Amplitude and Phase Reconstruction of Electron Wave Packets for Probing Ultrafast Photoionization Dynamics

Kim, Kyung Taec; Ko, Dong Hyuk; Park, Juyun; Choi, Nark Nyul; Kim, Chul Min; Ishikawa, Kenichi L.; Lee, Jongmin; Nam, Chang Hee

doi:10.1103/physrevlett.108.093001

Cited by 26 publications

(13 citation statements)

References 25 publications

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“…The slopes of the tilted fringes on both resonances change along t 0 , which are controlled by the phase differences between 2s2p and 2s 2 and between 2s2p and 2p 2 , respectively, in the duration after the EUV excitation and before the VIS kicks in. This feature of tilted fringes has been explained by several attosecond ionization studies [32][33][34].…”

Section: Euv-plus-vis Spectroscopysupporting

confidence: 62%

Probing dipole-forbidden autoionizing states by isolated attosecond pulses

2014

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We propose a general technique to retrieve the information of dipole-forbidden resonances in the autoionizing region. In the simulation, a helium atom is pumped by an isolated attosecond pulse in the extreme ultraviolet (EUV) combined with a few-femtosecond laser pulse. The excited wave packet consists of the S-1, P-1, and D-1 states, including the background continua, near the 2s2p(P-1) doubly excited state. The resultant electron spectra with various laser intensities and time delays between the EUV and laser pulses are obtained by a multilevel model and an ab initio time-dependent Schrodinger equation calculation. By taking the ab initio calculation as a "virtual measurement," the dipole-forbidden resonances are characterized by the multilevel model. We found that in contrast to the common assumption, the nonresonant coupling between the continua plays a significant role in the time-delayed electron spectra, which shows the correlation effect between photoelectrons before they leave the core. This technique takes the advantages of ultrashort pulses uniquely and would be a timely test for the current attosecond technology

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Section: Euv-plus-vis Spectroscopysupporting

confidence: 62%

Probing dipole-forbidden autoionizing states by isolated attosecond pulses

2014

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“…Due to the well-defined spectral coherence (i.e. phase locking 23 ) present in a highharmonic spectrum, the observation of a well-defined phase evolution υ(t) is possible 24 even in the absence of carrier-envelope-phase stabilization and without knowing the number of attosecond pulses in our few-cycle generated attosecond-pulse train (Methods -Effects of the Attosecond Pules Configuration and the Carrier Envelope Phase‖; Extended Data Figs. [4][5][6].…”

mentioning

confidence: 99%

Reconstruction and control of a time-dependent two-electron wave packet

Ott

Kaldun

Argenti

et al. 2014

Nature

278

218

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Esta es la versión de autor del artículo publicado en: This is an author produced version of a paper published in: The concerted motion of two or more bound electrons governs atomic 1 and molecular 2,3 non-equilibrium processes and chemical reactions. It is thus a long-standing scientific dream to measure and control the dynamics of two bound and correlated electrons in the quantum regime. At least two active electrons and a nucleus are required to address such quantum three-body problem 4 for which analytical solutions do not exist, a condition that is met in the helium atom. While attosecond dynamics were previously observed for singleactive electron/hole cases 5-7 , such time-resolved observation of two-electron motion thus far remained an unaccomplished challenge. Here, we measure a 1.2-femtosecond quantum beat among low-lying doubly-excited states in helium and use it to reconstruct a correlated two-electron wave packet. Our experimental method combines attosecond transientabsorption spectroscopy 5,7-9 at unprecedented high spectral resolution (20 meV s.d. near 60 eV) with an intensity-tuneable visible laser field to couple 10-12 the quantum states from the weak-field to the strong-coupling regime. Employing the Fano resonance as a phasesensitive quantum interferometer 13 , we demonstrate the coherent control of two correlated electrons, which form the basis of most covalent molecular bonds in nature. As we show, such multi-dimensional spectroscopy experiments provide benchmark data for testing fundamental few-body quantum-dynamics theory. They also light a route for site-specific measurement and control of metastable electronic transition states that are at the heart of fundamental reactions in chemistry and biology.Electrons are bound to atoms and molecules by the Coulomb force of the nuclei. Moving between atoms, they form the basis of the molecular bond. The same Coulomb force, however, acts repulsively between the electrons. This electron-electron interaction represents a major challenge in the understanding and modelling of atomic and molecular states, their structure and in particular their dynamics 2,3,14 . Here, we focus on the 1 P sp 2,n+ series 15 of doubly-excited states in helium below the N = 2 ionization threshold. They are excited by a single-photon transition from the 1 S 1s 2 ground state by the promotion of both electrons to at least principal quantum number n = 2. The states autoionize due to electron-electron interaction and their spectroscopic signature manifests as asymmetric non-Lorentzian line shapes. The latter were first observed in the 1930s 16 and attributed 17 , by Ugo Fano, to the quantum interference of bound states with the continuum to which they are coupled (Fig. 1c,d). The coupling is described by the configuration interaction V CI with the single-ionization continuum |1s,p, where one electron is in the 1s ground state and the other one is in the continuum with kinetic energy . The magnitude of V CI determines the lifetimes of the transiently bound states. In our case,...

