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 alpha-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, Fr-204-Rn-204-At-204-Po-204, Fr-205-Rn-205-At-205-Po-205-Bi-205, and Fr-206-Rn-206-At-206, were observed. Precision atomic mass values were determined for Fr204-206, Rn-204,Rn-205, and At-204,At-205. Identifications of Bi-205, Po-204,Po-205, Rn-206, and At-206 were made with N less than or similar to 10 detected ions, representing the next step toward use of mass spectrometry to identify exceedingly low-yield species such as superheavy element ions.