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Pathan MAK, Gupta A, Vaida ME. Understanding the Effect of an Amorphous Surface on the Ultrafast Dynamics of a Heterogeneous Photoinduced Reaction: CD 3I Photoinduced Reaction on Amorphous Cerium Oxide Films. J Phys Chem Lett 2022; 13:9759-9765. [PMID: 36226789 DOI: 10.1021/acs.jpclett.2c02294] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
In this work, to understand how an amorphous surface influences the dynamics of surface photoinduced reactions, pump-probe spectroscopy in conjunction with mass spectrometry is employed to track the ultrafast evolution of intermediates and final products with time, mass, and energy resolution. As a model system, the photoinduced reaction of CD3I adsorbed on amorphous cerium oxide films is investigated. A fraction of the first intermediates produced on a freshly prepared surface is trapped to passivate the surface. After the A-band excitation, the minimum dissociation time of CD3I indicates that CD3I adsorption geometries with either CD3 or I facing the gas phase exist; however, the transient data suggest that most molecules are adsorbed with the I atom facing the surface. CD3 and I are consumed to form I2 and reform CD3I, which are produced at a steady rate only after the intermediates have lost the excess translational energy released from photodissociation.
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Affiliation(s)
- Md Afjal Khan Pathan
- Department of Physics, University of Central Florida, Orlando, Florida32816, United States
| | - Aakash Gupta
- Department of Physics, University of Central Florida, Orlando, Florida32816, United States
| | - Mihai E Vaida
- Department of Physics, University of Central Florida, Orlando, Florida32816, United States
- Renewable Energy and Chemical Transformations Cluster, University of Central Florida, Orlando, Florida32816, United States
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Vaida ME, Rawal TB, Bernhardt TM, Marsh BM, Rahman TS, Leone SR. Nonmetal-to-Metal Transition of Magnesia Supported Au Clusters Affects the Ultrafast Dissociation Dynamics of Adsorbed CH 3Br Molecules. J Phys Chem Lett 2022; 13:4747-4753. [PMID: 35612537 DOI: 10.1021/acs.jpclett.2c00968] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The detection of intermediate species and the correlation of their ultrafast dynamics with the morphology and electronic structure of a surface is crucial to fully understand and control heterogeneous photoinduced and photocatalytic reactions. In this work, the ultrafast photodissociation dynamics of CH3Br molecules adsorbed on variable-size Au clusters on MgO/Mo(100) is investigated by monitoring the CH3+ transient evolution using a pump-probe technique in conjunction with surface mass spectrometry. Furthermore, extreme-UV photoemission spectroscopy in combination with theoretical calculations is employed to study the electronic structure of the Au clusters on MgO/Mo(100). Changes in the ultrafast dynamics of the CH3+ fragment are correlated with the electronic structure of Au as it evolves from monomers to small nonmetallic clusters to larger nanoparticles with a metallic character. This work provides a new avenue to a detailed understanding of how surface-photoinduced chemical reactions are influenced by the composition and electronic structure of the surface.
