α -decay-correlated mass measurement of Ra206,207g,m using an α -TOF detector equipped multireflection time-of-flight mass spectrograph system

Abstract

The atomic masses of the isotopes Ra206,207 have been measured via decay-correlated mass spectroscopy using a multireflection time-of-flight mass spectrograph equipped with an α-TOF detector. The Ra isotopes were produced as fusion-evaporation products in the V51+Tb159 reaction system and delivered by the gas-filled recoil ion separator GARIS-II at RIKEN. The α-TOF detector provides for high-accuracy mass measurements by correlating time-of-flight signals with subsequent α-decay events. The masses of Ra206 and Ra207g,m were directly measured using a multireflection time-of-flight mass spectrograph equipped with an α-TOF detector. The mass excesses of Ra206,207g and the excitation energy of Ra207m were determined to be ME=3540(50)keV/c2, 3538(15)keV/c2, and Eex=552(42) keV, respectively. The α-decay branching ratio of Ra207m, bα=0.26(20), was directly determined from decay-correlated time-of-flight signals, and the reduced α width of Ra207m was calculated to be δ2=43−34+68 keV from the branching ratio. The spin-parity of Ra207m was confirmed to be Jπ=13/2+ from decay correlated mass measurement results.1 MoreReceived 20 June 2021Accepted 28 September 2021Corrected 29 October 2021DOI:https://doi.org/10.1103/PhysRevC.104.044617©2021 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAlpha decayBinding energy & massesNuclear reactionsProperties190 ≤ A ≤ 219Nuclear Physics