Three-dimensional velocity map imaging of KBr surface photochemistry

Koehler, Sven P. K.; Ji, Yuanyuan; Auerbach, Daniel J.; Wodtke, Alec M.

doi:10.1039/b909579a

Cited by 19 publications

(27 citation statements)

References 16 publications

(15 reference statements)

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“…13 For completeness, we give a brief description here with emphasis on changes from the previous setup and the features that are important for this work.…”

Section: Apparatusmentioning

confidence: 99%

“…In our earlier work, 13 we introduced CH 3 Br via an effusive beam along the z-axis of the apparatus. Here, we introduced CH 3 Br as background gas at a pressure of ϳ5 ϫ 10 −7 Torr.…”

Section: A Voltages For Velocity Map Imaging and Vmi Velocity Calibrmentioning

confidence: 99%

“…Despite these concerns, the results obtained with the "background gas approach" for obtaining the optimum value of V E were in good agreement with those obtained with the effusive molecular beam. 13 For future work, it could be desirable to find a way to introduce a molecular beam with the crystal in place. This might be accomplished, for example, by cutting a small hole in the center of the crystal and using this hole as the aperture for a molecular beam.…”

Section: A Voltages For Velocity Map Imaging and Vmi Velocity Calibrmentioning

confidence: 99%

“…The REMPI laser is focused by a 20 cm focal length lens, rather than the 38 cm lens used in our previous work. 13 We chose a shorter focal length lens to reduce the two-photon Rayleigh length; that is, the length of the detec-FIG. 1.…”

Section: Apparatusmentioning

confidence: 99%

“…[8][9][10][11][12] Recently, we demonstrated the use of VMI to measure three-dimensional velocity distributions of Br͑ 2 P 3/2 ͒ and Br͑ 2 P 1/2 ͒ atoms ͑which we hereafter refer to as Br and Br ‫ء‬ ͒ resulting from photodesorption from the surface of a KBr crystal. 13 We chose this system as a test case for the technique since it had been previously studied by other methods. 14,15 By using a combination of TOF and VMI techniques, we were able to obtain three-dimensional velocity map images of desorbing Br and Br ‫ء‬ , that is the desorption probability, P, as a function of three Cartesian components ͑v x , v y , and v z ͒ of the velocity vector, v ជ.…”

Section: Introductionmentioning

confidence: 99%

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Surface three-dimensional velocity map imaging: A new technique for the study of photodesorption dynamics

Koehler

Auerbach

et al. 2010

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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Validation of velocity map imaging conditions over larger areas Rev. Sci. Instrum. 84, 044101 (2013) The authors describe the application of a combination of velocity map imaging and time-of-flight ͑TOF͒ techniques to obtain three-dimensional velocity distributions for surface photodesorption. They have established a systematic alignment procedure to achieve correct and reproducible experimental conditions. It includes four steps: ͑1͒ optimization of the velocity map imaging ion optics' voltages to achieve optimum velocity map imaging conditions; ͑2͒ alignment of the surface normal with the symmetry axis ͑ion flight axis͒ of the ion optics; ͑3͒ determination of TOF distance between the surface and the ionizing laser beam; ͑4͒ alignment of the position of the ionizing laser beam with respect to the ion optics. They applied this set of alignment procedures and then measured Br͑ 2 P 3/2 ͒ ͑Br͒ and Br͑ 2 P 1/2 ͒ ͑Br ‫ء‬ ͒ atoms photodesorbing from a single crystal of KBr after exposure to 193 nm light. They analyzed the velocity flux and energy flux distributions for motion normal to the surface. The Br ‫ء‬ normal energy distribution shows two clearly resolved peaks at approximately 0.017 and 0.39 eV, respectively. The former is slightly faster than expected for thermal desorption at the surface temperature and the latter is hyperthermal. The Br normal energy distribution shows a single broad peak that is likely composed of two hyperthermal components. The capability that surface three-dimensional velocity map imaging provides for measuring state-specific velocity distributions in all three dimensions separately and simultaneously for the products of surface photodesorption or surface reactions holds great promise to contribute to our understanding of these processes.

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“…13 For completeness, we give a brief description here with emphasis on changes from the previous setup and the features that are important for this work.…”

Section: Apparatusmentioning

confidence: 99%

“…In our earlier work, 13 we introduced CH 3 Br via an effusive beam along the z-axis of the apparatus. Here, we introduced CH 3 Br as background gas at a pressure of ϳ5 ϫ 10 −7 Torr.…”

Section: A Voltages For Velocity Map Imaging and Vmi Velocity Calibrmentioning

confidence: 99%

Section: A Voltages For Velocity Map Imaging and Vmi Velocity Calibrmentioning

confidence: 99%

Section: Apparatusmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Surface three-dimensional velocity map imaging: A new technique for the study of photodesorption dynamics

Koehler

Auerbach

et al. 2010

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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Surface processes on KBr single crystals examined by thermostimulated exo-electron emission and desorption

et al. 2021

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Velocity-Selected Rotational State Distributions of Nitric Oxide Scattered off Graphene Revealed by Surface-Velocity Map Imaging

2023

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We report velocity-dependent internal energy distributions of nitric oxide molecules, NO, scattered off graphene supported on gold to further explore the dynamics of the collision process between NO radicals and graphene. These experiments were performed by directing a molecular beam of NO onto graphene in a surface-velocity map imaging setup, which allowed us to record internal energy distributions of the NO radicals as a function of their velocity. We do not observe bond formation but (1) major contributions from direct inelastic scattering and (2) a smaller trapping−desorption component where some physisorbed NO molecules have residence times on the order of microseconds. This is in agreement with our classical molecular dynamics simulations which also observe a small proportion of two-and multi-bounce collisions events but likewise a small proportion of NO radicals trapped at the surface for the entire length of the molecular dynamics simulations (a few picoseconds). Despite a collision energy of 0.31 eV, which would be sufficient to populate NO(v = 1), we do not detect vibrationally excited nitric oxide.

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Three-dimensional velocity map imaging of KBr surface photochemistry

Cited by 19 publications

References 16 publications

Surface three-dimensional velocity map imaging: A new technique for the study of photodesorption dynamics

Surface three-dimensional velocity map imaging: A new technique for the study of photodesorption dynamics

Surface processes on KBr single crystals examined by thermostimulated exo-electron emission and desorption

Velocity-Selected Rotational State Distributions of Nitric Oxide Scattered off Graphene Revealed by Surface-Velocity Map Imaging

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