Beyond the Single-Atom Response in Absorption Line Shapes: Probing a Dense, Laser-Dressed Helium Gas with Attosecond Pulse Trains

Liao, Chen‐Ting; Sandhu, Arvinder; Camp, Seth; Schafer, Kenneth J.; Gaarde, Mette B.

doi:10.1103/physrevlett.114.143002

Cited by 36 publications

(40 citation statements)

References 26 publications

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“…Indeed, it is known that direct photoabsorption measurements do not yield accurate absorption cross sections for discrete transitions [34], primarily due to line saturation effects, and the calculated field-free absorption cross section is in excellent agreement with accurate measurements using electron-energy-loss spectroscopy [35]. Furthermore, recent studies have shown that temporal reshaping of the VUV pulse, which accompanies photoabsorption in dense gas targets, may distort the delay-dependent features in ATAS [36][37][38]. Both of these issues can in principle be overcome through the use of a higher-resolution VUV spectrometer, which would permit the use of lower gas pressures.…”

Section: Resultsmentioning

confidence: 51%

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: Resultsmentioning

confidence: 51%

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

et al. 2016

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“…Recent ATAS experiments focus on properties and evolution of XUV initiated dipole polarization in atoms by using a delayed NIR pulse as a perturbation. In this scenario, many interesting time-dependent phenomena have been observed, including AC Stark shifts [21], light-induced states [22], quantum beats or quantum path interferences [23], strong-field line shape control [24], and resonant-pulse-propagation induced XUV pulse reshaping effects [25,26].…”

Section: Introductionmentioning

confidence: 99%

Probing autoionizing states of molecular oxygen with XUV transient absorption: Electronic-symmetry-dependent line shapes and laser-induced modifications

Liao

Haxton

et al. 2017

Phys. Rev. A

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We used extreme ultraviolet (XUV) transient absorption spectroscopy to study the autoionizing Rydberg states of oxygen in electronically and vibrationally resolved fashion. XUV pulse initiates molecular polarization and near infrared (NIR) pulse perturbs its evolution. Transient absorption spectra show positive optical density (OD) change in the case of nsσ g and ndπ g autoionizing states of oxygen and negative OD change for ndσ g states. Multiconfiguration time-dependent HartreeFock (MCTDHF) calculations are used to simulate the transient absorption and the resulting spectra and temporal evolution agree with experimental observations. We model the effect of nearinfrared (NIR) perturbation on molecular polarization and find that the laser induced phase shift model agrees with the experimental and MCTDHF results, while the laser induced attenuation model does not. We relate the electronic state symmetry dependent sign of the OD change to the Fano parameters of the static absorption line shapes.

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“…One appealing solution to this problem is to increase the pressure-length product of the absorbing medium. However, recent works have demonstrated that this caused modifications of the absorption lineshapes due to resonant effects in the XUV pulse propagation, which complicates the interpretation [16].In this letter, we overcome the limitations of TRAX experiments by measuring Transient Reshaping of the Emission spectrum of the XUV light (T-REX). We excite a bound electronic wavepacket in argon atoms by arXiv:1701.06352v2 [physics.atom-ph]…”

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confidence: 99%

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Phase-resolved two-dimensional spectroscopy of electronic wave packets by laser-induced XUV free induction decay

et al. 2017

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We present a novel time-and phase-resolved, background-free scheme to study the extreme ultraviolet dipole emission of a bound electronic wavepacket, without the use of any extreme ultraviolet exciting pulse. Using multiphoton transitions, we populate a superposition of quantum states which coherently emit extreme ultraviolet radiation through free induction decay. This emission is probed and controlled, both in amplitude and phase, by a time-delayed infrared femtosecond pulse. We directly measure the laser-induced dephasing of the emission by using a simple heterodyne detection scheme based on two-source interferometry. This technique provides rich information about the interplay between the laser field and the Coulombic potential on the excited electron dynamics. Its background-free nature enables us to use a large range of gas pressures and to reveal the influence of collisions in the relaxation process.Transient Absorption Spectroscopy (TAS) in the extreme ultraviolet (XUV) range is a powerful technique for ultrafast dynamical studies, from the gas phase [1][2][3] to the solid state [4,5]. The recent progress of attosecond science has made the extension of TAS to the attosecond regime (ATAS) a reality. In the past few years, different configurations of ATAS experiments have emerged. In the first and most intuitive scheme, the XUV attosecond pulses probe a sample that has been pre-excited by an infrared (IR) pump laser pulse. This scheme was for instance used to follow the ultrafast coherent hole dynamics initiated in strong-field ionized krypton [1]. In the second arrangement, the XUV and IR pulses are temporally overlapped. The XUV absorption thus probes the IR-dressed atomic or molecular states, allowing the observation of light-induced states [6,7] as well as sub-cycle AC-Stark-shifts [8]. Finally, in what turned out to be the most widely used scheme, the XUV pulse comes first and serves as a pump, exciting a broadband superposition of quantum states through single-photon absorption. The wavepacket relaxes by coherently emitting XUV radiation (called XUV Free Induction Decay, XFID) that interferes with the incident light. A delayed IR laser field is used to follow or control the relaxation dynamics, such that these experiments can be seen as Transient Reshaping of the Absorption spectrum of the XUV light (TRAX) [9,10].In TRAX experiments, the delayed IR laser pulse has three main effects on the XFID emission ( Fig. 1) : (i) Damping of the emission by ionization of the excited states. This effect induces a lowering and a spectral broadening of the absorption features [2]. (ii) Field coupling of different electronic states, leading to population transfers. The resulting amplitude reshaping of the electronic wavepacket can be detected through temporal beatings in the absorption signal, as demonstrated in atoms [9,10] and molecules [11,12]. (iii) Phase shift induced by the Stark-shift of the excited states. This laser-induced phase was shown to enable full control over the absorption lineshapes, from Lorentz ...

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Beyond the Single-Atom Response in Absorption Line Shapes: Probing a Dense, Laser-Dressed Helium Gas with Attosecond Pulse Trains

Cited by 36 publications

References 26 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

Probing autoionizing states of molecular oxygen with XUV transient absorption: Electronic-symmetry-dependent line shapes and laser-induced modifications

Phase-resolved two-dimensional spectroscopy of electronic wave packets by laser-induced XUV free induction decay

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