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 X02: Focus Session: Probing and Controlling Matter with Intense LightFocus Live
|
Hide Abstracts |
Chair: Loren Greenman, Kansas State University |
Friday, June 4, 2021 8:00AM - 8:30AM Live |
X02.00001: Nonlinear light-matter interaction with intense XUV free-electron lasers Invited Speaker: Christian Ott The optical response of matter to external light stimuli is encoded in their absorption spectra and gives access to the quantum dynamics of atoms and molecules. In the extreme ultraviolet (XUV) and x-ray domain this includes site-specific resonant transitions, making a clear identification possible and attributing them to individual excitations of bound electrons. With the availability of intense XUV/x-ray light from free-electron lasers these transitions can be further modified, thus opening up new possibilities for deliberately controlling the underlying quantum dynamics in a site-specific manner. In this regard we have performed a series of experiments employing all-XUV-optical pump-probe transient absorption spectroscopy with the FLASH free-electron laser in Hamburg, which is based on self-amplified spontaneous emission (SASE), in order to probe and control XUV nonlinear light-matter interaction in atoms and small molecules [1]. For instance, we have successfully demonstrated the direct dressing of a two-electron transition in helium, resolving Fano lineshape asymmetry changes that can be attributed to the strong coupling of the ground state to an autoionizing doubly excited state [2]. In neon, FEL-induced Stark shifts can be identified in the measured absorption spectra as well as resolving coherence signatures on the few-meV spectral and few-fs temporal scale [3]. These measurements thus also allowed us to quantify the average spectro-temporal chirp of SASE-FEL pulses [4]. With proven sensitivity to spectral interference structures and combining both high temporal and spectral resolution, nonlinear all-XUV-optical transient absorption spectroscopy can be regarded as a key step towards the implementation of multi-color multi-dimensional spectroscopy methodologies in the XUV and x-ray domain. |
Friday, June 4, 2021 8:30AM - 8:42AM Live |
X02.00002: Multi-electron interaction control in molecules using ultrashort laser pulses Patrick Rupprecht, Lennart Aufleger, Simon Heinze, Alexander Magunia, Thomas Ding, Marc Rebholz, Stefano Amberg, Nikola Mollov, Felix Henrich, Maurits Haverkort, Christian Ott, Thomas Pfeifer While electron-electron interactions play a fundamental role in any atom beyond hydrogen, they also govern molecular structure and reactivity. We introduce and experimentally demonstrate a general concept to control multi-electron interaction by intense, ultrashort laser fields. In particular, strong coupling to excited states allows to modify the effective exchange energy by infrared (IR) induced valence orbital mixing. For a proof-of-principle, we focus on the sulfur hexafluoride molecule, SF6, considering the coupling of a sulfur 2p core hole with a valence excited electron on the few-femtosecond timescale, using a combination of soft x-ray and IR laser pulses. The IR laser intensity represents a control knob to tune the effective exchange interaction energy, resulting in a characteristic change in the spin-orbit-split oscillator strength ratio that is directly quantified in the x-ray absorption spectroscopy experiment. This is conducted on a purely electronic level without depending on nuclear motion or significant population transfer. Besides describing the underlying physics with a mechanistic fit model, these findings are validated by an ab-initio quantum-mechanical many-body simulation. Such direct control of effective electronic interactions and correlation is a significant step towards laser-directed chemistry on the fundamental electronic level with single-atomic site selectivity. |
Friday, June 4, 2021 8:42AM - 8:54AM Live |
X02.00003: Site-Specific Generation of Excited State Wavepackets with High-Intensity Attosecond X-rays Adam E Fouda, Phay J Ho Non-linear interactions with strong-field, ultrafast x-rays, made possible by recent XFEL developments, can produce coherent superpositions of valence excited states. This offers the potential to observe charge migration dynamics prior to excited state nuclear motion. The broad-band, high-field nature of the required pulses results in a multitude of accessible excited states of both valence and Rydberg nature. This work uses multiconfigurational quantum chemistry in conjunction with the time-dependent Schrödinger equation to evaluate the population transfer dynamics in impulsive stimulated x-ray Raman scattering on nitric oxide, following the recent experimental and theoretical advances at the oxygen K-edge [1]. A comparative assessment is made between the oxygen and nitrogen K-edges, using chemical insights gained from the resonant inelastic x-ray scattering [2]. Effects from the electronic structure calculations and pulse conditions on the population transfer are explored, highlighting complexities attributed to the Rabi frequency. High state-selectivity for Rydberg-valence excited states is achieved via an orthogonally polarized two-color stimulated-RIXS setup. |