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Affiliation(s)
- Mihai E Vaida
- Department of Physics, University of Central Florida, Orlando, Florida 32816, United States
- Renewable Energy and Chemical Transformations Cluster, University of Central Florida, Orlando, Florida 32816, United States
| | - Takat B Rawal
- Department of Physics, University of Central Florida, Orlando, Florida 32816, United States
| | - Thorsten M Bernhardt
- Institute of Surface Chemistry and Catalysis, University of Ulm, 89069 Ulm, Germany
| | - Brett M Marsh
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Talat S Rahman
- Department of Physics, University of Central Florida, Orlando, Florida 32816, United States
- Renewable Energy and Chemical Transformations Cluster, University of Central Florida, Orlando, Florida 32816, United States
| | - Stephen R Leone
- Department of Chemistry, University of California, Berkeley, California 94720, United States
- Department of Physics, University of California, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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Gunzer F, Krüger S, Grotemeyer J. Photoionization and photofragmentation in mass spectrometry with visible and UV lasers. MASS SPECTROMETRY REVIEWS 2019; 38:202-217. [PMID: 30300954 DOI: 10.1002/mas.21579] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Accepted: 08/29/2018] [Indexed: 06/08/2023]
Abstract
Ever since the introduction of laser technology to the field of mass spectrometry, several disciplines evolved providing solutions to challenging scientific and analytical tasks in research and industry. Among these are techniques involving multiphoton ionization such as Resonance-Enhanced Multiphoton Ionization (REMPI, R2PI) and Mass-Analyzed Threshold Ionization (MATI) spectroscopy, a variant of Zero Kinetic Energy (ZEKE) spectroscopy, that possess the ability to selectively ionize certain preselected compounds out of complex mixtures, for example, environmental matrices, with a high level of efficiency. Another key feature of multiphoton ionization techniques is the ability to control the degree of fragmentation, whereas soft ionization is most highly appreciated in most applications. In cases where rich fragmentation patterns are desired for diagnostic purposes, Photodissociation mass spectrometry (PD-MS) is applied successfully. PD-MS allows for the cleavage of selected chemical bonds. With the introduction of chromophoric labels in PD-MS, it became possible to target certain molecules or groups within a molecule. In this review article, an overview of the basic principles and experimental requirements of REMPI and MATI spectroscopy and PD mass spectrometry are given. By means of selected examples, the latest developments and application possibilities in this field over the past decade with special focus on the German research landscape are pointed out. © 2018 Wiley Periodicals, Inc. Mass Spec Rev 38: 202-217, 2019.
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Affiliation(s)
- Frank Gunzer
- Physics Department, German University in Cairo, New Cairo City, Cairo, Egypt
| | - Sascha Krüger
- Department for Laser Mass Spectrometry, Institute for Physical Chemistry, Christian-Albrecht-University Kiel, Max-Eyth-Strasse 1, 24118 Kiel, Germany
| | - Jürgen Grotemeyer
- Department for Laser Mass Spectrometry, Institute for Physical Chemistry, Christian-Albrecht-University Kiel, Max-Eyth-Strasse 1, 24118 Kiel, Germany
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Vaida ME, Bernhardt TM. Tuning the ultrafast photodissociation dynamics of CH 3 Br on ultrathin MgO films by reducing the layer thickness to the 2D limit. Chem Phys Lett 2017. [DOI: 10.1016/j.cplett.2017.09.019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Attar AR, Bhattacherjee A, Leone SR. Direct Observation of the Transition-State Region in the Photodissociation of CH3I by Femtosecond Extreme Ultraviolet Transient Absorption Spectroscopy. J Phys Chem Lett 2015; 6:5072-7. [PMID: 26636176 DOI: 10.1021/acs.jpclett.5b02489] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Femtosecond extreme ultraviolet (XUV) pulses produced by high harmonic generation are used to probe the transition-state region in the 266 nm photodissociation of CH3I by the real-time evolution of core-to-valence transitions near the iodine N-edge at 45-60 eV. During C-I bond breaking, new core-to-valence electronic states appear in the spectra, which decay concomitantly with the rise of the atomic iodine resonances of I((2)P3/2) and I*((2)P1/2). The short-lived features are assigned to repulsive valence-excited transition-state regions of (3)Q0 and (1)Q1, which can connect to transient core-excited states via promotion of 4d(I) core electrons. A simplified one-electron transition picture is described that accurately predicts the relative energies of the transient states observed. The transition-state resonances reach a maximum at ∼40 fs and decay to complete C-I dissociation in ∼90 fs, representing the shortest-lived chemical transition state observed by core-level, XUV, or X-ray spectroscopy.
