1
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Tsizin S, Ban L, Chasovskikh E, Yoder BL, Signorell R. Valence photoelectron imaging of molecular oxybenzone. Phys Chem Chem Phys 2024; 26:19236-19246. [PMID: 38957915 PMCID: PMC11253247 DOI: 10.1039/d3cp06224d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Accepted: 06/18/2024] [Indexed: 07/04/2024]
Abstract
An oxybenzone molecule in the gas phase was characterized by mass spectrometry and angle-resolved photoelectron spectroscopy, using both single and multiphoton ionization schemes. A tabletop high harmonic generation source with a monochromator was used for single-photon ionization of oxybenzone with photon energies of up to 35.7 eV. From this, vertical ionization and appearance energies, as well as energy-dependent anisotropy parameters were retrieved and compared with the results from DFT calculations. For two-photon ionization using 4.7 eV light, we found a higher appearance energy than in the extreme ultraviolet (EUV) case, highlighting the possible influence of an intermediate state on the photoionization process. We found no differences in the mass spectra when ionizing oxybenzone by single-photons between 17.2 and 35.7 eV. However, for the multiphoton ionization, the fragmentation process was found to be sensitive to the photoionization order and laser intensity. The "softest" method was found to be two-photon ionization using 4.7 eV light, which led to no measurable fragmentation up to an intensity of 5 × 1012 W cm-2.
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Affiliation(s)
- Svetlana Tsizin
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2., CH-8093 Zürich, Switzerland.
| | - Loren Ban
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2., CH-8093 Zürich, Switzerland.
| | - Egor Chasovskikh
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2., CH-8093 Zürich, Switzerland.
| | - Bruce L Yoder
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2., CH-8093 Zürich, Switzerland.
| | - Ruth Signorell
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2., CH-8093 Zürich, Switzerland.
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2
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Ban L, Tang H, Heitland J, West CW, Yoder BL, Thanopulos I, Signorell R. Ion imaging of spatially inhomogeneous nanoplasmas in NaCl particles. NANOSCALE 2024; 16:5695-5705. [PMID: 38407309 PMCID: PMC10939055 DOI: 10.1039/d3nr06368b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Accepted: 02/17/2024] [Indexed: 02/27/2024]
Abstract
Studying photoemission from free, unsupported aerosol particles is a powerful method for gaining insight into light-matter interactions at the nanoscale. We used single-shot velocity map imaging to experimentally measure kinetic energy and angular distributions of ions emitted following interaction of sub-micrometer NaCl particles with femtosecond pulses of near infrared (NIR, 800 nm) and ultraviolet (UV, 266 nm) light. We combined this with time-dependent simulations of light propagation through the particles and a rate equation approach to computationally address the origin of the observed ion emission. For both NIR and UV pulses, ion emission is caused by the formation of an under-dense nanoplasma with similar densities, although using an order of magnitude weaker UV intensities. Such conditions result in remarkably similar ion fragments with similar kinetic energies, and no obvious influence of the plasma formation mechanism (photoionization or collisional ionization). Our data suggests that Coulomb explosion does not play a significant role for ion emission, and we discuss alternative mechanisms that can lead to material ablation from under-dense nanoplasma. Finally, we show how finite size effects play an important role in photoemission through generation of spatially inhomogeneous nanoplasmas, which result in asymmetric ion emission that depends on particle size and laser wavelength. By utilizing the single-particle information available from our experiments, we show how finite size effects and inhomogeneous nanoplasma formation can be exploited to retrieve the size and orientation of individual submicrometer aerosol particles.
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Affiliation(s)
- Loren Ban
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, Zürich 8093, Switzerland.
| | - Hanchao Tang
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, Zürich 8093, Switzerland.
| | - Jonas Heitland
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, Zürich 8093, Switzerland.
| | - Christopher W West
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, Zürich 8093, Switzerland.
| | - Bruce L Yoder
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, Zürich 8093, Switzerland.
| | - Ioannis Thanopulos
- Department of Materials Science, University of Patras, Eupalinou 5, 26504 Rio, Patras, Greece
| | - Ruth Signorell
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, Zürich 8093, Switzerland.
