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Christof Bartels - One of the best experts on this subject based on the ideXlab platform.
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Electron Hole Pair mediated vibrational excitation in co scattering from au 111 incidence energy and surface temperature dependence
Journal of Chemical Physics, 2014Co-Authors: Pranav R Shirhatti, Jorn Werdecker, Kai Golibrzuch, Alec M Wodtke, Christof BartelsAbstract:We investigated the translational incidence energy (Ei) and surface temperature (Ts) dependence of CO vibrational excitation upon scattering from a clean Au(111) surface. We report absolute v = 0 → 1 excitation probabilities for Ei between 0.16 and 0.84 eV and Ts between 473 and 973 K. This is now only the second collision system where such comprehensive measurements are available – the first is NO on Au(111). For CO on Au(111), vibrational excitation occurs via direct inelastic scattering through Electron Hole Pair mediated energy transfer – it is enhanced by incidence translation and the Electronically non-adiabatic coupling is about 5 times weaker than in NO scattering from Au(111). Vibrational excitation via the trapping desorption channel dominates at Ei = 0.16 eV and quickly disappears at higher Ei.We investigated the translational incidence energy (Ei) and surface temperature (Ts) dependence of CO vibrational excitation upon scattering from a clean Au(111) surface. We report absolute v = 0 → 1 excitation probabilities for Ei between 0.16 and 0.84 eV and Ts between 473 and 973 K. This is now only the second collision system where such comprehensive measurements are available – the first is NO on Au(111). For CO on Au(111), vibrational excitation occurs via direct inelastic scattering through Electron Hole Pair mediated energy transfer – it is enhanced by incidence translation and the Electronically non-adiabatic coupling is about 5 times weaker than in NO scattering from Au(111). Vibrational excitation via the trapping desorption channel dominates at Ei = 0.16 eV and quickly disappears at higher Ei.
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Electron Hole Pair mediated vibrational excitation in co scattering from au 111 incidence energy and surface temperature dependence
Journal of Chemical Physics, 2014Co-Authors: Pranav R Shirhatti, Jorn Werdecker, Kai Golibrzuch, Alec M Wodtke, Christof BartelsAbstract:We investigated the translational incidence energy (Ei) and surface temperature (Ts) dependence of CO vibrational excitation upon scattering from a clean Au(111) surface. We report absolute v = 0 → 1 excitation probabilities for Ei between 0.16 and 0.84 eV and Ts between 473 and 973 K. This is now only the second collision system where such comprehensive measurements are available – the first is NO on Au(111). For CO on Au(111), vibrational excitation occurs via direct inelastic scattering through Electron Hole Pair mediated energy transfer – it is enhanced by incidence translation and the Electronically non-adiabatic coupling is about 5 times weaker than in NO scattering from Au(111). Vibrational excitation via the trapping desorption channel dominates at Ei = 0.16 eV and quickly disappears at higher Ei.
Claude Bremard - One of the best experts on this subject based on the ideXlab platform.
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long lived Electron Hole Pair formation through photoionization of diphenylacetylene occluded in medium pores of aluminum rich m6 6zsm 5 zeolite m li na k rb cs influence of the counterbalancing cations on the recombination rate
Journal of Photochemistry and Photobiology A-chemistry, 2009Co-Authors: Fatima Belhadj, Alain Moissette, Claude BremardAbstract:Abstract Diffuse reflectance UV–vis and Raman spectroscopies show complete sorption of neutral diphenylacetylene (DPA) in the void space of M6.6ZSM-5 zeolites (M = Li+, Na+, K+, Rb+, Cs+) after several months of exposure of solid DPA to empty zeolite at room temperature. After a long organization period, the laser photolysis of DPA occluded in M6.6ZSM-5 generates long-lived DPA + radical cation as primary phenomenon. Charge recombination occurs mainly through Electron transfer and DPA@M6.6ZSM-5 − + Electron–Hole Pair formation. This subsequent Electron transfer takes place between the Electron deficient radical cation DPA + and the Electron donor oxygen atom of zeolite framework. The multivariate curve resolution analysis of the DRUVv spectra recorded during the reaction sequence including charge separation, Electron transfer and charge recombination provide the specific absorption spectra and respective spectral concentrations of all species as function of time. The DRUVv spectrum assigned to the long-lived DPA@M6.6ZSM-5 − + Electron–Hole Pair exhibits broad bands between 450 and 550 nm. The Electron–Hole Pair recombination depends on M+ and appears to be in relation with the Electron donor properties of the framework. The charge recombination rate decreases in the order Cs+ > Rb+ ∼ K+ > Na+ > Li+. The Electron–Hole Pair lifetime exceeds several hours at room temperature. The stabilization of DPA +-Electron Pair and DPA@M6.6ZSM-5 − + Electron–Hole Pair depends on the combined effects of confinement which dramatically reduces the DPA mobility in the zeolite void space and on the intrazeolithe electrostatic field of DPA@MnZSM-5 (M = Li+, Na+, K+, Rb+, Cs+).
