Attosecond transient absorption spectroscopy in ionic systems

We investigated ionized wavepackets in Xenon and Krypton using attosecond transient absorption spectroscopy. The ionized system was prepared using a strong near-infrared pump pulse, while a time-delayed extreme ultraviolet attosecond pulse train acted as the probe in a non-collinear geometry. The hole wavepacket evolves with time and this is monitored using 11th or 13th high harmonics which serve to excite the system further to high-lying ionic states. The polarization and intensity of near-infrared pulse were varied, and quantum beating of the hole wave packet is monitored in the process. This approach also allows us to probe the evolution of neutral autoionizing states that exist between two spin-orbit split ionization thresholds, to gain insight into the strong-field induced decay dynamics and modification of the ionic population. These results open the door to study ionized atomic and molecular systems, as well as plasmas using the attosecond transient absorption techniques.