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3
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Parmentier EA, Corral Arroyo P, Gruseck R, Ban L, David G, Signorell R. Charge Effects on the Photodegradation of Single Optically Trapped Oleic Acid Aerosol Droplets. J Phys Chem A 2022; 126:4456-4464. [PMID: 35767023 PMCID: PMC9289876 DOI: 10.1021/acs.jpca.2c01370] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
![]()
It has recently been
reported that reactions can occur faster in
microdroplets than in extended condensed matter. The electric charge
of droplets has also been suggested as a possible cause of this phenomenon.
Here, we investigate the influence of electric charges on the photodegradation
of single, optically trapped oleic acid aerosol droplets in the absence
of other reactive species. The temporal evolution of the chemical
composition and the size of droplets with charge states ranging from
0 to 104 elementary charges were retrieved from Raman spectra
and elastic light scattering, respectively. No influence of the droplet
charge was observed, either on the chemical composition or on the
kinetics. Based on a kinetic multilayer model, we propose a reaction
mechanism with the photoexcitation of oleic acid into an excited state,
subsequent decay into intermediates and further photoexcitation of
intermediates and their decay into nonvolatile and volatile products.
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Affiliation(s)
- Evelyne A Parmentier
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
| | - Pablo Corral Arroyo
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
| | - Richard Gruseck
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
| | - Loren Ban
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
| | - Grégory David
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
| | - Ruth Signorell
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
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4
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Signorell R, Winter B. Photoionization of the aqueous phase: clusters, droplets and liquid jets. Phys Chem Chem Phys 2022; 24:13438-13460. [PMID: 35510623 PMCID: PMC9176186 DOI: 10.1039/d2cp00164k] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
This perspective article reviews specific challenges associated with photoemission spectroscopy of bulk liquid water, aqueous solutions, water droplets and water clusters. The main focus lies on retrieving accurate energetics and photoelectron angular information from measured photoemission spectra, and on the question how these quantities differ in different aqueous environments. Measured photoelectron band shapes, vertical binding energies (ionization energies), and photoelectron angular distributions are influenced by various phenomena. We discuss the influences of multiple energy-dependent electron scattering in aqueous environments, and we discuss different energy referencing methods, including the application of a bias voltage to access absolute energetics of solvent and solute. Recommendations how to account for or minimize the influence of electron scattering are provided. The example of the hydrated electron in different aqueous environments illustrates how one can account for electron scattering, while reliable methods addressing parasitic potentials and proper energy referencing are demonstrated for ionization from the outermost valence orbital of neat liquid water. This perspective article reviews specific challenges associated with photoemission spectroscopy of bulk liquid water, aqueous solutions, water droplets and water clusters.![]()
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Affiliation(s)
- Ruth Signorell
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland.
| | - Bernd Winter
- Molecular Physics Department, Fritz-Haber-Institute der Max-Planck-Gesellschaft, Faradayweg 4-6, 14196 Berlin, Germany.
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Ban L, Tang H, Yoder BL, Signorell R. Time-dependent photoemission from droplets: influence of size and charge on the photophysics near the surface. Faraday Discuss 2022; 236:461-484. [PMID: 35507329 PMCID: PMC9408814 DOI: 10.1039/d1fd00108f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Photoemission from submicrometer droplets containing a mixture of dioctyl phthalate and dioctyl sebacate was investigated by femtosecond and nanosecond photoionization. Photoelectron spectra recorded after ionization with single 4.7 eV femtosecond or nanosecond laser pulses showed marked differences between the two cases. These differences were attributed to ionization of long-lived states which only occurred within the duration of the nanosecond pulse. The tentative assignment of the long-lived states to dioctyl phthalate triplet states is discussed. A nanosecond–femtosecond pump–probe scheme using 4.7 eV (pump) and 3.1 eV (probe) pulses was used to investigate the decay dynamics of these long-lived states. The dynamics showed an accelerated decay rate at higher dioctyl phthalate concentrations. Furthermore, the dependence of the decay dynamics on droplet size and charge was investigated. The decay of the long-lived states was found to be faster in smaller droplets as well as in neutral droplets compared with both positively and negatively charged droplets. Possible mechanisms to explain these observations and the dominance of contributions from the droplets surface are discussed. Time-resolved photoemission spectroscopy is used to study the photophysics of droplets containing dioctyl phthalate. Long-lived excited states survive longer at lower phthalate concentrations, and in larger or electrically charged droplets.![]()
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Affiliation(s)
- Loren Ban
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog Weg 2, CH-8093 Zürich, Switzerland.
| | - Hanchao Tang
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog Weg 2, CH-8093 Zürich, Switzerland.
| | - Bruce L Yoder
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog Weg 2, CH-8093 Zürich, Switzerland.
| | - Ruth Signorell
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog Weg 2, CH-8093 Zürich, Switzerland.
