J. M. Kenneally

Indication for a volatile element 114

Abstract Recently, the chemical investigation of element 112 revealed a highly volatile, noble metallic behaviour, as expected for the last group 12 member of the periodic table. The observed volatility and chemical inertness were ascribed to the growing influence of relativistic effects on the chemical properties of the heaviest elements with increasing nuclear charge. Here, we report for the first time on gas phase chemical experiments aiming at a determination of element 114 properties. This element was investigated using its isotopes 287114 and 288114 produced in the nuclear fusion reactions of 48Ca with 242Pu and 244Pu, respectively. Identification of three atoms of element 114 in thermochromatography experiments and their deposition pattern on a gold surface indicates that this element is at least as volatile as simultaneously investigated elements Hg, At, and element 112. This behaviour is rather unexpected for a typical metal of group 14.

Synthesis of Superheavy Nuclei in 48Ca-Induced Reactions

neutron-rich isotopes 242,244 Pu, 243 Am, 245,248 Cm and 249 Cf with 48 Ca projectiles. The decay properties of the synthesized nuclei are consistent with the consecutive α-decays originating in the decays of parent nuclides 286,287,288,289 114, 287,288 115, 290,291,293 116 and 294 118 produced in the 2n- to 5n-evaporation channels. The present observations can be considered to be experimental evidence of the existence of the “island of stability” of superheavy elements.

Random probability analysis of recent 48Ca experiments

Abstract.A Monte Carlo random probability analysis developed at LLNL for heavy element research was performed for recent experiments aimed at the synthesis of nuclides with Z≥112 and N≥170, to estimate the probability that observed decay chains were a result of a random event. Low probabilities ( < 10-4% for most decay chains) were found.

Synthesis, Decay Properties, and Identification of Superheavy Nuclei Produced in 48Ca‐induced Reactions

Thirty‐four new nuclides with Zu2009=u2009104–116, 118 and Nu2009=u2009161–177 have been synthesized in the complete‐fusion reactions of 238U, 237Np, 242,244Pu, 243Am, 245,248Cm, and 249Cf targets with 48Ca beams. The masses of evaporation residues were identified through measurements of the excitation functions of the xn‐evaporation channels and from cross bombardments. The decay properties of the new nuclei agree with those of previously known heavy nuclei and with predictions from different theoretical models. A discussion of self‐consistent interpretations of all observed decay chains originating from the parent isotopes 282,283112, 282113, 286–289114, 287,288115, 290–293116, and 294118 is presented. Decay energies and lifetimes of the neutron‐rich superheavy nuclei as well as their production cross sections indicate a considerable increase in the stability of nuclei with the approach to the theoretically predicted nuclear shells with Nu2009=u2009184 and Zu2009=u2009114.