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Abstract In recent years laser driven attosecond sources based on loose geometry high order harmonic generation reach focused intensities as high as to induce multiphoton multiple ionization or even strong -field effects in the extreme ultraviolet spectral range. In this chapter, we review four such sources developed through collaborative efforts between FORTH, ELI-ALPS and the University of Lund together with recent results obtained in the above mentioned topics utilizing these sources. [ABSTRACT FROM AUTHOR]

The implementation of attosecond photoelectron–photoion coincidence spectroscopy for the investigation of atomic and molecular dynamics calls for a high-repetition-rate driving source combined with experimental setups characterized by excellent stability for data acquisition over time intervals ranging from a few hours up to a few days. This requirement is crucial for the investigation of processes characterized by low cross sections and for the characterization of fully differential photoelectron(s) and photoion(s) angular and energy distributions. We demonstrate that the implementation of industrial-grade lasers, combined with a careful design of the delay line implemented in the pump–probe setup, allows one to reach ultrastable experimental conditions leading to an error in the estimation of the time delays of only 12 as over an acquisition time of 6.5 h. This result opens up new possibilities for the investigation of attosecond dynamics in simple quantum systems. [ABSTRACT FROM AUTHOR]

The long-standing scientific quest of real-time tracing electronic motion and dynamics in all states of matter has been remarkably benefited by the development of intense laser-based pulsed sources with a temporal resolution in the attosecond [1 attosecond = 10−18 s] time scale. Nowadays, attosecond pulses are routinely produced in laboratories by the synthesis of the frequency components of broadband coherent extreme ultraviolet (XUV) radiation generated by the interaction of matter with intense femtosecond (fs) pulses. Attosecond pulse metrology aims at the accurate and complete determination of the temporal and phase characteristics of attosecond pulses and is one of the most innovative challenges in the broad field of ultrashort pulse metrology. For more than two decades since coherent high-brilliance broadband XUV sources have become available, fascinating advances in attosecond pulse metrology have led to the development of remarkable techniques for pulse duration measurements as well as the complete reconstruction of those pulses. Nonetheless, new challenges born from diverse fields call upon for additional efforts and continuously innovative ideas in the field. In this perspective article, we follow the history of ultrashort pulse technology tracing attosecond pulse production and characterization approaches, focus on the operation principles of the most commonly used techniques in the region where they interact with matter, address their limitations, and discuss future prospects as well as endeavors of the field to encounter contemporary scientific progress. [ABSTRACT FROM AUTHOR]

We present combined theoretical and experimental work investigating the angle-resolved phases of the photoionization process driven by a two-color field consisting of an attosecond pulse train and an infrared pulse in an ensemble of randomly oriented molecules. We derive a general form for the two-color photoelectron (and time-delay) angular distribution valid also in the case of chiral molecules and when relative polarizations of the photons contributing to the attosecond photoelectron interferometer differ. We show a comparison between the experimental data and theoretical predictions in an ensemble of methane and deuteromethane molecules, discussing the effect of nuclear dynamics on the photoionization phases. Finally, we demonstrate that the oscillating component and the phase of the two-color signal can be fitted by using complex asymmetry parameters, in perfect analogy to the atomic case.

In extreme ultraviolet spectroscopy, the photoionization process occurring in a molecule due to the absorption of a single photon can trigger an ultrafast nuclear motion in the cation. Taking advantage of attosecond photoelectron interferometry, where the absorption of the extreme ultraviolet photon is accompanied by the exchange of an additional infrared quantum of light, one can investigate the influence of nuclear dynamics by monitoring the characteristics of the photoelectron spectra generated by the two-color field. Here, we show that attosecond photoelectron interferometry is sensitive to the nuclear response by measuring the two-color photoionization spectra in a mixture of methane (CH 4 ) and deuteromethane (CD 4 ). The effect of the different nuclear evolution in the two isotopologues manifests itself in the modification of the amplitude and contrast of the oscillations of the photoelectron peaks. Our work indicates that nuclear dynamics can affect the coherence properties of the electronic wave packet emitted by photoionization on a time scale as short as a few femtoseconds.