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“…Highorder harmonic generation (HHG) from atoms driven by a strong femtosecond laser field has been investigated for the development of ultrashort coherent extreme ultraviolet (XUV) sources for attosecond physics [2,3], microscopic…”

Section: Introductionmentioning

confidence: 99%

Enhanced two-color high-harmonic generation achieved by adding an extra gas medium

et al. 2015

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imaging [4], interferometry [5], and also for the exploration of atomic and molecular structures [6,7]. This novel XUV source, however, has a significant drawback of low conversion efficiency, and various schemes have been developed to improve it. The employment of a loose focusing geometry to a long gas cell was successful in boosting the harmonic yield to a μJ level in the 40-nm region by increasing the interaction cross section and length [8,9]. Spatial modification to a specific profile, such as flat-top shape, was also successful in expanding the effective harmonic generation volume [10,11]. Methods using waveguide structures have been investigated in order to improve phase matching between a driving laser pulse and generated harmonics [12,13]. These efforts made it possible to apply high-harmonic light source to specific applications such as XUV spectroscopy and microscopy, while it should be enhanced further to improve the applicability.Another approach developed to significantly enhance harmonic efficiency is the use of a synthesized laser field. As a simple synthesized field, a two-color laser field, consisting of a fundamental laser field and its second harmonic (SH), was applied to HHG [14,15]. It significantly improved the harmonic efficiency by generating short-path harmonics from atoms under a strongly ionizing condition, as compared to single-color harmonics generated under a weak ionization condition. We applied the strong harmonic by a two-color laser field to soft X-ray imaging experiments [4], and we found that the intensity of harmonic source should be improved further to enhance the spatial resolution of single-shot microscopy. More recently, twogas schemes were proposed to enhance the harmonic efficiency using a mixed gas medium or two gas cells [16,17]. In order to enhance the harmonic intensity further, the twogas media approach can be employed in two-color HHG scheme. AbstractThe high-harmonic generation in a two-color laser field, consisting of a 30-fs Ti:Sapphire laser pulse and its second harmonic, could be enhanced by installing an extra gas medium of Ar in front of the harmonic generation medium of He. The effects of the extra medium were examined by analyzing harmonic spectra taken under different experimental conditions. The observed characteristics of enhanced harmonic generation were explained in terms of the profile modification of the two-color laser beam. The 34th harmonic at 23.5 nm and 38th harmonic at 21.5 nm were enhanced 2.5 and 2 times, respectively.

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Amplitude and Phase Reconstruction of Electron Wave Packets for Probing Ultrafast Photoionization Dynamics

Cited by 26 publications

References 25 publications

Probing dipole-forbidden autoionizing states by isolated attosecond pulses

Probing dipole-forbidden autoionizing states by isolated attosecond pulses

Reconstruction and control of a time-dependent two-electron wave packet

Enhanced two-color high-harmonic generation achieved by adding an extra gas medium

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