Surface‐Aligned Femtochemistry: Real‐Time Dynamics of Photoinduced I<sub>2</sub> Formation from CD<sub>3</sub>I on MgO(100)

Vaida, Mihai E.; Bernhardt, Thorsten M.

doi:10.1002/cphc.200900920

Cited by 15 publications

(24 citation statements)

References 34 publications

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“…The alignment of the molecular C-I axis almost parallel to the surface normal has been confirmed in temperature programmed desorption measurements ͑see Fig. 40 The proposed adsorption geometry and the resulting molecular dynamics are also in accordance with the measured iodine transient signal ͓Fig. 28 and 8͒.…”

Section: Discussion Of the Photodissociation Dynamicssupporting

confidence: 77%

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Surface pump-probe femtosecond-laser mass spectrometry: Time-, mass-, and velocity-resolved detection of surface reaction dynamics

Vaida

Bernhardt

2010

Review of Scientific Instruments

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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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Section: Discussion Of the Photodissociation Dynamicssupporting

confidence: 77%

“…8,9,34,40,41 Future research in our laboratory will be directed along these lines with a focus on the femtochemistry of bimolecular surface reactions. 8,9,34,40,41 Future research in our laboratory will be directed along these lines with a focus on the femtochemistry of bimolecular surface reactions.…”

Section: Discussionmentioning

confidence: 99%

Surface pump-probe femtosecond-laser mass spectrometry: Time-, mass-, and velocity-resolved detection of surface reaction dynamics

Vaida

Bernhardt

2010

Review of Scientific Instruments

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“…The CD 3 + transient signal consists of a peak structure with a maximum at 50 fs. The interpretation of this transient is based on earlier experiments with methyl iodide on an insulating magnesia surface and on the power dependences of the pump and the probe laser, which support a single-photon excitation followed by a two-photon ionization [18,38–39]. …”

Section: Resultsmentioning

confidence: 94%

“…4 was obtained at this surface temperature and confirms that, under these multilayer conditions, the atomic and molecular iodine desorption from the iodine layer on the gold surface is suppressed because the iodine layer is completely covered by CD 3 I. In addition, when the sample was held at 100 K the methyl peak intensity was about 35 times higher than that at 150 K owing to the CD 3 I multilayer formation (note that at the chosen delay time of 130 fs no iodine atoms or I 2 molecules resulting from molecular CH 3 I photodissociation were detected with the employed probe laser beam [38]; the detected I-atoms and I 2 molecules in the mass spectrum must therefore originate from the iodine layer on the gold surface). On the modified gold surface (I/Au/Mo(100)) it was then possible to record the fs photodissociation dynamics of CD 3 I by monitoring the transient methyl cation signal intensity as a function of the pump–probe delay.…”

Section: Resultsmentioning

confidence: 99%

Femtosecond time-resolved photodissociation dynamics of methyl halide molecules on ultrathin gold films

Vaida¹,

Tchitnga²,

Bernhardt³

2011

Beilstein J. Nanotechnol.

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SummaryThe 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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“…The surface photoexcitation, the resonant multiphoton ionization detection scheme and the time‐resolved pump‐probe measurements were explained in greater detail, as were the photodissociation dynamics. In another publication in that same year, the group described the chemical details of the underlying photodissociation of the MgO‐CH 3 I/CD 3 I system leading to I 2 +• more thoroughly (Vaida & Bernhardt, ). A study also concentrating on these topics, but including additionally results for methyl bromide, was also published in the same year (Vaida et al, ).…”

Section: Photodissociationmentioning

confidence: 99%

Photoionization and photofragmentation in mass spectrometry with visible and UV lasers

Gunzer

Krüger

Grotemeyer

2018

Mass Spectrometry Reviews

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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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Surface‐Aligned Femtochemistry: Real‐Time Dynamics of Photoinduced I₂ Formation from CD₃I on MgO(100)

Cited by 15 publications

References 34 publications

Surface pump-probe femtosecond-laser mass spectrometry: Time-, mass-, and velocity-resolved detection of surface reaction dynamics

Surface pump-probe femtosecond-laser mass spectrometry: Time-, mass-, and velocity-resolved detection of surface reaction dynamics

Femtosecond time-resolved photodissociation dynamics of methyl halide molecules on ultrathin gold films

Photoionization and photofragmentation in mass spectrometry with visible and UV lasers

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Surface‐Aligned Femtochemistry: Real‐Time Dynamics of Photoinduced I2 Formation from CD3I on MgO(100)

Cited by 15 publications

References 34 publications

Surface pump-probe femtosecond-laser mass spectrometry: Time-, mass-, and velocity-resolved detection of surface reaction dynamics

Surface pump-probe femtosecond-laser mass spectrometry: Time-, mass-, and velocity-resolved detection of surface reaction dynamics

Femtosecond time-resolved photodissociation dynamics of methyl halide molecules on ultrathin gold films

Photoionization and photofragmentation in mass spectrometry with visible and UV lasers

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Surface‐Aligned Femtochemistry: Real‐Time Dynamics of Photoinduced I₂ Formation from CD₃I on MgO(100)