Title: Ultrafast time-resolved x-ray absorption spectroscopy of ionized urea and its dimer through ab initio nonadiabatic dynamics

Abstract

Investigating the early dynamics of chemical systems following ionization is essential for our understanding of radiation damage. However, experimental as well as theoretical investigations are very challenging due to the complex nature of these processes. Time-resolved x-ray absorption spectroscopy on a femtosecond timescale, in combination with appropriate simulations, is able to provide crucial insights into the ultrafast processes that occur upon ionization due to its element-specific probing nature. In this theoretical study, we investigate the ultrafast dynamics of valence-ionized states of urea and its dimer employing Tully’s fewest switches surface hopping approach using Koopmans’ theorem to describe the ionized system. We demonstrate that following valence ionization through a pump pulse, the time-resolved x-ray absorption spectra at the carbon, nitrogen, and oxygen K-edges reveal rich insights into the dynamics. Excited states of the ionized system give rise to time-delayed blueshifts in the x-ray absorption spectra as a result of electronic relaxation dynamics through nonadiabatic transitions. Moreover, our statistical analysis reveals specific structural dynamics in the molecule that induce time-dependent changes in the spectra. For the urea monomer, we elucidate the possibility to trace effects of specific molecular vibrations in the time-resolved x-ray absorption spectra. For the urea dimer, where ionization triggersmore » a proton transfer reaction, we show how the x-ray absorption spectra can reveal specific details on the progress of proton transfer.« less

Authors:

Shakya, Yashoj  ^[1];

• Search DOE PAGES for author "Shakya, Yashoj"
• Search DOE PAGES for ORCID "0000-0002-7054-9344"

Inhester, Ludger  ^[2];

• Search DOE PAGES for author "Inhester, Ludger"
• Search DOE PAGES for ORCID "0000-0003-1417-4151"

Arnold, Caroline  ^[3];

• Search DOE PAGES for author "Arnold, Caroline"
• Search DOE PAGES for ORCID "0000-0002-9458-1517"

Welsch, Ralph  ^[2];

• Search DOE PAGES for author "Welsch, Ralph"
• Search DOE PAGES for ORCID "0000-0001-9995-7926"

Santra, Robin  ^[3]

• Search DOE PAGES for author "Santra, Robin"
• Search DOE PAGES for ORCID "0000-0002-1442-9815"

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+ Show Author Affiliations

1. Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science; Universität Hamburg (Germany). Dept. of Physics
2. Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science; Hamburg Centre for Ultrafast Imaging (Germany)
3. Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Center for Free-Electron Laser Science; Universität Hamburg (Germany). Dept. of Physics; Hamburg Centre for Ultrafast Imaging (Germany)

Publication Date:

Wed May 12 00:00:00 EDT 2021

Research Org.:

Kansas State Univ., Manhattan, KS (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division

OSTI Identifier:

1816548

Grant/Contract Number:  

SC0019451

Resource Type:

Accepted Manuscript

Journal Name:

Structural Dynamics

Additional Journal Information:

Journal Volume: 8; Journal Issue: 3; Journal ID: ISSN 2329-7778

Publisher:

American Crystallographic Association/AIP

Country of Publication:

United States

Language:

English

Subject:

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; X-ray absorption spectroscopy; Quantum chemical dynamics; Organic compounds Transfer reactions; Tully's fewest switches surface hopping algorithm; Ultrafast processes; Ab initio electronic structure calculations; Koopmans' theorem; Radiation damage