High-spin states in206Bi populated in the205Tl(?, 3n) reaction

Abstract

Using alpha-particles in the energy range 35-51MeV and in-beam gamma ray and conversion electron spectroscopy techniques the reaction 2~ 3n)Z~ was studied. A 15 _+1 ns isomeric 15 + state was found at an excitation energy of 3147keV in 2~ The main configuration of the isomeric state is suggested to be 7"ch9/2 vp~/~i~/2. The isomeric state decays mainly through a stretched cascade of five gamma rays to the previously known 0.88ms 10-state of the 7ch9/2 vi13~2(j-2)o + configuration at an excitation energy of 1045 keV. A shell model calculation of the yrast states has been performed and it is found that the calculation agrees fairly well with the experiments. The average deviation between experimental and calculated energies for the yrast states with angular momenta in the region 6-18 is +4keV and the root mean square deviation is 22keV.

Yrast structure of206Bi: Isomeric states and one-proton-particle, three-neutron-hole excitations

“…These high-lying states in 206 Bi could not be reached in previous studies such as with the 205 Tl(α,3nγ) reaction of Ref. [1].…”

“…The 206 Bi ground state, with spin-parity J π =6 + , is of πh 9/2 νf −1 5/2 character, with the isomeric (T 1/2 =7.7 µs) J π =4 + member of the πh 9/2 νp −1 1/2 multiplet lying only 60 keV above it. At higher excitation energies, two other isomeric states have been identified in an earlier study with the 205 Tl(α,3nγ) reaction [1]. These are the 10 − state at 1045 keV with T 1/2 =0.89 ms and an assigned (πh 9/2 νi −1 13/2 )×ν −2 0 configuration, and the 15 + excita- * Present address: Department of Physics, University of York, Heslington, York YO10 5DD, UK † Present address: National Nuclear Data Center, Brookhaven National Laboratory, Upton, New York 11973-5000, USA tion of πh 9/2 νp −1 1/2 i −2 13/2 character located at 3147 keV, with a 15.6-ns half-life.…”

“…(2) (5) 0 0 a γ rays seen also in Ref. [1] b intensity too weak to be determined It was noticed by double gating on the 553-, 480-, 361-, and 713-keV lines in the prompt-delayed-delayed cube that the 937-keV transition is clearly visible and must be preceding in time this cascade. This observation pointed to the existence of yet another isomeric state at 9233 keV decaying via the 713-keV line.…”

“…The 206 Bi decay scheme established in previous studies [1] is printed in black and white in Fig. 1.…”

“…These are the 10 − state at 1045 keV with T 1/2 =0.89 ms and an assigned (πh 9/2 νi −1 13/2 )×ν −2 0 configuration, and the 15 + excita- * Present address: Department of Physics, University of York, Heslington, York YO10 5DD, UK † Present address: National Nuclear Data Center, Brookhaven National Laboratory, Upton, New York 11973-5000, USA tion of πh 9/2 νp −1 1/2 i −2 13/2 character located at 3147 keV, with a 15.6-ns half-life. The highest 206 Bi yrast states known thus far; i.e., the 17 + and 18 + levels at 3604 and 4305 keV, have been located in the 205 Tl(α,3nγ) work as well [1].…”