Sub-cycle Oscillations in Virtual States Brought to Light

Chini, Michael; Wang, Xiaowei; Yan, Chao; Wu, Yi; Zhao, Dongfeng; Telnov, Dmitry A.; Chu, Shih‐I; Chang, Zenghu

doi:10.1038/srep01105

Cited by 168 publications

(206 citation statements)

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“…In general, these features can be attributed to a process wherein the broadband VUV pulse induces a time-dependent dipole response in the molecular target, which is perturbed by the NIR field. The mechanism of the laser perturbation can be further classified by scrutinizing the absorption dynamics within a particular excited-state absorption line: resonant processes involving coupling of neighboring states through the absorption or emission of one NIR photon typically result in relatively slowly varying spectral features such as absorption line splitting (analogous to Autler-Townes splitting [39]) and perturbed free induction decay [40], whereas nonresonant couplings involving two or more NIR photons result in fast oscillations with periodicity shorter than the dressing laser optical cycle [4]. These features reveal information about the field-free evolution of the electronic wave packet in the interval between the two pulses [2,41,42].…”

Section: Discussionmentioning

confidence: 99%

“…The delay was scanned using a mirror mounted on a piezoelectric stage and was actively stabilized to an error of ∼25 asec RMS during the experiments. Details of the experimental setup can be found in previous publications [4,29] and references therein.…”

Section: A Experimental Setupmentioning

confidence: 99%

“…With the availability of high-resolution VUV spectrometers [15], one can conceivably monitor the recurrence of the vibronic wave packet created close to a localized reaction center, even in solution. ATAS has already been applied successfully to selected studies of strongfield ionization [5] and dissociation [16], wave-packet motion [3,4,6,17,18], and correlated electron dynamics [19][20][21][22], as well as phase transition dynamics in condensed matter [23,24], with unprecedented energy and time resolution. As ATAS encodes both the amplitudes and phases of interacting states, reconstruction and control of an electron wave packet-in both space and time-has been achieved [22].…”

Section: Introductionmentioning

confidence: 99%

“…In the absence of external degrees of freedom, electronic wave packets excited in atoms by an isolated attosecond pulse [2][3][4] or by strong-field ionization [5,6] exhibit a high degree of coherence [7] and can be probed via the photoelectron or transient absorption spectrum. In molecules [8][9][10], electronic excitation is accompanied by redistribution of charge and the subsequent rearrangement-rotation, torsion, bond elongation-of the nuclei, on a time scale of femtoseconds to picoseconds, which can ultimately lead to the breaking of chemical bonds.…”

Section: Introductionmentioning

confidence: 99%

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Reconstruction of an excited-state molecular wave packet with attosecond transient absorption spectroscopy

et al. 2016

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Attosecond science promises to allow new forms of quantum control in which a broadband isolated attosecond pulse excites a molecular wave packet consisting of a coherent superposition of multiple excited electronic states. This electronic excitation triggers nuclear motion on the molecular manifold of potential energy surfaces and can result in permanent rearrangement of the constituent atoms. Here, we demonstrate attosecond transient absorption spectroscopy (ATAS) as a viable probe of the electronic and nuclear dynamics initiated in excited states of a neutral molecule by a broadband vacuum ultraviolet pulse. Owing to the high spectral and temporal resolution of ATAS, we are able to reconstruct the time evolution of a vibrational wave packet within the excited B 1 u + electronic state of H 2 via the laser-perturbed transient absorption spectrum.

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Section: Discussionmentioning

confidence: 99%

Section: A Experimental Setupmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Reconstruction of an excited-state molecular wave packet with attosecond transient absorption spectroscopy

et al. 2016

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“…Dressed by the femtosecond laser field, the nearly free electron will be subject to a ponderomotive shift of its energy during the pulse. Such kind of transient energy shift was observed as a shift of the ionization threshold in helium [19]. Instead of studying the energy displacement, we focus on the transient phase shift that occurs while the atom is dressed, and which gives rise to a modified line shape.…”

Section: Fig 1 Dipole Control Model (A)mentioning

confidence: 99%

In situ characterization of few-cycle laser pulses in transient absorption spectroscopy

Blättermann¹,

Ott²,

Kaldun³

et al. 2015

Opt. Lett.