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kinetics and characterization of photoinduced long lived Electron Hole Pair of p terphenyl occluded in zsm 5 zeolites effects of aluminium content and extraframework cation
Physical Chemistry Chemical Physics, 2009Co-Authors: Alain Moissette, Fatima Belhadj, Claude Bremard, Hervé VezinAbstract:Diffuse reflectance UV-visible in combination with FT-Raman spectroscopies demonstrate the total incorporation without any solvent of p-terphenyl (p-TP) as an intact molecule in the medium size channel of non-acidic MnZSM-5 (M = Li+, Na+, K+, Rb+, Cs+ and n = 0, 3.4, 6.6) zeolites. The combined effects of confinement and electrostatic field induced by alkaline ions in the MnZSM-5 zeolites lead only to weak conformational changes in the occluded p-TP after very long organization periods. The interaction between the counterbalancing cation and p-TP occurs through one phenyl group facially coordinated to the cation near the O atoms binding Al atoms. The laser UV photolysis of p-terphenyl occluded as intact molecules in non-acidic MnZSM-5 zeolites generates long-lived charge separated states. The photoionization induces a p-TP˙+–Electron Pair as a primary phenomenon. The recombination of the p-TP˙+@MnZSM-5˙− radical cation moiety occurs mainly through unusual Electron abstraction from the zeolite framework and p-TP@MnZSM-5˙−˙+ Electron–Hole Pair formation which exceeds several days at room temperature in Li6.6ZSM-5. The very long-lived radical Pairs are characterized by conventional DRUVv, FT-Raman and CW-EPR spectroscopy. Two-dimensional hyperfine sublevel correlation (2D-HYSCORE) experiments reveal the structural surroundings of the unPaired Electrons through the proper assignment of unPaired Electron couplings. The subsequent Hole transfer from the radical cation of the channels as well as the final Electron–Hole Pair recombination appear to be largely controlled by the aluminium content, the size of the extra framework cation and the associated local electrostatic field. The effects of the counterbalancing cations have been investigated and because the zeolite Electron affinity increases on going from Li+ to Cs+, the Electron transfer rates increase according to the following order Li+ < Na+ < K+ < Rb+ < Cs+.
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kinetics of Electron Hole Pair trapping via photoionization of biphenyl occluded in aluminium rich zsm 5 zeolites effects of extra framework cations
Physical Chemistry Chemical Physics, 2004Co-Authors: Isabelle Gener, Alain Moissette, Claude BremardAbstract:The effects of the extraframework cations M+ = Li+, Na+, K+, Rb+, Cs+ of aluminium rich M6.6ZSM-5 zeolites on the long-lived photoproducts of occluded biphenyl (BP) have been investigated by conventional diffuse reflectance UV-visible (DRUVv) absorption and continuous wave Electron paramagnetic resonance (CW-EPR). Many DRUVv and EPR spectra were recorded over two days after the UV laser photoionization (248 nm, 15 s, 30 mW cm−2) of dehydrated M6.6(AlO2)6.6(SiO2)89.4 samples loaded with 1 BP per unit cell. The application of EPR measurements provided evidence of durable BP˙+-Electron moiety through well resolved seven line signal (BP˙+) superimposed on a broad overlapping feature (trapped Electron). The EPR spectra recorded during the development of the irradiated samples at room temperature indicated the BP˙+ disappearance and the persistence of broad signal. These persistent structureless signals were assigned to very long-lived Electron–Hole Pairs. The application of the SIMPLISMA approach to DRUVv data sets recorded after the photolysis resolved two pure absorption spectra assigned to BP˙+ and Electron–Hole Pairs (420–500 nm) for all the irradiated samples. All the decays of corresponding concentrations were found to fit accurately a model of first order dispersed heterogeneous kinetics. The BP˙+ disappearance rate constants were found to increase with larger alkali metal cations (Li+ ∼ Na+ < K+ ∼ Rb+ ≪ Cs+) and correlated to the Electron-donating ability of the framework. The Electron abstraction by BP˙+ did not induce direct charge recombination but generated persistent Electron–Hole Pair over at most 1 h (Li+) and at least 1 min (Cs+). The Electron–Hole Pair recombination went to completion over more than two days (M = Li+) and less than 1 h (M = K+). The recombination rate was found to be in relation with the Electron donor properties of framework but probably involved other parameters.