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Gadeyne T, Zhang P, Schild A, Wörner HJ. Low-energy electron distributions from the photoionization of liquid water: a sensitive test of electron mean-free paths. Chem Sci 2022; 13:1675-1692. [PMID: 35282614 PMCID: PMC8826766 DOI: 10.1039/d1sc06741a] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 01/06/2022] [Indexed: 11/21/2022] Open
Abstract
The availability of accurate mean free paths for slow electrons (<50 eV) in water is central to the understanding of many electron-driven processes in aqueous solutions, but their determination poses major challenges to experiment and theory alike. Here, we describe a joint experimental and theoretical study demonstrating a novel approach for testing, and, in the future, refining such mean free paths. We report the development of Monte-Carlo electron-trajectory simulations including elastic and inelastic electron scattering, as well as energy loss and secondary-electron production to predict complete photoelectron spectra of liquid water. These simulations are compared to a new set of photoelectron spectra of a liquid-water microjet recorded over a broad range of photon energies in the extreme ultraviolet (20–57 eV). Several previously published sets of scattering parameters are investigated, providing direct and intuitive insights on how they influence the shape of the low-energy electron spectra. A pronounced sensitivity to the escape barrier is also demonstrated. These simulations considerably advance our understanding of the origin of the prominent low-energy electron distributions in photoelectron spectra of liquid water and clarify the influence of scattering parameters and the escape barrier on their shape. They moreover describe the reshaping and displacement of low-energy photoelectron bands caused by vibrationally inelastic scattering. Our work provides a quantitative basis for the interpretation of the complete photoelectron spectra of liquids and opens the path to fully predictive simulations of low-energy scattering in liquid water. Our study reveals the detailed influence of elastic and inelastic mean-free paths on the complete photoelectron spectra of liquid water, including the low-energy electron distributions and the reshaping of the primary photoelectron bands.![]()
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Affiliation(s)
- Titouan Gadeyne
- Laboratory for Physical Chemistry, ETH Zürich Vladimir-Prelog-Weg 2 8093 Zürich Switzerland
- Département de Chimie, École Normale Supérieure, PSL University 75005 Paris France
| | - Pengju Zhang
- Laboratory for Physical Chemistry, ETH Zürich Vladimir-Prelog-Weg 2 8093 Zürich Switzerland
| | - Axel Schild
- Laboratory for Physical Chemistry, ETH Zürich Vladimir-Prelog-Weg 2 8093 Zürich Switzerland
| | - Hans Jakob Wörner
- Laboratory for Physical Chemistry, ETH Zürich Vladimir-Prelog-Weg 2 8093 Zürich Switzerland
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7
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Hartweg S, Garcia GA, Božanić DK, Nahon L. Condensation Effects on Electron Chiral Asymmetries in the Photoionization of Serine: From Free Molecules to Nanoparticles. J Phys Chem Lett 2021; 12:2385-2393. [PMID: 33660503 DOI: 10.1021/acs.jpclett.1c00258] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Structural changes at the molecular level, occurring at the onset of condensation, can be probed by angle-resolved valence photoelectron spectroscopy, which is inherently sensitive to the electronic structure. For larger condensed systems like aerosol particles, the observation of intrinsic angular anisotropies in photoemission (β parameters) is challenging due to the strong reduction of their magnitude by electron transport effects. Here, we use a less common, more sensitive observable in the form of the chiral asymmetry parameter to perform a comparative study of the VUV photoelectron spectroscopy and photoelectron circular dichroism (PECD) between pure gas phase enantiomers of the amino acid serine and their corresponding homochiral nanoparticles. We observe a relatively large (1%) and strongly kinetic energy-dependent asymmetry, discussed in terms of the emergence of local order and conformational changes potentially counterbalancing the loss of angular information due to electron transport scattering. This demonstrates the potential of PECD as a sensitive probe of the condensation effects from the gas phase to bulk-like chiral aerosol particles surpassing the potential of conventional photoemission observables such as β parameters.
