Competition between allowed and first-forbidden decays of At and expansion of the Po level scheme
Brunet, M.*; Podolyk, Zs.*; Berry, T. A.*; Brown, B. A.*; Carroll, R. J.*; Lica, R.*; Sotty, Ch.*; Andreyev, A. N.; Borge, M. J. G.*; Cubiss, J. G.*; Fraile, L. M.*; Fynbo, H. O. U.*; Gamba, E.*; Greenlees, P.*; Harkness-Brennan, L. J.*; Huyse, M.*; Judson, D. S.*; Konki, J.*; Kurcewicz, J.*; Lazarus, I.*; Madurga, M.*; Marginean, N.*; Marginean, R.*; Marroquin, I.*; Mihai, C.*; Ncher, E.*; Negret, A.*; Pascu, S.*; Page, R. D.*; Perea, A.*; Phrompao, J.*; Piersa, M.*; Pucknell, V.*; Rahkila, P.*; Rapisarda, E.*; Regan, P. H.*; Rotaru, F.*; Rudigier, M.*; Shand, C. M.*; Shearman, R.*; Simpson, E. C.*; Stora, T.*; Tengblad, O.*; Van Duppen, P.*; Vedia, V.*; Vinals, S.*; Wadsworth, R.*; Warr, N.*; De Witte, H.*
The structure of Po populated through the EC/ decay of At is investigated using -ray spectroscopy at the ISOLDE Decay Station. The presented level scheme contains 27 new excited states and 43 new transitions, as well as a further 50 previously observed rays which have been (re)assigned a position. Through the analysis using the shell model calculations approximately half of the -decay strength of At is found to proceed via allowed decay and half via first-forbidden decay. The first-forbidden transitions predominantly populate core excited states at high excitation energies, which is qualitatively understood using shell model considerations.