Wolfgang Windl - One of the best experts on this subject based on the ideXlab platform.
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Electron Hole Pair generation in sic high temperature alpha particle detectors
Applied Physics Letters, 2013Co-Authors: Timothy R Garcia, Ashutosh Kumar, Benjamin Reinke, Thomas E Blue, Wolfgang WindlAbstract:We demonstrate alpha-particle detection in an n-type 4H-SiC Schottky diode detector up to a temperature of 500 °C using an Am-241 disc source. The measured spectra were used to calculate the Electron-Hole Pair creation energy in 4H-SiC and its non-bandgap contribution, which are both found to decrease with increasing temperature. The full width at half maximum (FWHM) of the measured alpha-energy peaks was found to increase exponentially with temperature due to an exponential increase of leakage current. For our measurement system, above 300 °C, where the leakage current was 10−6 A, this increase exceeded the FWHM at room temperature.
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Electron Hole Pair generation in sic high temperature alpha particle detectors
arXiv: Instrumentation and Detectors, 2013Co-Authors: Timothy R Garcia, Ashutosh Kumar, Benjamin Reinke, Thomas E Blue, Wolfgang WindlAbstract:We demonstrate alpha-particle detection in an n-type 4H-SiC Schottky diode detector up to an unprecedented temperature of 500 °C using an Am-241 disc source. The measured spectra were used to calculate the Electron-Hole Pair creation energy in 4H-SiC and its non-bandgap contribution, which are both found to decrease with increasing temperature. The full width at half maximum (FWHM) of the measured alpha-energy peaks was found to increase exponentially with temperature due to an exponential increase of leakage current. For our measurement system, above 300 °C, where the leakage current was 10-6 A, this increase exceeded the FWHM at room temperature.
Maite Alducin - One of the best experts on this subject based on the ideXlab platform.
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Electron Hole Pair effects in methane dissociative chemisorption on ni 111
Journal of Chemical Physics, 2016Co-Authors: Maite Alducin, Inaki J JuaristiAbstract:The dissociative chemisorption of methane on metal surfaces has attracted much attention in recent years as a prototype of gas-surface reactions in understanding the mode specific and bond selective chemistry. In this work, we systematically investigate the influence of Electron-Hole Pair excitations on the dissociative chemisorption of CH4/CH3D/CHD3 on Ni(111). The energy dissipation induced by surface Electron-Hole Pair excitations is modeled as a friction force introduced in the generalized Langevin equation, in which the independent atomic friction coefficients are determined within the local-density friction approximation. Quasi-classical trajectory calculations for CH4/CH3D/CHD3 have been carried out on a recently developed twelve-dimensional potential energy surface. Comparing the dissociation probabilities obtained with and without friction, our results clearly indicate that the Electron-Hole Pair effects are generally small, both on absolute reactivity of each vibrational state and on the mode specificity and bond selectivity. Given similar observations in both water and methane dissociation processes, we conclude that Electron-Hole Pair excitations would not play an important role as long as the reaction is direct and the interaction time between the molecule and metal Electrons is relatively short.
