Bulletin of the American Physical Society
53rd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 67, Number 7
Monday–Friday, May 30–June 3 2022; Orlando, Florida
Session H10: Focus Session: Ultrafast Structural Dynamics of MoleculesFocus Live Streamed
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Chair: Michael Schuurman, Ottawa Room: Grand Ballroom D |
Wednesday, June 1, 2022 8:00AM - 8:30AM |
H10.00001: Towards new experiments in ultrafast x-ray scattering Invited Speaker: Adam Kirrander Ultrafast time-resolved x-ray scattering on free molecules in the gas phase provides a window onto the ultrafast dynamics induced by photoexcitation of molecules. Significant advances in resolving transient nuclear structural dynamics in excited molecules have already been made. However, scattering provides rich information beyond structure and the rapid advances at x-ray free electron lasers (XFELs) are yielding highly resolved and information rich signals. We will discuss the types of experiments that one can anticipate over the coming years, and the computational tools that will allow us to interpret these experiments. Detailed simulations of potential experiments allow us to assess the physical insights gained from different types of scattering. Strikingly, the distinction between scattering techniques for structural dynamics on one hand and spectroscopy on the other becomes increasingly blurred. This points towards future directions that may include the characterization of valence electronic states and direct measurements of the effects of electron correlation and coherence using x-ray scattering. |
Wednesday, June 1, 2022 8:30AM - 8:42AM |
H10.00002: Revealing ultrafast proton transfer dynamics in ionized aqueous urea through time-resolved x-ray absorption spectra and ab initio simulations Yashoj Shakya, Ludger Inhester, Zhong Yin, Yi-Ping Chang, Tadas Balciunas, Jean-Pierre Wolf, Hans Jakob Woerner, Robin Santra Probing the early dynamics of chemical systems following ionization is essential for our understanding of radiation damage. The advent of FELs and advances in high harmonic generation (HHG) has shown that time-resolved x-ray absorption spectroscopy (TRXAS) on a femtosecond timescale can provide crucial insights into the ultrafast processes occurring upon ionization due to its element-specificity. However, to get a clear interpretation of the dynamical features in the spectra, one often has to reply on theoretical simulations. |
Wednesday, June 1, 2022 8:42AM - 9:12AM |
H10.00003: Imaging proton transfer dynamics in o-nitrophenol by Ultrafast Electron Diffraction Invited Speaker: Joao Pedro Figueira Nunes Many important biological and chemical reactions are initiated by the transfer of a proton from a donor to an acceptor group within a molecule. These intramolecular proton transfer (IPT) reactions mediate fundamental biological processes, such as the oxidation of water during plant photosynthesis, the light-driven proton pump bacteriorhodopsin and light emission from green fluorescent protein. Moreover, IPT reactions have found wide industrial applicability as: fluorescence-based sensors, laser dyes, organic light-emitting diodes, solar collectors and molecular logic gates. Despite its biological and industrial importance, the structural rearrangements mediating IPT reactions had, until now, never been imaged on the atomic length and time scales. |
Wednesday, June 1, 2022 9:12AM - 9:24AM |
H10.00004: Sensitivity of inner-shell photoelectron spectroscopy to non-Born-Oppenheimer and photodissociation dynamics in polyatomic molecules Ian Gabalski, Felix Allum, Issaka Seidu, Mathew Britton, Michael S Schuurman, Ruaridh Forbes Gas-phase CS2 photoexcited at 200 nm exhibits many general features of complex photodissociation: vibrational mode coupling, internal conversion, and intersystem crossing. The molecule initially undergoes bending and symmetric stretching motion before coupling to asymmetric stretch motion leading to dissociation of atomic sulfur. In the present work, we explore the ability of time-resolved inner-shell photoelectron spectroscopy at the sulfur 2p site to investigate such complex photodynamics. |
Wednesday, June 1, 2022 9:24AM - 9:36AM |
H10.00005: Extracting site-specific information about bond rearrangement during ethanol photofragmentation Eleanor Weckwerth, Eric Wells, Travis Severt, Balram Kaderiya, Peyman Feizollah, Bethany C Jochim, Farzaneh Ziaee, Kurtis D Borne, Kanaka Raju P., Kevin D Carnes, Daniel Rolles, Artem Rudenko, Itzik Ben-Itzhak Ethanol (CH3CH2OH) has three locations for hydrogen atoms: the hydrogen that is part of the hydroxyl group, the three β-hydrogens attached to the carbon atom opposite the hydroxyl group, and the two α-hydrogens attached to the central carbon atom. When studying bond rearrangement initiated by an ultrafast laser pulse, such as the production of H3+ photofragments, it is desirable to be able to know which sites contribute hydrogen atoms to the final product. Here we describe a technique that combines COLTRIMS data obtained using different isotopologues of ethanol under identical laser pulse conditions (800 nm central wavelength, 3.0×1014 W/cm2 peak intensity, 23 fs FWHM) to extract site-specific data about the formation of H3+ following double-ionization of the parent molecule. |
Wednesday, June 1, 2022 9:36AM - 9:48AM |
H10.00006: Competition between hydrogen elimination and deprotonation in CDn+ fragmentation by intense ultrashort laser pulses* Naoki Iwamoto, Travis Severt, Tiana A Townsend, Kevin D Carnes, Itzik Ben-Itzhak We investigated hydrogen elimination (CDn+ ® CDn-1+ + D) and deprotonation (CDn+ ® CDn-1 + D+) processes in CDn+ fragmentation by focusing intense ultrashort laser pulses‡ onto fast (keV) CDn+ ion beam targets. The laser induced fragments, including neutral fragments, are measured in coincidence, and their 3-dimentional momenta are evaluated. One of the main goals of this study is to determine the relative importance of hydrogen elimination versus deprotonation. We also compare the kinetic energy release (KER) and angular distributions of these fragmentation processes. Curiously, following the ionization of CD3+ and in addition to the expected deprotonation (CD32+ ® CD2+ + D+), hydrogen elimination (CD32+ ® CD22+ + D) was also observed, though far less frequently. |
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