Coulomb blocking of sequential tunnel ionization in complex systems

When atoms and molecules are exposed to intense low frequency laser fields, the dominant response is sequential tunnel ionization of charge states with increasing ionization potential. Sequential ionization is assumed to proceed as separate one electron processes. The theoretical analysis developed here reveals that in complex systems sequential tunnel ionization can be inhibited by Coulomb blocking. When ionization potentials of subsequent charge states are close to each other, multiple tunneling events can occur during a half cycle and in close proximity, so that a tunneled electron can block the next tunneling electron. In sub-nm clusters driven by near infrared single-cycle pulses, Coulomb blocking reduces two-electron sequential tunneling by up to 2-3 orders of magnitude.Peer Reviewe