Evidence for a Core-excited Isomeric 31/2^-State in²⁰⁹Po

Abstract

Using alpha particles from the Stockholm 225-cm cyclotron, gamma rays from the 208Pb(α, 3n) reaction have been studied. Excitation functions, angular distributions, prompt and delayed gamma rays and gamma-gamma coincidences were measured. The results give strong evidence for a 31/2- isomeric state in 209 84Po125 with a half-life of 118 ± 3 ns, which is interpreted as being mainly due to the core-excited πh 9/2πi 13/2νg 9/2 (ν-2)0+ configuration.

On the yrast two proton-two neutron hole states in208Po

“…This gives a value of c~ k = 0.10_+ 0.03 which suggests M 1 multipolarity. -The multipolarity of the 603.1 keV transition remains unknown because there is a transition of the same energy in 2~ [1][2][3][4][5][6][7] which is also populated (for details compare the yy-coincidence spectra in Figure 7). -The angular distribution of the 856.3 keV ?-ray has negative Az, suggesting a stretched dipole transition.…”

“…Interconfigurational transition in this yrast plot is thus represented by vertical lines. In cases where both neutron holes and protons simultaneously change their configurations, the transition can only occur by admixtures and these transitions should thus be delayed and may have measurable half-lives using the isomer recoil conversion electron method [7]. A few additional remarks should be made on the lower and higher part of the level scheme.…”

In-beam studies of203, 205Bi and shell-model features of odd-a bismuth isotopes

“…Excitation energies, decay modes and half-lives have been explained on the basis of this model, the calculations being done using single-particle orbitals and two-nucleon interactions [1]. However, when the number of valence nucleons N grows, the calculation procedure becomes very tedious and for N > 4 the pairwise type of calculation, as elaborated in Ref.…”

“…However, when the number of valence nucleons N grows, the calculation procedure becomes very tedious and for N > 4 the pairwise type of calculation, as elaborated in Ref. 1, must be abandoned. Another method has been introduced recently [-2, 3], in which an N-particle wave function IN) is expressed in the form [N)…”

Evidence for a 3.6 minute isomeric 12? state of the ?h 11 2/?1 vi 13 2/?1 configuration in206Tl and effective two-particle interactions

“…8 two-particle cases: 2~ [1], 2~ 2~ 2~ 21~ 21~ 21~ [2], and 2~ 12 three-particle cases: 2~ [3] , 2~ 2~ 2~ 2~ 2~ 211pb, mBi, 211Po, 211At [4], 2~ [5], and 2~ [6] and 16 four-particle cases: 2~ [7], 2~ 2~ 2~ 2Ogpt, 2~ ' 2~ ' 21~ ' 212pb ' 2tZBi ' 212p0 ' 212At ' 212Rn, 21~ [8], 2~ [9], 2~…”