Evidence for a {bf T}-shape break-up pattern in the triple photoionization of Li

We examine the angular distributions of all three electrons ionized from Li by a single photon near the triple ionization threshold using a fully quantum-mechanical treatment. We find strong evidence for a {\bf T}-shape break-up pattern at 5 eV excess energy as previously predicted by quasi-classical simulations [A. Emmanouilidou and J. M. Rost, \jpb {\bf 39}, 4037 (2006); A. Emmanouilidou, P. Wang, and J. M. Rost, \prl {\bf 100}, 063002 (2008)]. This finding is in conflict with the expected Wannier break-up dynamics of three electrons moving at mutual angles of 120$^{\circ}$, which is expected to hold at energies a few eV above threshold. We use our quantum-mechanical approach to explore the physical mechanisms behind this unusual break-up configuration.