1
|
Ellis JL, Hickstein DD, Xiong W, Dollar F, Palm BB, Keister KE, Dorney KM, Ding C, Fan T, Wilker MB, Schnitzenbaumer KJ, Dukovic G, Jimenez JL, Kapteyn HC, Murnane MM. Materials Properties and Solvated Electron Dynamics of Isolated Nanoparticles and Nanodroplets Probed with Ultrafast Extreme Ultraviolet Beams. J Phys Chem Lett 2016; 7:609-615. [PMID: 26807653 DOI: 10.1021/acs.jpclett.5b02772] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We present ultrafast photoemission measurements of isolated nanoparticles in vacuum using extreme ultraviolet (EUV) light produced through high harmonic generation. Surface-selective static EUV photoemission measurements were performed on nanoparticles with a wide array of compositions, ranging from ionic crystals to nanodroplets of organic material. We find that the total photoelectron yield varies greatly with nanoparticle composition and provides insight into material properties such as the electron mean free path and effective mass. Additionally, we conduct time-resolved photoelectron yield measurements of isolated oleylamine nanodroplets, observing that EUV photons can create solvated electrons in liquid nanodroplets. Using photoemission from a time-delayed 790 nm pulse, we observe that a solvated electron is produced in an excited state and subsequently relaxes to its ground state with a lifetime of 151 ± 31 fs. This work demonstrates that femotosecond EUV photoemission is a versatile surface-sensitive probe of the properties and ultrafast dynamics of isolated nanoparticles.
Collapse
Affiliation(s)
- Jennifer L Ellis
- JILA-NIST and Department of Physics, University of Colorado , 440 UCB, Boulder, Colorado 80309, United States
| | - Daniel D Hickstein
- JILA-NIST and Department of Physics, University of Colorado , 440 UCB, Boulder, Colorado 80309, United States
| | - Wei Xiong
- JILA-NIST and Department of Physics, University of Colorado , 440 UCB, Boulder, Colorado 80309, United States
- Department of Chemistry and Biochemistry, University of California San Diego , La Jolla, California 92093, United States
| | - Franklin Dollar
- JILA-NIST and Department of Physics, University of Colorado , 440 UCB, Boulder, Colorado 80309, United States
| | - Brett B Palm
- CIRES and Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309, United States
| | - K Ellen Keister
- JILA-NIST and Department of Physics, University of Colorado , 440 UCB, Boulder, Colorado 80309, United States
| | - Kevin M Dorney
- JILA-NIST and Department of Physics, University of Colorado , 440 UCB, Boulder, Colorado 80309, United States
| | - Chengyuan Ding
- JILA-NIST and Department of Physics, University of Colorado , 440 UCB, Boulder, Colorado 80309, United States
| | - Tingting Fan
- JILA-NIST and Department of Physics, University of Colorado , 440 UCB, Boulder, Colorado 80309, United States
| | - Molly B Wilker
- Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309, United States
| | - Kyle J Schnitzenbaumer
- Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309, United States
| | - Gordana Dukovic
- Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309, United States
| | - Jose L Jimenez
- CIRES and Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309, United States
| | - Henry C Kapteyn
- JILA-NIST and Department of Physics, University of Colorado , 440 UCB, Boulder, Colorado 80309, United States
| | - Margaret M Murnane
- JILA-NIST and Department of Physics, University of Colorado , 440 UCB, Boulder, Colorado 80309, United States
| |
Collapse
|
2
|
Marsalek O, Elles CG, Pieniazek PA, Pluhařová E, VandeVondele J, Bradforth SE, Jungwirth P. Chasing charge localization and chemical reactivity following photoionization in liquid water. J Chem Phys 2012; 135:224510. [PMID: 22168706 DOI: 10.1063/1.3664746] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The ultrafast dynamics of the cationic hole formed in bulk liquid water following ionization is investigated by ab initio molecular dynamics simulations and an experimentally accessible signature is suggested that might be tracked by femtosecond pump-probe spectroscopy. This is one of the fastest fundamental processes occurring in radiation-induced chemistry in aqueous systems and biological tissue. However, unlike the excess electron formed in the same process, the nature and time evolution of the cationic hole has been hitherto little studied. Simulations show that an initially partially delocalized cationic hole localizes within ~30 fs after which proton transfer to a neighboring water molecule proceeds practically immediately, leading to the formation of the OH radical and the hydronium cation in a reaction which can be formally written as H(2)O(+) + H(2)O → OH + H(3)O(+). The exact amount of initial spin delocalization is, however, somewhat method dependent, being realistically described by approximate density functional theory methods corrected for the self-interaction error. Localization, and then the evolving separation of spin and charge, changes the electronic structure of the radical center. This is manifested in the spectrum of electronic excitations which is calculated for the ensemble of ab initio molecular dynamics trajectories using a quantum mechanics/molecular mechanics (QM∕MM) formalism applying the equation of motion coupled-clusters method to the radical core. A clear spectroscopic signature is predicted by the theoretical model: as the hole transforms into a hydroxyl radical, a transient electronic absorption in the visible shifts to the blue, growing toward the near ultraviolet. Experimental evidence for this primary radiation-induced process is sought using femtosecond photoionization of liquid water excited with two photons at 11 eV. Transient absorption measurements carried out with ~40 fs time resolution and broadband spectral probing across the near-UV and visible are presented and direct comparisons with the theoretical simulations are made. Within the sensitivity and time resolution of the current measurement, a matching spectral signature is not detected. This result is used to place an upper limit on the absorption strength and/or lifetime of the localized H(2)O(+) ((aq)) species.
Collapse
Affiliation(s)
- Ondrej Marsalek
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic and Center for Biomolecules and Complex Molecular Systems, Flemingovo nám. 2, 16610 Prague 6, Czech Republic
| | | | | | | | | | | | | |
Collapse
|