Complete characterization of a coherent superposition of atomic states by asymmetric attosecond photoionization

A method for the complete characterization of a coherent superposition of atomic states, prepared by a pump pulse, is presented. The technique is based on the measurement of two asymmetry parameters, related to the photoionization of the generated electron wave packet by isolated attosecond pulses. By numerically solving the fully three-dimensional time-dependent Schrödinger equation, it is demonstrated that the temporal evolution of the population of the atomic states involved in the coherent superposition can be mapped onto the amplitude-modulated asymmetry in the direction of the attosecond probe pulse polarization. The results of the numerical simulations show that it is possible to achieve a unique determination of static and time-dependent populations by measuring only a few ionization asymmetry parameters. © 2012 American Physical Society.