Decay of mass-separated Tl190 and Hg190

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Radioactive sources containing Tl190 and Hg190 have been produced and mass separated with the University Isotope Separator on line to the Oak Ridge isochronous cyclotron. Multiscaled spectra of γ rays, x rays, conversion electrons, and positrons were obtained, and γ-γ and γ-x-ray coincidences were measured. Two isomers in Tl190 decay have half-lives of 2.6 ± 0.3 min (2-) and 3.7 ± 0.3 min (7+). From β decay endpoint energies the 7+ and 2- isomers lie within 0.1 MeV of each other, but which is the ground state was not determined. Both isomers have ground-state QEC values of approximately 7 MeV. The 2- level undergoes β decay primarily to the 2+ states at 416.4 and 1099.9 keV in Hg190, while the decay of the 7+ isomer feeds a number of different states with spins ranging from 5 to 9. We observed the 5-, 7-, and 9- members of the previously identified structure of negative-parity states resulting from coupling of a rotation-aligned i132 neutron with 3p32 and 2f52 neutrons. Some additional states having decays consistent with (6-) and (8-) assignments perhaps are candidates for less aligned members of the 13/2+ band coupled with p32 and f52 neutrons. The 20-min Hg190 isotope decays approximately 65% of the time to a level at 171.5 keV, thus making it difficult to study other levels in Au190. Four new states in Au190 were definitely established, while several new ones were suggested by the present work. The populated levels are predominantly low spin and are fairly closely spaced. The logft value for the transition to the 171.5 keV level is 5.7, so it is likely that this state has a spin and parity of 1+. RADIOACTIVITY Tl190, Tlm190, Hg190 [from Ta, W(O16,xp+yn), E=143,124 MeV]; mass-separated radioactivities. Measured T12, Eγ, Iγ, Ice, Eβ, γγ coin, γx coin. Deduced logft, Q. Hg190, Au190 deduced levels, J, π, ICC, Λ. © 1976 The American Physical Society.

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Physical Review C

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