Effect of electron correlations on attosecond photoionization delays in the vicinity of the Cooper minima of argon

Abstract

Attosecond photoionization delays have mostly been interpreted within the single-particle approximation of multi-electron systems. The strong electron correlation between the photoionization channels associated with the 3p and 3s orbitals of argon presents an interesting arena where this single-particle approximation breaks down. Around photon energies of 42 eV, the 3s photoionization channel of argon experiences a "Cooper-like" minimum, which is exclusively the result of inter-electronic correlations with the 3p shell. Photoionization delays around this "Cooper-like" minimum have been predicted theoretically, but experimental verification has remained a challenge since the associated photoionization cross section is inherently very low. Here, we report the measurement of photoionization delays around the Cooper-like minimum that were acquired with the 100 kHz High-Repetition 1 laser system at the ELI-ALPS facility. We report relative photoionization delays reaching up to unprecedented values of 430±20 as, as a result of electron correlation. Our experimental results are in partial agreement with state-of-the-art theoretical results, but also demonstrate the need for additional theoretical developments.

Attosecond photoionization dynamics in the vicinity of the Cooper minima in argon

“…In conclusion, we have demonstrated the potential of the Rainbow RABBIT method to separate the contributions of the 3s and 3p ionization channels in argon and to measure the corresponding atomic delays for a wide range of energies (34-68 eV) that includes both 3s and 3p Cooper minima. The extracted 3s − 3p delay differences are in good agreement with earlier results in the 34-40 eV range [12], being, however, at variance with recent measurements [49]. Our results are in excellent agreement with the predictions of many-body perturbation theory in a 24 eV range around the 3p Cooper minimum, revealing the high accuracy of both experiment and theory in this region.…”

Generation and characterization of few-pulse attosecond pulse trains at 100kHz repetition rate

“…A number of groups have reported the generation of high-order harmonics at high repetition rate [9,10,11,12]. So far, with the exception of [13,14], who reported RABBITT experiments at 100 kHz using a fiber laser post-compressed to 40 fs, no pump-probe experiments or pulse characterization have been reported. In particular, there have not been any reports yet demonstrating the complete characterization of attosecond pulses generated using a high repetition rate, OPCPA driver, which is important given concerns that have existed in the past about spatio-temporal couplings in such systems [15,16,9].…”

High power, high repetition rate laser-based sources for attosecond science

“…It is worth mentioning that a fiber-based CPA in combination with nonlinear compression in HCFs has been presented as the method of choice at the extreme light infrastracture (ELI) facility for providing CEP-stable, few-cycle pulses with high average power and high repetition rate for experiments in attosecond science [76,77]. Recently, one of these systems at ELI, featuring one compression stage, was utilized to generate APTs and perform pump-probe experiments [78][79][80].…”

“…In fact, in some of these experiments, CEP-dependent XUV emission has been observed [180,186], showing the possibility of generating IAPs. Some of these high repetition rate XUV sources have been implemented for different applications such as time-and angle-resolved photoemission spectroscopy in solids [187], coherent diffractive imaging [188], or attosecond pump-probe spectroscopy [79]. In particular, high repetition rate OPCPAs and post-compressed Yb-CPAs are being implemented in attosecond pump-probe experiments with coincidence detection of ions and photoelectrons [189][190][191][192][193].…”