Response to "Discovery of the element with atomic number 112" by Robert C. Barber, Heinz W. Gaggeler, Paul J. Karol, Hiromichi Nakahara, Emanuele Vardaci and Erich Vogt (PAC-REP-08-03-05)

Abstract

Based on two alpha-particle chains the Joint Working Party (JWP) Report assigns the priority for discovering element 112 to work done in 1996 and 2002 at GSI, Darmstadt. By doing this it ignores the data presented to the JWP about the discovery of this element already back in 1971 by Marinov et al. In those measurements about one hundred fission fragments were observed from two Hg sources separated from two W targets irradiated with 24 GeV protons. Furthermore, the masses of the fissioning species were measured and interpreted as being due to the atom and four different molecules of element 112 with atomic mass number 272-273. By ignoring these data the JWP disregards the facts that mass measurement is considered by the Transfermium Working Group (TWG) report as an "excellent criterion" and that "chemical methods can yield excellent assignment criteria". It is shown below that all the arguments given by the JWP attempting to justify their decision are refutable. In particular, their refusal to accept the possibility of the existence of long-lived isomeric states as a consistent interpretation of the data is unjustified, since, among other observations, evidence has been found recently for the existence of such states in naturally-occurring neutron deficient 211,213,217,218Th isotopes, and in the superheavy element region, at atomic mass numbers A = 261 and A = 265 (most probably 261Rg and 265Rg), and at A = 292, Z =~122 (eka-Th), with half-lives t1/2 >= 10^8 y.