High Spin Suppression of Decay
The most common mechanism for suppression of gamma decay of excited nuclei, and thus the existence of a metastable isomer for the nucleus, is lack of a decay route for the excited state that will change nuclear angular momentum (along any given direction) by the most common amount of 1 quantum unit of spin angular momentum. Such a change is necessary to emit a gamma photon, which has a spin of 1 unit in this system. Integral changes of 2,3,4, and more units in angular momentum are possible (the emitted photons carry off the additional angular momentum), but changes of more than 1 unit are inhibited by about 5 orders of magnitude in rate for every additional unit of spin change larger than 1, that the emitted gamma ray must carry. The highest known spin change of 8 units occurs in the decay of Ta-180m, which suppresses its decay by a factor of 1035 from that associated with 1 unit, so that instead of a natural gamma decay half life of 10−12 seconds, it has a half life of more than 1023 seconds, or at least 3 x 1015 years, and thus has yet to be observed to decay.
Read more about this topic: Nuclear Isomer
Famous quotes containing the words high, spin, suppression and/or decay:
“High on a throne of royal state, which far
Outshone the wealth of Ormus and of Ind,
Or where the gorgeous East with richest hand
Show’rs on her kings barbaric pearl and gold,
Satan exalted sat, by merit raised
To that bad eminence; and, from despair
Thus high uplifted beyond hope, aspires
Beyond thus high, insatiate to pursue
Vain war with Heav’n, and by success untaught,
His proud imaginations”
—John Milton (1608–1674)
“In tragic life, God wot,
No villain need be! Passions spin the plot:
We are betrayed by what is false within.”
—George Meredith (1828–1909)
“Fashion required the suppression of all naturalness—’to walk upright, with unbending joints; to shake hands after the pump- handle formula; to look inexpressibly indifferent towards everybody and everything; and speak only in a mincing voice was to be a decorous member of society.’”
—For the State of Rhode Island, U.S. public relief program (1935-1943)
“Now, a corpse, poor thing, is an untouchable and the process of decay is, of all pieces of bad manners, the vulgarest imaginable. For a corpse is, by definition, a person absolutely devoid of savoir vivre.”
—Aldous Huxley (1894–1963)