$\alpha$-decay of the new isotope $^{187}$Po: Probing prolate structures beyond the neutron mid-shell at N = 104
Résumé
The new neutron-deficient isotope 187Po has been identified in the complete fusion reaction 46Ti+144Sm-->187Po+3n at the velocity filter SHIP. Striking features of the 187Po alpha decay are the strongly-hindered decay to the spherical ground state and unhindered decay to a surprisingly low-lying deformed excited state at 286 keV in the daughter nucleus 183Pb. Based on the potential energy surface calculations, the 187Po ground state and the 286 keV excited state in 183Pb were interpreted as being of prolate origin. The systematic deviation of the alpha-decay properties in the lightest odd-A Po isotopes relative to the smooth behavior in the even-A neighbors is discussed. Improved data for the decay of 187Bim,g were also obtained.