Revisiting the tunnelling site of electrons in strong field enhanced   ionization of molecules
  We investigated electron emissions in strong field enhanced ionization of asymmetric diatomic molecules by quantum calculations. It is demonstrated that the widely-used intuitive physical pic- ture, i.e., electron wave packet direct ionization from the up-field site (DIU), is incomplete. Besides DIU, we find another two new ionization channels, the field-induced excitation with subsequent ionization from the down-field site (ESID), and the up-field site (ESIU). The contributions from these channels depend on the molecular asymmetry and internuclear distance. Our work provides a more comprehensive physical picture for the long-standing issue about enhanced ionization of diatomic molecules. 
Cheng Huang, Pengfei Lan, Yueming Zhou, Qingbin Zhang, Kunlong Liu,   and Peixiang Lu
physics.atom-ph