Isotopes of ununpentium

From Wikipedia, the free encyclopedia
Jump to: navigation, search

Ununpentium (Uup) is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 288Uup in 2004. There are four known radioisotopes from 287Uup to 290Uup.

Table[edit]

nuclide
symbol
Z(p) N(n)  
isotopic mass (u)
 
half-life decay mode(s) daughter
isotope(s)
nuclear
spin
287Uup 115 172 287.19070(52)# 32(+155-14) ms α 283Uut
288Uup 115 173 288.19274(62)# 87(+105-30) ms α 284Uut
289Uup[n 1] 115 174 289.19363(89)# 220 ms[1] α 285Uut
290Uup[n 2] 115 175 290.19598(73)# 16 ms[1] α 286Uut
  1. ^ Not directly synthesized, created as decay product of 293Uus
  2. ^ Not directly synthesized, created as decay product of 294Uus

Notes[edit]

  • Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
  • Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC which use expanded uncertainties.

Nucleosynthesis[edit]

Chronology of isotope discovery
Isotope Year discovered Discovery reaction
287Uup 2003 243Am(48Ca,4n)
288Uup 2003 243Am(48Ca,3n)
289Uup 2009 249Bk(48Ca,4n)[1]
290Uup 2009 249Bk(48Ca,3n)[1]

Target-projectile combinations[edit]

The table below contains various combinations of targets and projectiles which could be used to form compound nuclei with Z=115. Each entry is acombination for which calculations have provided estimates for cross section yields from various neutron evaporation channels. The channel with the highest expected yield is given.

Target Projectile CN Attempt result
208Pb 75As 283Uup Reaction yet to be attempted
232Th 55Mn 287Uup Reaction yet to be attempted
238U 51V 289Uup Failure to date
237Np 50Ti 287Uup Reaction yet to be attempted
244Pu 45Sc 289Uup Reaction yet to be attempted
243Am 48Ca 291Uup[2][3] Successful reaction
241Am 48Ca 289Uup Planned Reaction
248Cm 41K 289Uup Reaction yet to be attempted
249Bk 40Ar 289Uup Reaction yet to be attempted
249Cf 37Cl 286Uup Reaction yet to be attempted

Hot fusion[edit]

Hot fusion reactions are processes that create compound nuclei at high excitation energy (~40–50 MeV, hence "hot"), leading to a reduced probability of survival from fission. The excited nucleus then decays to the ground state via the emission of 3–5 neutrons. Fusion reactions utilizing 48Ca nuclei usually produce compound nuclei with intermediate excitation energies (~30–35 MeV) and are sometimes referred to as "warm" fusion reactions. This leads, in part, to relatively high yields from these reactions.

238U(51V,xn)289−xUup[edit]

There are strong indications that this reaction was performed in late 2004 as part of a uranium(IV) fluoride target test at the GSI. No reports have been published suggesting that no products atoms were detected, as anticipated by the team.[4]

243Am(48Ca,xn)291−xUup (x=2,3,4)[edit]

This reaction was first performed by the team in Dubna in July–August 2003. In two separate runs they were able to detect 3 atoms of 288Uup and a single atom of 287Uup. The reaction was studied further in June 2004 in an attempt to isolate the descendant 268Db from the 288Uup decay chain. After chemical separation of a +4/+5 fraction, 15 SF decays were measured with a lifetime consistent with 268Db. In order to prove that the decays were from dubnium-268, the team repeated the reaction in August 2005 and separated the +4 and +5 fractions and further separated the +5 fractions into tantalum-like and niobium-like ones. Five SF activities were observed, all occurring in the +5 fractions and none in the tantalum-like fractions, proving that the product was indeed isotopes of dubnium.

In a series of experiments between October 2010 – February 2011, scientists at the FLNR studied this reaction at a range of excitation energies. They were able to detect 21 atoms of 288115 and one atom of 289115, from the 2n exit channel. This latter result was used to support the synthesis of ununseptium. The 3n excitation function was completed with a maximum at ~8 pb. The data was consistent with that found in the first experiments in 2003.

Reaction yields[edit]

The table below provides cross-sections and excitation energies for hot fusion reactions producing ununpentium isotopes directly. Data in bold represent maxima derived from excitation function measurements. + represents an observed exit channel.

Projectile Target CN 2n 3n 4n 5n
48Ca 243Am 291Uup 3.7 pb, 39.0 MeV 0.9 pb, 44.4 MeV

Theoretical calculations[edit]

Decay characteristics[edit]

Theoretical calculations using a quantum-tunneling model support the experimental alpha-decay half-lives.[5]

Evaporation residue cross sections[edit]

The table below contains various target-projectile combinations for which calculations have provided estimates for cross section yields from various neutron evaporation channels. The channel with the highest expected yield is given.

MD = multi-dimensional; DNS = Di-nuclear system; σ = cross section

Target Projectile CN Channel (product) σmax Model Ref
243Am 48Ca 291Uup 3n (288Uup) 3 pb MD [2]
243Am 48Ca 291Uup 4n (287Uup) 2 pb MD [2]
243Am 48Ca 291Uup 3n (288Uup) 1 pb DNS [3]
242Am 48Ca 290Uup 3n (287Uup) 2.5 pb DNS [3]

References[edit]

  1. ^ a b c d Oganessian, Y. T.; Abdullin, F. S.; Bailey, P. D. et al. (2010). "Synthesis of a New Element with Atomic Number Z=117". Physical Review Letters 104 (14): 142502. Bibcode:2010PhRvL.104n2502O. doi:10.1103/PhysRevLett.104.142502. PMID 20481935.  edit
  2. ^ a b c Zagrebaev, V (2004). "Fusion-fission dynamics of super-heavy element formation and decay". Nuclear Physics A 734: 164. Bibcode:2004NuPhA.734..164Z. doi:10.1016/j.nuclphysa.2004.01.025. 
  3. ^ a b c Feng, Z; Jin, G; Li, J; Scheid, W (2009). "Production of heavy and superheavy nuclei in massive fusion reactions". Nuclear Physics A 816: 33. arXiv:0803.1117. Bibcode:2009NuPhA.816...33F. doi:10.1016/j.nuclphysa.2008.11.003. 
  4. ^ "List of experiments 2000–2006". Univerzita Komenského v Bratislave. 
  5. ^ C. Samanta, P. Roy Chowdhury and D.N. Basu (2007). "Predictions of alpha decay half lives of heavy and superheavy elements". Nucl. Phys. A 789: 142–154. arXiv:nucl-th/0703086. Bibcode:2007NuPhA.789..142S. doi:10.1016/j.nuclphysa.2007.04.001. 


Isotopes of flerovium Isotopes of ununpentium Isotopes of livermorium
Table of nuclides