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Isotopes of seaborgium
Seaborgium (106Sg) is a synthetic element and so has no stable isotopes. A standard atomic weight cannot be given. The first isotope to be synthesized was 263Sg in 1974. There are fourteen known radioisotopes from 257Sg to 271Sg (except 270Sg) and five known isomers (259mSg, 261mSg, 263mSg, 265mSg, and 267mSg). The longest-lived isotopes are 269Sg with a half-life of 13 minutes and 267Sg with a half-life of 9.8 minutes. Due to a low number of measurements, and the consequent overlapping measurement uncertainties at the confidence level corresponding to one standard deviation, a definite assignment of the most stable isotope cannot be made.
This section deals with the synthesis of nuclei of seaborgium by so-called "cold" fusion reactions. These are processes that create compound nuclei at low excitation energy (~10–20 MeV, hence "cold"), leading to a higher probability of survival from fission. The excited nucleus then decays to the ground state via the emission of one or two neutrons only.
The first attempt to synthesise seaborgium in cold fusion reactions was performed in September 1974 by a Soviet team led by G. N. Flerov at the Joint Institute for Nuclear Research at Dubna. They reported producing a 0.48 s spontaneous fission (SF) activity, which they assigned to the isotope 259Sg. Based on later evidence it was suggested that the team most likely measured the decay of 260Sg and its daughter 256Rf. The TWG concluded that, at the time, the results were insufficiently convincing.
The Dubna team revisited this problem in 1983–1984 and were able to detect a 5 ms SF activity assigned directly to 260Sg.
The team at GSI studied this reaction for the first time in 1985 using the improved method of correlation of genetic parent-daughter decays. They were able to detect 261Sg (x=1) and 260Sg and measured a partial 1n neutron evaporation excitation function.
In December 2000, the reaction was studied by a team at GANIL, France; they were able to detect 10 atoms of 261Sg and 2 atoms of 260Sg to add to previous data on the reaction.
After a facility upgrade, the GSI team measured the 1n excitation function in 2003 using a metallic lead target. Of significance, in May 2003, the team successfully replaced the lead-208 target with more resistant lead(II) sulfide targets (PbS), which will allow more intense beams to be used in the future. They were able to measure the 1n,2n and 3n excitation functions and performed the first detailed alpha-gamma spectroscopy on the isotope 261Sg. They detected ~1600 atoms of the isotope and identified new alpha lines as well as measuring a more accurate half-life and new EC and SF branchings. Furthermore, they were able to detect the K X-rays from the daughter rutherfordium isotope for the first time. They were also able to provide improved data for 260Sg, including the tentative observation of an isomeric level. The study was continued in September 2005 and March 2006. The accumulated work on 261Sg was published in 2007. Work in September 2005 also aimed to begin spectroscopic studies on 260Sg.
The team at the LBNL recently restudied this reaction in an effort to look at the spectroscopy of the isotope 261Sg. They were able to detect a new isomer, 261mSg, decaying by internal conversion into the ground state. In the same experiment, they were also able to confirm a K-isomer in the daughter 257Rf, namely 257m2Rf.
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Isotopes of seaborgium AI simulator
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Isotopes of seaborgium
Seaborgium (106Sg) is a synthetic element and so has no stable isotopes. A standard atomic weight cannot be given. The first isotope to be synthesized was 263Sg in 1974. There are fourteen known radioisotopes from 257Sg to 271Sg (except 270Sg) and five known isomers (259mSg, 261mSg, 263mSg, 265mSg, and 267mSg). The longest-lived isotopes are 269Sg with a half-life of 13 minutes and 267Sg with a half-life of 9.8 minutes. Due to a low number of measurements, and the consequent overlapping measurement uncertainties at the confidence level corresponding to one standard deviation, a definite assignment of the most stable isotope cannot be made.
This section deals with the synthesis of nuclei of seaborgium by so-called "cold" fusion reactions. These are processes that create compound nuclei at low excitation energy (~10–20 MeV, hence "cold"), leading to a higher probability of survival from fission. The excited nucleus then decays to the ground state via the emission of one or two neutrons only.
The first attempt to synthesise seaborgium in cold fusion reactions was performed in September 1974 by a Soviet team led by G. N. Flerov at the Joint Institute for Nuclear Research at Dubna. They reported producing a 0.48 s spontaneous fission (SF) activity, which they assigned to the isotope 259Sg. Based on later evidence it was suggested that the team most likely measured the decay of 260Sg and its daughter 256Rf. The TWG concluded that, at the time, the results were insufficiently convincing.
The Dubna team revisited this problem in 1983–1984 and were able to detect a 5 ms SF activity assigned directly to 260Sg.
The team at GSI studied this reaction for the first time in 1985 using the improved method of correlation of genetic parent-daughter decays. They were able to detect 261Sg (x=1) and 260Sg and measured a partial 1n neutron evaporation excitation function.
In December 2000, the reaction was studied by a team at GANIL, France; they were able to detect 10 atoms of 261Sg and 2 atoms of 260Sg to add to previous data on the reaction.
After a facility upgrade, the GSI team measured the 1n excitation function in 2003 using a metallic lead target. Of significance, in May 2003, the team successfully replaced the lead-208 target with more resistant lead(II) sulfide targets (PbS), which will allow more intense beams to be used in the future. They were able to measure the 1n,2n and 3n excitation functions and performed the first detailed alpha-gamma spectroscopy on the isotope 261Sg. They detected ~1600 atoms of the isotope and identified new alpha lines as well as measuring a more accurate half-life and new EC and SF branchings. Furthermore, they were able to detect the K X-rays from the daughter rutherfordium isotope for the first time. They were also able to provide improved data for 260Sg, including the tentative observation of an isomeric level. The study was continued in September 2005 and March 2006. The accumulated work on 261Sg was published in 2007. Work in September 2005 also aimed to begin spectroscopic studies on 260Sg.
The team at the LBNL recently restudied this reaction in an effort to look at the spectroscopy of the isotope 261Sg. They were able to detect a new isomer, 261mSg, decaying by internal conversion into the ground state. In the same experiment, they were also able to confirm a K-isomer in the daughter 257Rf, namely 257m2Rf.