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Affiliation(s)
- Sebastian Hartweg
- Synchrotron SOLEIL, l'Orme des Merisiers, Saint Aubin BP 48, 91192 Cedex, Gif sur Yvette, France
| | - Gustavo A Garcia
- Synchrotron SOLEIL, l'Orme des Merisiers, Saint Aubin BP 48, 91192 Cedex, Gif sur Yvette, France
| | - Dušan K Božanić
- Department of Radiation Chemistry and Physics, "VINČA" Institute of Nuclear Sciences - National Institute of the Republic of Serbia, University of Belgrade, 11001 Belgrade, Serbia
| | - Laurent Nahon
- Synchrotron SOLEIL, l'Orme des Merisiers, Saint Aubin BP 48, 91192 Cedex, Gif sur Yvette, France
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8
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Signorell R. Electron Scattering in Liquid Water and Amorphous Ice: A Striking Resemblance. PHYSICAL REVIEW LETTERS 2020; 124:205501. [PMID: 32501058 DOI: 10.1103/physrevlett.124.205501] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 04/29/2020] [Indexed: 05/25/2023]
Abstract
The lack of accurate low-energy electron scattering cross sections for liquid water is a substantial source of uncertainty in the modeling of radiation chemistry and biology. The use of existing amorphous ice scattering cross sections for the lack of liquid data has been discussed controversially for decades. Here, we compare experimental photoemission data of liquid water with corresponding predictions using amorphous ice cross sections, with the aim of resolving the debate regarding the difference of electron scattering in liquid water and amorphous ice. We find very similar scattering properties in the liquid and the ice for electron kinetic energies up to a few hundred electron volts. The scattering cross sections recommended here for liquid water are an extension of the amorphous ice cross sections. Within the framework of currently available experimental data, our work answers one of the most debated questions regarding electron scattering in liquid water.
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Affiliation(s)
- Ruth Signorell
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland
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9
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Abstract
Intriguing properties of photoemission from free, unsupported particles and droplets were predicted nearly 50 years ago, though experiments were a technical challenge. The last few decades have seen a surge of research in the field, due to advances in aerosol technology (generation, characterization, and transfer into vacuum), the development of photoelectron imaging spectrometers, and advances in vacuum ultraviolet and ultrafast light sources. Particles and droplets offer several advantages for photoemission studies. For example, photoemission spectra are dependent on the particle's size, shape, and composition, providing a wealth of information that allows for the retrieval of genuine electronic properties of condensed phase. In this review, with a focus on submicrometer-sized, dielectric particles and droplets, we explain the utility of photoemission from such systems, summarize several applications from the literature, and present some thoughts on future research directions.
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Affiliation(s)
- Loren Ban
- Department of Chemistry and Applied Biosciences, ETH Zürich, 8093 Zürich, Switzerland;
| | - Bruce L Yoder
- Department of Chemistry and Applied Biosciences, ETH Zürich, 8093 Zürich, Switzerland;
| | - Ruth Signorell
- Department of Chemistry and Applied Biosciences, ETH Zürich, 8093 Zürich, Switzerland;
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10
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Signorell R. Can Current Experimental Data Exclude Non-Gaussian Genuine Band Shapes in Ultraviolet Photoelectron Spectra of the Hydrated Electron? J Phys Chem Lett 2020; 11:1516-1519. [PMID: 32075380 PMCID: PMC7037147 DOI: 10.1021/acs.jpclett.0c00238] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Two recent articles present results that allegedly exclude a possible multimodal distribution of the hydrated electron in ultraviolet photoelectron spectra. The first article bases its conclusion on the assumption that the non-Gaussian genuine band shape previously retrieved for the solvated electron in liquid water is an artifact arising from insufficient electron scattering cross sections used in the retrieval. The second article excludes a multimodal band shape based on a photoelectron spectrum of the solvated electron in water clusters recorded at a single ultraviolet photon energy, and it further assumes that cluster results are transferable to the liquid without further justification. Here, we show that based on current data multimodal distributions cannot be unambiguously excluded. Furthermore, the transferability of cluster results to the liquid can be neither justified nor refuted on the basis of currently available experimental ultraviolet photoelectron spectra.
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