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Electron Hole Pair effects in polyatomic dissociative chemisorption water on ni 111
Journal of Physical Chemistry Letters, 2016Co-Authors: Bin Jiang, Maite AlducinAbstract:The influence of Electron–Hole Pairs in dissociative chemisorption of a polyatomic molecule (water) on metal surfaces is assessed for the first time using a friction approach. The atomic local density dependent friction coefficients computed based on a free Electron gas embedding model are employed in classical molecular dynamics simulations of the water dissociation dynamics on rigid Ni(111) using a recently developed nine dimensional interaction potential energy surface for the system. The results indicate that nonadiabatic effects are relatively small and they do not qualitatively alter the mode specificity in the dissociation.
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role of Electron Hole Pair excitations in the dissociative adsorption of diatomic molecules on metal surfaces
Physical Review Letters, 2008Co-Authors: Maite Alducin, J I Juaristi, Diez R Muino, H F Busnengo, A SalinAbstract:We quantitatively evaluate the contribution of Electron-Hole Pair excitations to the reactive dynamics of H2 on Cu(110) and N2 on W(110), including the six dimensionality of the process in the entire calculation. The interaction energy between molecule and surface is represented by an ab initio six-dimensional potential energy surface. Electron friction coefficients are calculated with density functional theory in a local density approximation. Contrary to previous claims, only minor differences between the adiabatic and nonadiabatic results for dissociative adsorption are found. Our calculations demonstrate the validity of the adiabatic approximation to analyze adsorption dynamics in these two representative systems.
Pranav R Shirhatti - One of the best experts on this subject based on the ideXlab platform.
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Electron Hole Pair mediated vibrational excitation in co scattering from au 111 incidence energy and surface temperature dependence
Journal of Chemical Physics, 2014Co-Authors: Pranav R Shirhatti, Jorn Werdecker, Kai Golibrzuch, Alec M Wodtke, Christof BartelsAbstract:We investigated the translational incidence energy (Ei) and surface temperature (Ts) dependence of CO vibrational excitation upon scattering from a clean Au(111) surface. We report absolute v = 0 → 1 excitation probabilities for Ei between 0.16 and 0.84 eV and Ts between 473 and 973 K. This is now only the second collision system where such comprehensive measurements are available – the first is NO on Au(111). For CO on Au(111), vibrational excitation occurs via direct inelastic scattering through Electron Hole Pair mediated energy transfer – it is enhanced by incidence translation and the Electronically non-adiabatic coupling is about 5 times weaker than in NO scattering from Au(111). Vibrational excitation via the trapping desorption channel dominates at Ei = 0.16 eV and quickly disappears at higher Ei.We investigated the translational incidence energy (Ei) and surface temperature (Ts) dependence of CO vibrational excitation upon scattering from a clean Au(111) surface. We report absolute v = 0 → 1 excitation probabilities for Ei between 0.16 and 0.84 eV and Ts between 473 and 973 K. This is now only the second collision system where such comprehensive measurements are available – the first is NO on Au(111). For CO on Au(111), vibrational excitation occurs via direct inelastic scattering through Electron Hole Pair mediated energy transfer – it is enhanced by incidence translation and the Electronically non-adiabatic coupling is about 5 times weaker than in NO scattering from Au(111). Vibrational excitation via the trapping desorption channel dominates at Ei = 0.16 eV and quickly disappears at higher Ei.
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Electron Hole Pair mediated vibrational excitation in co scattering from au 111 incidence energy and surface temperature dependence
Journal of Chemical Physics, 2014Co-Authors: Pranav R Shirhatti, Jorn Werdecker, Kai Golibrzuch, Alec M Wodtke, Christof BartelsAbstract:We investigated the translational incidence energy (Ei) and surface temperature (Ts) dependence of CO vibrational excitation upon scattering from a clean Au(111) surface. We report absolute v = 0 → 1 excitation probabilities for Ei between 0.16 and 0.84 eV and Ts between 473 and 973 K. This is now only the second collision system where such comprehensive measurements are available – the first is NO on Au(111). For CO on Au(111), vibrational excitation occurs via direct inelastic scattering through Electron Hole Pair mediated energy transfer – it is enhanced by incidence translation and the Electronically non-adiabatic coupling is about 5 times weaker than in NO scattering from Au(111). Vibrational excitation via the trapping desorption channel dominates at Ei = 0.16 eV and quickly disappears at higher Ei.