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Abstract:
The dipole response of an excited quantum system gives direct insight into the electron
dynamics triggered by the incoming light. Spectroscopy techniques such as (attosecond)
transient absorption spectroscopy make use of the fact that the dipole response leaves
its characteristic fingerprint on the transmitted light. In this work, a general and comprehensive
model is introduced, which allows for an analytic description of dipole dynamics
triggered and modified by two ultrashort light pulses in both time and frequency
domains. Based on this description, a two-dimensional spectral representation of time
delay–resolved absorption data is developed. The power of the method to separate different
pathways of light–matter interaction, which allows for their individual investigation,
is demonstrated experimentally by studying electronic wave packet dynamics in doubly
excited helium and inner-valence excited xenon.
Furthermore, an in situ technique for characterization of the intense dressing laser pulse
that drives (nonlinear) quantum dynamics in time-resolved absorption experiments is derived
from the same analytic model and demonstrated experimentally. The possibility to
characterize these ultrashort strong-field laser pulses directly within the spectroscopy target
enhances the scope of transient absorption spectroscopy as it allows for the precise
measurement and control of electron dynamics and increases the comparability between
experiment and theory.
