Alpha-decay-correlated mass measurement of 206,207Ra using an {\alpha}-TOF detector equipped MRTOF-MS system

The atomic masses of the isotopes 206,207Ra have been measured via decay-correlated mass spectroscopy using a multi-reflection time-of-flight mass spectrograph equipped with an {\alpha}-TOF detector. The Ra isotopes were produced as fusion-evaporation products in the 51V+159Tb reaction system and delivered by the gas-filled recoil ion separator GARIS-II at RIKEN. The {\alpha}-TOF detector provides for high-accuracy mass measurements by correlating time-of-flight signals with subsequent {\alpha}-decay events. The masses of 207gRa and 207mRa were directly measured using a multi-reflection time-of-flight mass spectrograph equipped with an {\alpha}-TOF detector. A mass excess of ME = 3538(15) keV/c2 and an excitation energy of Eex = 552(42) keV were determined. The {\alpha}-decay branching ratio of 207mRa, b{\alpha} = 0.26(20), was directly determined from decay-correlated time-of- flight signals, and the reduced alpha width of 207mRa was calculated to be {\delta}2 = 50+62-41 keV from the branching ratio. The spin-parity of 207mRa was confirmed to be J{\pi} = 13/2 from decay correlated mass measurement results.