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Monday, June 10, 2019
3:00 PM - 4:00 PM
CNLS Conference Room (TA-3, Bldg 1690)

Colloquium

CANCELLED-Attosecond two-photon interferometric measurements of resonant photoemission delays

CANCELLED-Luca Argenti

CANCELLED--Autoionizing states are a pervasive aspect of atomic and molecular ionization and a distinct signature of electronic correlation. Only with the advent of attosecond sources, however, did it become possible to resolve the evolution of autoionizing states in real time, and to study how they are affected, and can be controlled, by light [1-4]. Ab initio studies are key to interpret many current attosecond pump-probe experiments [5-8]. Time-dependent close coupling (TDCC), on the one side, and finite-pulse perturbative methods, on the other side, have affirmed themselves as the leading tools to describe the ionization of atoms under the influence of ultrashort pulses, beyond the single-active-electron approximation [9-13]. In this seminar I will illustrate through examples the decay dynamics of autoionizing states from model systems to rare-gas atoms in realistic conditions. Among the techniques covered, I will discuss a recent XUV-pump IR-probe photoionization protocol that employs pairs of counter-rotating consecutive harmonics and angularly resolved photoelectron detection, thereby providing direct measurement of ionization phases. The method, which we call circular holographic ionization-phase meter (CHIP), gives also access to the phase of photoemission amplitudes of even-parity continuum states from a single time-delay measurement, since the relative phase of one- and two-photon ionization pathways is imprinted in the photoemission anisotropy [14]. These studies shed light on the concerted motion of electrons in transiently bound states, as well as on the elusive delay with which photoelectrons eventually part from their confined companions.

[1] Ott C et al., Nature 516, 374 (2014). [2] Gruson V et al., Science 354, 734 (2016). [3] Kotur M et al., Nature Commun. 7, 10566 (2016). [4] Chew A et al., Phys. Rev. A 97, 031407(R) (2018). [5] Argenti L et al., Phys. Rev. Lett 105, 053002 (2010). [6] Argenti L et al., Phys. Rev. A 87, 053405 (2013). [7] Carette T et al., Phys. Rev. A 87, 023420 (2013). [8] Cirelli C et al., Nature Commun. 9, 955 (2018). [9] Argenti L et al., Phys. Rev. A 91, 061403 (2015).[10] Jiménez Galán A et al., Phys. Rev. Lett. 113, 263001 (2014).[11] Jiménez Galán A et al., Phys. Rev. A 93, 023429 (2016).[12] Argenti L et al., Phys. Rev. A 95, 043426 (2017).[13] Ghomashi B et al., Phys. Rev. A in press (2019).[14] Donsa S et al., arXiv:1904:04380v1 [physics.atom-ph] (2019).

Host: Alexis Chacon