Help


[permalink] [id link]
+
Page "Americium" ¶ 10
from Wikipedia
Edit
Promote Demote Fragment Fix

Some Related Sentences

half-life and decay
Naturally occurring with a half-life of 1. 25 years, decays to stable ( 11. 2 %) by electron capture or positron emission, and also to stable ( 88. 8 %) via beta decay.
It decays by emission of a α-particle to < sup > 237 </ sup > Np ; the half-life of this decay was first determined as 510 ± 20 years but then corrected to 432. 2 years.
Gamow solved a model potential for the nucleus and derived, from first principles, a relationship between the half-life of the decay, and the energy of the emission, which had been previously discovered empirically, and was known as the Geiger – Nuttall law.
For example, at over 1. 9 years, over a billion times longer than the current estimated age of the universe, bismuth-209 ( atomic number 83 ) has the longest known alpha decay half-life of any naturally occurring element.
For example, at over 1. 9 years, over a billion times longer than the current estimated age of the universe, bismuth-209 ( atomic number 83 ) has the longest known alpha decay half-life of any naturally occurring element.
The two natural radioactive isotopes are < sup > 113 </ sup > Cd ( beta decay, half-life is 7. 7 × 10 < sup > 15 </ sup > years ) and < sup > 116 </ sup > Cd ( two-neutrino double beta decay, half-life is 2. 9 × 10 < sup > 19 </ sup > years ).
The other three are < sup > 106 </ sup > Cd, < sup > 108 </ sup > Cd ( both double electron capture ), and < sup > 114 </ sup > Cd ( double beta decay ); only lower limits on their half-life times have been set.
These are all considered stable, although < sup > 156 </ sup > Dy decays by alpha decay with a half-life of over 1 × 10 < sup > 18 </ sup > years.
The least stable is < sup > 138 </ sup > Dy with a half-life of 200 ms. Isotopes that are lighter than the stable isotopes tend to decay primarily by β < sup >+</ sup > decay, while those that are heavier tend to decay by β < sup >−</ sup > decay, with some exceptions.
published a convincing synthesis of < sup > 260 </ sup > Db in the reaction between californium-249 target and nitrogen-15 ions and measured the alpha decay of < sup > 260 </ sup > Db with a half-life of 1. 6 seconds and a decay energy of 9. 10 MeV, correlated with the daughter decay of lawrencium-256:
While < sup > 153 </ sup > Eu is stable, < sup > 151 </ sup > Eu was recently found to be unstable to alpha decay with half-life of, giving about 1 alpha decay per two minutes in every kilogram of natural europium.
The predicted double beta decay of < sup > 160 </ sup > Gd has never been observed ( the only lower limit on its half-life of more than 1. 3 × 10 < sup > 21 </ sup > years has been set experimentally < ref name =" DBD ">).
Retrieved on 2008-03-01 </ ref > It was reported that this isotope decayed by emission of an alpha-particle with an energy of 8. 83 MeV and a projected half-life of ~ 22 s, assuming a 0 < sup >+</ sup > to 0 < sup >+</ sup > ground state decay to < sup > 266 </ sup > Sg using the Viola-Seaborg equation.
Out of this two, indium-115 makes up 95. 7 % of all indium but it is radioactive, decaying to tin-115 via beta decay with half-life of 4. 41 years, four orders of magnitude larger than the age of the universe and nearly 50, 000 times longer than that of natural thorium.
All its isotopes except for lawrencium-260 ,-261 and-262 decay with a half-life of less than a minute.

half-life and was
It was produced by the capture of 15 neutrons by uranium-238 nuclei followed by seven beta-decays, and had a half-life of 20. 5 days.
The Berkeley team reported that the isotope < sup > 257 </ sup > Lr was detected in this manner, and that it decayed by emitting an 8. 6 MeV alpha particle with a half-life of about eight seconds.
The team produced < sup > 256 </ sup > Md ( half-life of 87 minutes ) when they bombarded an < sup > 253 </ sup > Es target with alpha particles ( helium nuclei ) in the Berkeley Radiation Laboratory's 60-inch cyclotron (< sup > 256 </ sup > Md was the first isotope of any element to be synthesized one atom at a time ).
This isotope has a relatively short half-life ( 21 hours ) and so its use was limited by shipping times.
Nickel-78's half-life was recently measured to be 110 milliseconds and is believed to be an important isotope involved in supernova nucleosynthesis of elements heavier than iron.
Chemical separation of the new formed elements from the uranium yielded material with low half-life, and, therefore, Fermi announced the discovery of a new element in 1934, though this was soon found to be mistaken.
Ultimately, Joe Chip learns that Runciter, in fact, was the sole survivor of the explosion on the moon, and that his messages to the group are the result of his attempts to communicate with them while they are in half-life.
Protactinium was first identified in 1913 by Kasimir Fajans and Oswald Helmuth Göhring and named brevium because of the short half-life of the specific isotope studied, namely protactinium-234.
Although a half-life was not accurately determined, later calculations indicated that the product was most likely rutherfordium-259 ( abbreviated as < sup > 259 </ sup > Rf in standard notation ):
This gave strong evidence for the formation of RfCl < sub > 4 </ sub >, and although a half-life was not accurately measured, later evidence suggested that the product was most likely < sup > 259 </ sup > Rf.
According to the BMDO, the research on neutral particle beam accelerators, which was originally funded by the SDIO, could eventually be used to reduce the half-life of nuclear waste products using accelerator-driven transmutation technology.
A half-life of 0. 89 ms was calculated: decays into by alpha decay.
In a quantum-tunneling model, the alpha decay half-life of < sup > 294 </ sup > Uuo was predicted to be 0. 66 ms with the experimental Q-value published in 2004.
Detection was by spontaneous fission of the claimed parent isotope with half-life of 5 minutes.
Gamow solved a model potential for the nucleus and derived from first principles a relationship between the half-life of the alpha-decay event process and the energy of the emission, which had been previously discovered empirically, and was known as the Geiger-Nuttall law.
A single atom of flerovium, decaying by 9. 67 MeV alpha-emission with a half-life of 30 s, was produced and assigned to < sup > 289 </ sup > Fl.
This time two atoms of flerovium were produced, decaying by 10. 29 MeV alpha-emission with a half-life of 5. 5 s. They were assigned as < sup > 287 </ sup > Fl .< ref name =" 99Og02 "> Once again, this activity has not been seen again and it is unclear what nucleus was produced.

