The burgeoning periodic table will see four more isotopes being added to its fag end.
H. M. Devaraja from the Manipal Centre of Natural Sciences at Manipal University, Karnataka — who was a part of an international collaboration — has, in a paper published in the journal Physics Letters B, claimed to have discovered four new atomic nuclei. These are one isotope each of the heavy elements berkelium (Bk, atomic number 97) and neptunium (Np, 93) and two isotopes of the element americium (Am, 95).
The researchers observed the deep inelastic multinucleon transfer reactions of Calcium 48, and Curium 248. The multinucleon reactions occur in collision of two complex nuclei. The resulting reaction sees intense dissipation of energy as well as mass distributions of the products of which neutron rich and neutron deficient products are of interest to physicists. Current techniques make it difficult to produce isotopes greater than atomic number 92.
A beam of Ca48 was projected on to a 300-nanometer-thick foil of Cu248 at GSI Helmholtzzentrum für Schwerionenforschung, Germany’s linear accelerator UNILAC (Universal Linear Accelerator — which can accelerate ions up to 60,000 kmps — or 20 per cent the speed of light). The collision threw up over 100 residual nuclei with proton numbers between 82 and 100. Of these particles, four new neutron-deficient isotopes were found, and were confirmed by studying their decay chains: 216U (the previous lowest neutron deficient isotope of Uranium discovered was 217U) that decayed within 5.5 milli seconds (ms) to Thorium; 223Am which decayed within 7.5 ms to Protactinium; 233Bk which decayed in 30s to the new-isotope 229Am, which further decayed into Neptunium.
The decay chain of the fifth isotope 219Np could not be observed as researchers believe it decayed faster than their system, whose smallest measure is 5 micro-seconds (0.000005 seconds). The known Periodic Table currently comprises over 3,000 isotopes of 114 chemical elements; while another 4,000 undiscovered isotopes are theoretically believed to exist. These isotopes, however, have far eluded experimental physicists.
“By using this method (deep inelastic multinucleon transfer), we have succeeded in generating many different atomic nuclei at once. This becomes important for the study of super-heavy elements. New isotopes, in particular those of super-heavy elements, which contain an especially large number of neutrons, cannot be made by any other method,” says author Sophia Heinz .
These experiments will form the base for further observations. The collaboration is seeing the development of the next generation separator “SuperSHIP” (which can record decay reactions of up to 100 nano seconds – that is, 0.01 micro seconds), which will enable detection of far more isotopes.
Published - September 19, 2015 04:53 pm IST
