Coherent evolution of electronic wavepackets determine the course of physical and chemical processes. Recently, we demonstrated a highly differentiated measurement of electronic wavepackets by using Raman interferences and delayed detection, which is a major improvement over the conventional photoelectron interferometry method used by us and others. This new approach allows us to concurrently access high resolution in both temporal and spectral domains. We employed it to characterize the evolution of an autoionizing wavepacket launched between the two spin-orbit split ionization thresholds of Argon. As shown in the figure below, an XUV+NIR pump excites autoionizing states. Raman probe redistributes the amplitudes causing beats. Autoionization provides high resolution compared to photoionization. Differential spectrogram in middle column showing photoelectron channel (top), Raman interferometry in autoionization (middle) and its theory (bottom).  Last column shows FFT’s where there is lack of energy resolution in direct photoelectrons (top), but we have exquisite identification of beats (middle) and theory (bottom) in the autoionization channel. 

Attosecond XUV pulses coherently prepares the atomic or molecular polarizations, and a time-delay femtosecond IR or visible pulse is used to perturb the polarization. This allows us to observe interesting dynamic phenomena such as AC Stark shifts, light-induced virtual states, spectral lineshape manipulation, quantum-path interference, resonant pulse propagation, etc. We have applied ATA to study complex dynamics in optically thick helium target and in oxygen molecule. Experimental investigations are then compared with the TDSE simulations and Multiconfiguration Time-dependent Hartree-Fock (MCTDHF) calculations.