Enhanced ionization of counterrotating electrons via doorway states in ultrashort circularly polarized laser pulses.

Atto- or femtosecond laser pulses potentially provide the opportunity to generate ultrashort spin-polarized electron pulses for probing chiral systems and magnetic properties of materials on ultrafast timescales. A key element in the generation of spin-polarized electrons is a selectivity in ionization to the sense of the electron's rotation in the initial state with respect to the rotation direction of the laser field. Based on numerical solutions of the time-dependent Schrodinger equation we predict a surprisingly large enhancement in the emission of electrons, that are initially counterrotating with respect to the rotation of the applied field, during the interaction of rare gas atoms with ultrashort circular polarized laser pulses in the intermediate few-photon ionization regime. The physical mechanism behind this observation is related to resonant enhanced ionization via states close in energy to the initial states.