First online multireflection time-of-flight mass measurements of isobar chains produced by fusion-evaporation reactions: Toward identification of superheavy elements via mass spectroscopy.

Using a multireflection time-of-flight mass spectrograph located after a gas cell coupled with the gas-filled recoil ion separator GARIS-II, the masses of several a-decaying heavy nuclei were directly and precisely measured. The nuclei were produced via fusion-evaporation reactions and separated from projectilelike and targetlike particles using GARIS-II before being stopped in a helium-filled gas cell. Time-of-flight spectra for three isobar chains, 204Fr-204Rn-204At-204Po, 205Fr-205Rn-205At-205Po-205Bi, and 206Fr-206Rn-206At, were observed. Precision atomic mass values were determined for 204-206Fr, 204,205Rn, and 204,205At. Identifications of 205Bi, 204,205Po, 206Rn, and 206At were made with N≲10 detected ions, representing the next step toward use of mass spectrometry to identify exceedingly low-yield species such as superheavy elemention [ABSTRACT FROM AUTHOR]