Attosecond electron–spin dynamics in Xe 4d photoionization

Abstract

The photoionization of xenon atoms in the 70–100 eV range reveals several fascinating physical phenomena such as a giant resonance induced by the dynamic rearrangement of the electron cloud after photon absorption, an anomalous branching ratio between intermediate Xe+ states separated by the spin-orbit interaction and multiple Auger decay processes. These phenomena have been studied in the past, using in particular synchrotron radiation, but without access to real-time dynamics. Here, we study the dynamics of Xe 4d photoionization on its natural time scale combining attosecond interferometry and coincidence spectroscopy. A time-frequency analysis of the involved transitions allows us to identify two interfering ionization mechanisms: the broad giant dipole resonance with a fast decay time less than 50 as, and a narrow resonance at threshold induced by spin-flip transitions, with much longer decay times of several hundred as. Our results provide insight into the complex electron-spin dynamics of photo-induced phenomena.

Relativistic Two-photon Matrix Elements for Attosecond Delays

“…While RRPA theory was originally developed in the late seventies by Johnson and Cheng to describe one-photon ionization cross sections in heavy elements [69,70], the interest in such phenomena is revived by recent RABBIT experiments that have targeted heavy elements. Firstly, Jordan et al [71] and Jain et al [72] have compared photoelectrons from the fine-structure split valance orbitals: 4p j and 5p j with j = 1/2 and 3/2 of Krypton and Xenon atoms, respectively, and secondly, Jain et al [73] and Zhong et al [74], have compared photoelectrons from inner orbitals in Xenon, down to the 4d orbital. The 4d orbital is of special interest since it is known to posses a giant collective resonance in the photoionization cross section, as evidenced by MBPT in the early seventies by Amusia and Wendin [75,76].…”

“…Our goal here is to treat the whole process within a relativistic framework and below we discuss the different points where the relativistic treatment differs from that of the non-relativistic one with an effective ionic potential for IR exchange [41][42][43]. We also mention that the method presented here has already been utilized in various projects, such as [49,74], without any detailed description of the theoretical formulation. A full development of the Two-Photon Two-Color Relativistic Random Phase Approximation (2P2C-RRPA) is beyond the scope of the present work, but we expect that it would not lead to any major modification of the results presented here, because we base all our theory in the length gauge formulation of the light-matter interaction, where the one-body ionic potential description of IR exchange processes is a good approximation [44].…”

Probing electronic decoherence with high-resolution attosecond photoelectron interferometry

“…The absorption of an attosecond light pulse by matter leads to the emission of a photoelectron wavepacket (EWP) corresponding to the coherent superposition of continuum states. The measurement of the amplitude and phase of the EWPs, using attosecond streaking [1] or the reconstruction of attosecond beating by interference of two-photon transitions (RABBIT) technique [2] provides information on the photoionization dynamics in atoms and molecules in the gas phase [3][4][5][6][7][8][9][10] as well as in solids [11,12] and liquids [13]. One of the successful applications of the RABBIT technique has been the study of the ionization dynamics close to an autoionization resonance [14][15][16][17][18][19].…”

Three-electron correlations in strong laser field ionization: Spin induced effects

“…For an additional resolution of ionization delays, the coincidence scheme was assisted by a streaking technique [27,31,32]. An alternative path for accessing realtime dynamics implies a combination of coincidence spec-troscopy with an attosecond interferometry [33,34].…”

“…Importantly, recent coincidence experimental schemes [33][34][35][36][37][38] are kinematically complete, that is, momenta, position and detection time are measured for each charged particle explicitly. With increased energy resolution [33,34] one is able to catch fine interference structures that form the quantum fingerprint of the laser-driven electron dynamics. Those recent advances removed the limitations on the number of particles detected: there is no need need to use ionic momenta for recalculating electronic ones.…”