/nphys150.html