half-life and initially
Some elements, such as iodine-131, have a short half-life ( around 8 days in this case ) and thus they will cease to be a problem much more quickly than other, longer-lived, decay products, but their activity is therefore much greater initially.

half-life and determined
The team determined a half-life of 2. 1 seconds, in contrast to earlier reports of 47 ms and suggested that the two half-lives might be due to different isomeric states of < sup > 262 </ sup > Rf.
While tritium has several different experimentally determined values of its half-life, the National Institute of Standards and Technology lists 4, 500 ± 8 days ( approximately 12. 32 years ).
Its half-life is constant, and therefore its level is mainly determined by the rate of production ( and hence the severity of the precipitating cause ).
Its half-life has been determined to be approximately 170 years ( 0. 21 MeV ), and it decays by beta emission to < sup > 32 </ sup > P ( which has a 14. 28 day half-life ) and then to < sup > 32 </ sup > S.

half-life and at
The longest half-life is the neutron deficient < sup > 77 </ sup > Br at 2. 376 days.
The longest half-life on the neutron rich side is < sup > 82 </ sup > Br at 1. 471 days.
Ninety – four different chemical elements or types of atoms based on the number of protons are observed on earth naturally, having at least one isotope that is stable or has a very long half-life.
Californium-252, with a half-life of about 2. 64 years, is the most common isotope used and is produced at the Oak Ridge National Laboratory in the United States and the Research Institute of Atomic Reactors in Russia.
Iodine-131, which also emits beta particles that are far more damaging to tissues at short range, has a half-life of approximately 8 days.
Because < sup > 60 </ sup > Fe has such a long half-life, its persistence in materials in the solar system at high enough concentrations may have generated observable variations in the isotopic composition of < sup > 60 </ sup > Ni.
Following initial work between 1958 – 1964, in 1966, a team at the Flerov Laboratory of Nuclear Reactions ( FLNR ) reported that they had been able to detect < sup > 250 </ sup > Fm from the decay of a parent nucleus (< sup > 254 </ sup > No ) with a half-life of ~ 50s, in contradiction to the Berkeley claim.
This decay process is at a much slower rate than the initial de-excitation and is dependent on unique half-life of the radioactive nucleus.
The half-life of fluorine-18 is long enough that radiotracers labeled with fluorine-18 can be manufactured commercially at offsite locations and shipped to imaging centers.
Recent experiments at the Super-Kamiokande water Cherenkov radiation detector in Japan gave lower limits for proton half-life, at 90 % confidence level, of years via antimuon decay and years via positron decay.
The first study produced evidence for a spontaneous fission with a 0. 3 second half-life and another one at 8 seconds.
In 1970, team also studied the same reaction with oxygen-18 and identified < sup > 261 </ sup > Rf with a half-life of 65 seconds ( later refined to 75 seconds ).< ref name = 70Gh01 > Later experiments at the Lawrence Berkeley National Laboratory in California also revealed the formation of a short-lived isomer of < sup > 262 </ sup > Rf ( which undergoes spontaneous fission with a half-life of 47 ms ), and spontaneous fission activities with long lifetimes tentatively assigned to < sup > 263 </ sup > Rf.
While the moment in time at which a particular nucleus decays is unpredictable, a collection of atoms of a radioactive nuclide decays exponentially at a rate described by a parameter known as the half-life, usually given in units of years when discussing dating techniques.
Accurate radiometric dating generally requires that the parent has a long enough half-life that it will be present in significant amounts at the time of measurement ( except as described below under " Dating with short-lived extinct radionuclides "), the half-life of the parent is accurately known, and enough of the daughter product is produced to be accurately measured and distinguished from the initial amount of the daughter present in the material.
Generally a shorter half-life leads to a higher time resolution at the expense of timescale.
They are all radioactive, with a half-life much shorter than the age of the Earth, so any atoms of these elements, if they ever were present at the Earth's formation, have long since decayed.
This isotope has such a long half-life, at, that its radioactivity can be ignored.

0.582 seconds.