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Affiliation(s)
- Andrew R Attar
- Department of Chemistry, University of California , Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - Aditi Bhattacherjee
- Department of Chemistry, University of California , Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - Stephen R Leone
- Department of Chemistry, University of California , Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
- Department of Physics, University of California , Berkeley, California 94720, United States
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Miller ER, Muirhead GD, Jensen ET. Mechanisms for the near-UV photodissociation of CH3I on D2O/Cu(110). J Chem Phys 2013; 138:084702. [DOI: 10.1063/1.4770225] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Vaida ME, Bernhardt TM. Surface-aligned femtochemistry: Photoinduced reaction dynamics of CH3I and CH3Br on MgO(100). Faraday Discuss 2012; 157:437-49; discussion 475-500. [DOI: 10.1039/c2fd20104f] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Vaida ME, Tchitnga R, Bernhardt TM. Femtosecond time-resolved photodissociation dynamics of methyl halide molecules on ultrathin gold films. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2011; 2:618-27. [PMID: 22003467 PMCID: PMC3190631 DOI: 10.3762/bjnano.2.65] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Accepted: 09/16/2011] [Indexed: 05/12/2023]
Abstract
The photodissociation of small organic molecules, namely methyl iodide, methyl bromide, and methyl chloride, adsorbed on a metal surface was investigated in real time by means of femtosecond-laser pump-probe mass spectrometry. A weakly interacting gold surface was employed as substrate because the intact adsorption of the methyl halide molecules was desired prior to photoexcitation. The gold surface was prepared as an ultrathin film on Mo(100). The molecular adsorption behavior was characterized by coverage dependent temperature programmed desorption spectroscopy. Submonolayer preparations were irradiated with UV light of 266 nm wavelength and the subsequently emerging methyl fragments were probed by photoionization and mass spectrometric detection. A strong dependence of the excitation mechanism and the light-induced dynamics on the type of molecule was observed. Possible photoexcitation mechanisms included direct photoexcitation to the dissociative A-band of the methyl halide molecules as well as the attachment of surface-emitted electrons with transient negative ion formation and subsequent molecular fragmentation. Both reaction pathways were energetically possible in the case of methyl iodide, yet, no methyl fragments were observed. As a likely explanation, the rapid quenching of the excited states prior to fragmentation is proposed. This quenching mechanism could be prevented by modification of the gold surface through pre-adsorption of iodine atoms. In contrast, the A-band of methyl bromide was not energetically directly accessible through 266 nm excitation. Nevertheless, the one-photon-induced dissociation was observed in the case of methyl bromide. This was interpreted as being due to a considerable energetic down-shift of the electronic A-band states of methyl bromide by about 1.5 eV through interaction with the gold substrate. Finally, for methyl chloride no photofragmentation could be detected at all.
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Affiliation(s)
- Mihai E Vaida
- Institute of Surface Chemistry and Catalysis, University of Ulm, Albert-Einstein-Allee 47, 89069 Ulm, Germany
| | - Robert Tchitnga
- Institute of Surface Chemistry and Catalysis, University of Ulm, Albert-Einstein-Allee 47, 89069 Ulm, Germany
| | - Thorsten M Bernhardt
- Institute of Surface Chemistry and Catalysis, University of Ulm, Albert-Einstein-Allee 47, 89069 Ulm, Germany
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Vaida ME, Bernhardt TM. Surface pump-probe femtosecond-laser mass spectrometry: time-, mass-, and velocity-resolved detection of surface reaction dynamics. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2010; 81:104103. [PMID: 21034102 DOI: 10.1063/1.3488098] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
A detailed account of the experimental methodology of surface pump-probe femtosecond-laser mass spectrometry is presented. This recently introduced technique enables the direct time-resolved investigation of surface reaction dynamics by monitoring the mass and the relative velocity of intermediates and products of a photoinduced surface reaction via multiphoton ionization. As a model system, the photodissociation dynamics of methyl iodide adsorbed at submonolayer coverage on magnesia ultrathin films is investigated. The magnesia surface preparation and characterization as well as the pulsed deposition of methyl iodide are described. The femtosecond-laser excitation (pump) and, in particular, the resonant multiphoton ionization surface detection (probe) schemas are discussed in detail. Results of pump-probe time-resolved methyl and iodine atom detection experiments are presented and the potential of this method for velocity-resolved photofragment analysis is evaluated.
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Affiliation(s)
- Mihai E Vaida
- Institute of Surface Chemistry and Catalysis, University of Ulm, Albert-Einstein-Allee 47, 89069 Ulm, Germany
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Vaida ME, Bernhardt TM. Surface-Aligned Femtochemistry: Real-Time Dynamics of Photoinduced I2Formation from CD3I on MgO(100). Chemphyschem 2010; 11:804-7. [DOI: 10.1002/cphc.200900920] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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