The last two decades have witnessed the emergence of attosecond science, a new discipline that leverages light pulses with duration at the same characteristic time scale of electronic motion in atoms, molecules, and condensed matter. Attosecond spectroscopy has proven a particularly useful tool to monitor and control the evolution of transiently bound electronic states. These states, also known as autoionizing states, play a fundamental role in the ionization and charge transfer processes in matter. This thesis is a theoretical study on the role of such autoionizing states in the ionization of polyelectronic atoms by ultrashort pulses, which has been instrumental to four joint experimental and theoretical studies: i) with the group of Zenghu Chang, at UCF, concerning the core ionization of the argon atom at the L2,3 edge; ii) with the group of Arvinder Sandhu, at the University of Arizona, on the control of the lifetime of autionizing states in the argon atom, as well as iii) on the measurement of the lifetime of argon's dark autoionizing states via non-colinear four-wave mixing; iv) with the group of Louis DiMauro, at the Ohio State University, on the verification of the Kramers-Krönig relations in the ionization of laser-dressed argon. We have adopted several complementary theoretical approaches. In solving the time-dependent Schroedinger equation, we introduced a novel "essential states" procedure, which drastically reduces the cost of ab initio calculations. We developed a model that shows how destructive interference between autoionization and radiative ionization channels can stabilize transient states, explaining experimental observations and providing the first evidence for a phenomenon first predicted four decades ago. We have devised the formalism needed to extrapolate, from the single-atom response, the off-axis dipolar emission from an extended sample, and implemented it to theoretically reproduce, for the first time and with semi-quantitative accuracy, four-wave mixing experimental spectra in argon. Lastly, we developed a model for propagating light through a laser-dressed sample, demonstrating its use by predicting the pressure dependence of transient absorption spectra in model systems.


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Graduation Date





Argenti, Luca


Doctor of Philosophy (Ph.D.)


College of Sciences



Degree Program



CFE0009153; DP0026749





Release Date

August 2025

Length of Campus-only Access

3 years

Access Status

Doctoral Dissertation (Campus-only Access)

Restricted to the UCF community until August 2025; it will then be open access.