Friday, June 4, 2021 8:54AM - 9:24AM Live |
X02.00004: Exploiting Coherences to Probe Strong-Field Molecular Ionization Dynamics Invited Speaker: Robert R Jones Ionization is a common central feature of strong-field molecular physics. It serves as the critical first step in high-harmonic and attosecond pulse generation, and can establish electronic coherences and charge migration dynamics in the molecular ion. Not surprisingly, the orientation of a molecule relative to the polarization of an intense ionizing laser can play an essential role in inducing, controlling, and probing the intramolecular dynamics resulting from strong-field ionization. Hence, it is important to understand that orientation dependence. One approach for measuring angle-dependent (non-dissociative) ionization yields is to preferentially orient the target molecules in the laboratory frame, prior to their exposure to the intense ionizing field. Depending on the orientation technique, the effectiveness of this approach can be limited by the degree of achievable orientation, the presence of strong orienting fields during the ionization pulse, and/or background ionization induced by the orienting field. We have recently explored a different method, using an asymmetric 2-color ionizing field and the anisotropic ionization process itself to coherently alter the rotational distributions in both the molecular ions and surviving neutrals. The angular distribution of ion fragments produced via Coulomb explosion in a more intense time-delayed probe, is then used to track the coherent motion of the rotational wavepackets. For linear and symmetric top molecules, which exhibit pronounced rotational revival structures during their evolution, one can distinguish the rotational motion of neutral and ion species by their different revival times. By fitting the observed rotational revivals to a model that includes both strong-field ionization anisotropy and non-ionizing Raman and hyper-Raman rotational redistribution, the angle-dependent ionization rate can be extracted. The method can, in principal, be extended to determine the angle-dependent ionization rate into different electronic, and perhaps even vibrational, states of the ion. |
Friday, June 4, 2021 9:24AM - 9:36AM Live |
X02.00005: Probing and controlling autoionizing polaritons in atomic ionization Nathan Harkema, Coleman B Cariker, Sergio Yanez-Pagans, Moniruzzaman Shaikh, Islam S Shalaby, Luca Argenti, Arvinder S Sandhu Theoretical studies of laser dressed autoionizing states have predicted control and stabilization against ionization under specific conditions. Here we use attosecond extreme ultraviolet transient absorption spectroscopy to investigate the evolution of autoionizing states in argon atom dressed by a tunable femtosecond IR laser pulse. We observe avoided crossings between the 3s$^{-1}$4p and several light-induced states, indicating the formation of polaritons. The properties of these autoionizing polaritons, entangled states of light and Auger resonances are largely unexplored. We show evidence of stabilization of the polaritons against ionization by using time-delay, frequency detuning, and laser intensity as control parameters. The experimental results match well with ab-initio theoretical calculations. We show that this stabilization is due to the destructive interference between the Auger decay and the radiative ionization of the polaritonic components. These results open the doors for optical control of continuum states in polyelectronic systems. |
Friday, June 4, 2021 9:36AM - 9:48AM Live |
X02.00006: Light-Induced Valleytronics In Pristine Graphene Gopal Dixit, Mrudul Muraleedharan Shylaja, Misha Ivanov, Alvaro Jimenez-Galan Graphene, the first monolayer material, has achieved significant attraction in both applied and fundamental sciences in the past decade [1]. The charge carriers in graphene, also known as Dirac fermions, have peculiar properties from the linear dispersion and zero bandgap of the material. |
Friday, June 4, 2021 9:48AM - 10:00AM Live |
X02.00007: Coherent manipulation of matter-waves on femtosecond timescales Philipp Wessels-Staarmann, Bernhard Ruff, Tobias Kroker, Markus Drescher, Klaus Sengstock, Juliette Simonet Bridging the worlds of ultrafast physics and ultracold quantum matter opens new pathways to manipulate macroscopic wave functions on femtosecond timescales and to control the formation of ions and electrons in a quantum gas [1, 2] towards the creation of hybrid quantum systems. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700