Bulletin of the American Physical Society
52nd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 66, Number 6
Monday–Friday, May 31–June 4 2021; Virtual; Time Zone: Central Daylight Time, USA
Session M02: Attosecond pulses and attosecond dynamicsLive
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Chair: Guillaume Laurent, Auburn University |
Wednesday, June 2, 2021 2:00PM - 2:12PM Live |
M02.00001: Theoretical study of vacuum ultraviolet pulse characterization from autocorrelation signals Spencer R Walker, Ran B Reiff, Agnieszka Jaron-Becker, Andreas Becker When an intense laser pulse interacts with a gas of atoms their valence electrons are excited and ionized. If an optical autocorrelator is used to split the pulse into two copies and superimpose them onto a target with known spectra and variable temporal delay, then information about the laser pulse is inscribed onto the ionized electrons. We present results of a theoretical study how one can infer the shape of a vacuum ultraviolet pulse from this measured total ionization yield using a perturbative approach for two-photon ionization with Gaussian pulses. |
Wednesday, June 2, 2021 2:12PM - 2:24PM Live |
M02.00002: Novel characterization method for an isolated attosecond pulse by using CEP dependence Dong Hyuk Ko, Graham G Brown, Chunmei Zhang, Paul B Corkum We demonstrate a new measurement method for characterizing an isolated attosecond pulse. Traditionally, attosecond pulses are measured by photoelectron streaking, which relies on two-photon ionization using a secondary laser pulse. Recently, in situ measurement of attosecond pulses was accomplished by perturbing high harmonic generation process with a weak laser field in the nonlinear medium. Here, we demonstrate a novel attosecond measurement method without the need of a photoelectron source or a secondary laser pulse. Instead, we utilize the strong carrier-envelope-phase (CEP) sensitivity of the attosecond pulse generation process by a few-cycle driver. Effectively, the CEP-dependent modulation on the spectrum of the attosecond pulse can be explained by the time-domain grating diffraction. When a light irradiates few grooves on a grating, the far-field diffraction pattern is extremely sensitive to the groove position. Analogously, the narrow envelope of the few-cycle driver serves as a temporal grating and the CEP implies the relative position of the grating lines. We use this to measure the attosecond pulse. Consequently, we confirm our measurement method in experiment and theoretically show its validity for the measurement of a broadband attosecond pulse. |
Wednesday, June 2, 2021 2:24PM - 2:36PM Live |
M02.00003: Temporal profile reshaping of high-intensity attosecond x-ray pulses by resonant propagation through dense gas Kai Li, Dimitris Koulentianos, Gilles Doumy, Linda Young, Mette B Gaarde, Zhaoheng Guo, James P Cryan, Agostino Marinelli With ten orders of magnitude higher peak brightness than synchrotron radiation, XFELs offer opportunities to exploring x-ray nonlinear physics. Resonant propagation of ultra-intense attosecond x-ray pulses through dense gases creates nonlinear phenomena such as self-induced transparency and stimulated Raman scattering [1]. The strong interaction also induces temporal reshaping of the pulse. We present simulations of resonant propagation of isolated high-intensity attosecond pulses from the Linac Coherent Light Source [2]. The attosecond pulses develop femtosecond oscillating tails (Burnham-Chiao ringing) and attosecond beats emerging from stimulated Raman scattering during propagation. We propose to measure these features by photoelectron streaking with circularly polarized light [2]. Attosecond pulse reshaping could be used for future FEL experiments or could be an issue when propagating pulses through resonant media. |
Wednesday, June 2, 2021 2:36PM - 2:48PM Live |
M02.00004: Towards the complete phase profiling of attosecond wave packets Nicolas Douguet, Jaco Fuchs, Stefan Donsa, Fernando Martin, Joachim Burgdorfer, Luca Argenti, Laura Cattaneo, Ursula Keller
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Wednesday, June 2, 2021 2:48PM - 3:00PM Live |
M02.00005: Resolving an electronic wavepacket composed of dark autoionizing neutral states in Argon Alexander C Plunkett, James Wood, Miguel Alarcon, Chris H Greene, Arvinder S Sandhu We study the dynamics of autoionizing Rydberg states in Argon using time-resolved photoelectron spectroscopy and demonstrate a novel technique of energy- and time-resolving electron wavepackets in atoms and molecules. An autoionizing $(3p)^{-1}nf^\prime$ wavepacket is excited using a two-color pulse and is probed by an ionizing time-delayed IR pulse. The differential changes in the electron yield due to the action of the IR pulse are energy and angle analyzed using a velocity map imaging spectrometer. In addition to measuring quantum beats in the photoelectron signal, we also observe strong quantum beating in the autoionization channel modulated by a two IR photon process. The latter channel is analyzed energetically with few-meV resolution while retaining femtosecond time-resolution, which is in contrast to traditional photoelectron measurements where it is not possible to obtain both high energy and time-resolution. The experimental results show good agreement with time-dependent perturbation theory calculations. |
