This thesis study theoretically the electron wave packet generated by an attosecond pulse train (APT) which is probed with a time-delayed laser pulse. The APT creates an excited state and a continuum electron wave packet. By ionizing the excited state with an IR, a delayed new continuum electron wave packet is created. The interference of the wave packets from the two paths, as reflected in angle-resolved photoelectron spectra, is analyzed analytically. Using the analytical expressions, here examine the possibility of retrieving information on the electron wave packet generated by the APT.