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Fig. 1. Dipole control model. (a)Perturbations to the field-free evolution of the dipole response (dashed blue) are treated as instantaneous modifications of the amplitude and phase expressed by the complex factor A. The perturbed decay (dark purple, light purple) is shown for two time-delays ( 1 , 2 ) leading to very different spectral line shapes (inset). (b) Treatment of a ponderomotive shift in the dipole control model. Instead of a continuously modified dipole phase ( ) , the effect of the dressing field is approximated by a single phase step at time , the peak of the intense laser pulse envelope. Since the temporal profile of the dressing laser pulse intensity is mapped onto ( ) via Eq. (4), it is possible to determine both the pulse duration and intensity.In situ characterization of few-cycle laser pulses in transient absorption spectroscopy Attosecond transient absorption spectroscopy has thus far been lacking the capability to simultaneously characterize the intense laser pulses at work within a time-resolved quantum-dynamics experiment. However, precise knowledge of these pulses is key to extracting quantitative information in strong-field highly nonlinear light-matter interactions. Here, we introduce and experimentally demonstrate an ultrafast metrology tool based on the time-delay-dependent phase shift imprinted on a strong-field driven resonance. Since we analyze the signature of the laser pulse interacting with the absorbing spectroscopy target, the laser pulse duration and intensity are determined in situ. As we also show, this approach allows for the quantification of time-dependent bound-state dynamics in one and the same experiment. In the future, such experimental data will facilitate more precise tests of strong-field dynamics theories.In the transformative field of ultrafast light-matter interaction, characterization of strong-field laser pulses is crucial in order to draw quantitative conclusions from measurement results. Based on the detection of photoelectrons, the attosecond streaking technique provides insight into the system's underlying quantum dynamics on the natural electronic time scale, combined with a powerful characterization of the used strong-field laser pulses [1][2][3]. Being capable of resolving bound-state quantum dynamics, the all-optical method of attosecond transient absorption spectroscopy (ATAS) [4][5][6][7][8][9][10][11][12] is an important complement to photoelectron-based methods. In addition to being sensitive to bound-bound transitions, ATAS allows targets to be studied all the way from a natural -weak-field -environment up to the strong-field regime. Using attosecond pulsed extreme-ultraviolet (XUV) light together with (typically) femtosecond nearinfrared (NIR) pulses in a pump-probe scheme, dynamical processes leave their fingerprints in the spectrum of the transmitted XUV light. Yet unlike streaking, up to now ATAS lacks the possibility for in-situ characterization of the femtosecond NIR laser pulse, which drives and controls the underlying electron dynamics. ...

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Sub‐cycle Dynamics of High Harmonic Generation of Ne Atoms Excited by Attosecond Pulses and Driven by Near‐infrared Laser Fields: A Self‐Interaction‐Free TDDFT Approach

Chou

2015

J Chinese Chemical Soc

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In the framework of the self‐interaction‐free time‐dependent density‐functional theory (TDDFT), we have performed three‐dimensional ab initio calculations of Ne atoms in near‐infrared (NIR) laser fields subject to excitation by a single extreme ultraviolet (XUV) attosecond pulse (SAP). The TDDFT equations are solved accurately and efficiently by means of the time‐dependent generalized pseudo spectral (TDGPS) method. We have explored the transient dynamical behavior of the sub‐cycle high harmonic generation (HHG) for transitions from the excited states to the ground state and found oscillation structures with respect to the time delay between the SAP and NIR fields. We investigate the harmonic emission spectrum from singly excited state 2p3s, 2p4s, 2p3d, 2p5s, 2p4d and 2p6s, 2p5d and the virtual states 2p3p‐, 2p4f‐ and 2p4p+ as the function of time delay. We explore the sub‐cycle Stark shift phenomenon in NIR fields and its influence on the photon emission process. Our analysis reveals several novel features of the sub‐cycle transient HHG dynamics and spectra, the quantum interference pattern between different multiphoton excitation pathways, and we identify the mechanisms responsible for the observed peak splitting in the photon emission spectra.

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Sub-cycle Oscillations in Virtual States Brought to Light

Cited by 168 publications

References 23 publications

Reconstruction of an excited-state molecular wave packet with attosecond transient absorption spectroscopy

Reconstruction of an excited-state molecular wave packet with attosecond transient absorption spectroscopy

In situ characterization of few-cycle laser pulses in transient absorption spectroscopy

Sub‐cycle Dynamics of High Harmonic Generation of Ne Atoms Excited by Attosecond Pulses and Driven by Near‐infrared Laser Fields: A Self‐Interaction‐Free TDDFT Approach

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