Adiabaticity condition for non-Hermitian Hamiltonians
  We generalize the concept of population for non-Hermitian systems in different ways and identify the one best suited to characterize adiabaticity. An approximate adiabaticity criterion consistent with this choice is also worked out. Examples are provided for different processes involving two-level atoms with decay. 
S. Ib\'a\~nez and J. G. Muga
quant-ph