Lunds universitet

Denna sida på svenska This page in English

Element 115 - Proven Existence

The history of discoveries of element 115 - or Ununpentium - is summarized at

In short, first reports on the isotopes 287-115 and 288-115 have been put forward by the so-called Dubna-Livermore collaboration already in 2004. In total 4 correlated alpha-decay chains following the reaction calcium (Z=20) on americium (Z=95) were observed and attributed to element 115. These findings were later-on confirmed and extended with the isotopes 289-115 and 290-115, the latter solely as daughter of 294-117. See the link above for more details. A total of 37 decay chains starting from 287-115 (2), 288-115 (31), and 289-115 (4) are published by Yu.T. Oganessian and his collaboration.

Nevertheless, the JWG of IUPAC and IUPAP has not yet approved discovery of element 115. In particular they request an (independent and) possibly direct measure of the proton number of one of odd-proton-number elements (see the IUPAC report at doi:10.1351/PAC-REP-10-05-01, ).

This is where our experiment comes into play.

Now - whether or not the IUPAC-IUPAP JWG committee is going to approve element 115 based on previous reports and our new findings remains to be seen. They either may say "yes", or in turn ask for a statistically significant proof along the lines of our X-ray fingerprinting attempt. Our experiment demonstrates that finally, a method to perform the direct measurement of the atomic number is feasible, even for those new superheavy elements produced at rates of single atoms per day.