Wednesday, June 2, 2021 3:00PM - 3:12PM Live |
M02.00006: Optical Measurement of Multielectron During Recollision Graham G Brown, Dong Hyuk Ko, Chunmei Zhang, Paul B Corkum The study of photoionization time delays is one of the major achievements of attosecond science. These measurements are typically performed using photoelectron spectrometers with isolated attosecond pulses or pulse trains. As the inverse process of photoionization, photorecombination is known to exhibit similar time delays, which can arise from multielectron interaction and electronic structure. Here, we demonstrate that, by perturbing the recollision process with a co-phased weak field, photorecombination delay due to multielectron interaction can be measured entirely optically by observing the modulation of the emitted extreme ultraviolet (XUV) radiation with respect to the delay between the driving and perturbing fields. We first investigate this by simulating recollision in the one-dimensional helium atom and study recollision-induced Fano resonance excitation. We then extend this work to more realistic systems and investigate recollision and the giant resonance in xenon using time-dependent density functional theory. Our results agree with experimental results measured in similar experimental conditions, showing the effect of the giant dipole resonance in xenon has on the recolliding electron. This work opens a new path to the study of strong-field induced ultrafast electron correlation by employing an all-optical measurement method. |
Wednesday, June 2, 2021 3:12PM - 3:24PM Live |
M02.00007: Channel coupling in molecular photoemission delays Anna L Wang, Taran Driver, Andrei Kamalov, Philip H Bucksbaum, James P Cryan Photoemission delays are a measurement of the phase distortion of an electronic wavepacket as it escapes a cationic potential during photoionization. Electron-electron and electron-nuclear interactions can couple multiple ionization channels, altering the measured photoionization phase and introducing a delay compared to the expected single channel photoemission time. As a result, photoemission delays are a sensitive probe of dynamic molecular phenomena that can be hard to detect with partial photoionization cross-sections. We study photoionization in both the XUV and X-ray regimes for several molecular targets that display different time dependent potential features, such as fast nuclear motion, shape resonance, and core-ionization. These diverse set of ionization phenomena result in channel coupling that we observe through the photoemission delay. |
Wednesday, June 2, 2021 3:24PM - 3:36PM Live |
M02.00008: Attosecond spectroscopy of size-resolved water clusters Saijoscha Heck, Xiaochun Gong, Denis Jelovina, Conaill Perry, kristina zinchenko, Hans Jakob Woerner Electron dynamics in water are of fundamental importance for a broad range of phenomena, |
Wednesday, June 2, 2021 3:36PM - 3:48PM Live |
M02.00009: Photorecombination Time Delays characterization with all-optical method Chunmei Zhang, Graham G Brown, Dong Hyuk Ko, Paul B Corkum Measuring the photoionization time delay between electrons from different orbitals is one of the most important accomplishments of attosecond science. Photoionization time delay is usually measured using single attosecond XUV pulses in a streaking experiment or using an attosecond XUV pulse train in a RABBIT experiment. However, the measured delay is the superposition of all possible contributions to ionization and may include delays associated with multiple channels, the ionizing pulse, ionic and electronic structural effects, multielectron interaction, and Coulomb-laser coupling. Deconvolving these disparate contributions is difficult. Here, we show that, by characterizing recollision dynamics entirely optically, photorecombination time delays from individual pathways to recombination can be measured without obfuscation from ionic structural and propagation effects. This work opens a path to the all-optical measurement of ultrafast electron dynamics and photorecombination time delays due to electronic structure, multielectron interaction, and strong-field driven dynamics in complex molecular systems and correlated solid-state systems. |
Wednesday, June 2, 2021 3:48PM - 4:00PM Live |
M02.00010: Molecular RABITT time delays studied using the time-independent multi-photon R-matrix method Jakub Benda, Zdenek Masin, Jimena D Gorfinkiel Numerical simulations of multiphoton processes in atoms and molecules typically involve solution of the computationally demanding time-dependent Schrödinger equation. Recently, we developed a computationally efficient time-independent theoretical method for calculation of ionization amplitudes for multiphoton ionization of atoms and molecules, including the above-threshold ionization of arbitrary order. This method is based on the R-matrix splitting of the configuration space to inner region, where multi-electron methods of complete active space type are used, and the outer region, whose contributions are treated analytically. |
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