Dynamical parameters of desorbing molecules

Comşa, George; David, Rudolf

doi:10.1016/0167-5729(85)90009-3

Cited by 403 publications

(188 citation statements)

References 53 publications

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“…The translational energy can be used to judge the collimation angle of desorption components because it is peaked at this angle in the repulsive desorption. 4,38 Each velocity distribution of desorbing N 2 clearly shows the thermalized component in the NO + CO reaction above 550 K. Typical velocity distributions at T S = 550 K and P NO = P CO =5ϫ 10 −6 Torr are shown in Fig. 7.…”

Section: Velocity Distributionmentioning

confidence: 99%

“…The speed ratio is usually below unity for a hyperthermal component at around the collimation position. 38 A translational temperature of 3420 K corresponds to an energy of 0.59 eV, which is higher than the excitation energy of the molecular vibration of N 2 at the ground state, 0.28 eV. 39 Desorbing fast N 2 may involve vibrationally and/or rotationally excited molecules.…”

Section: -5mentioning

confidence: 99%

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Spatial distributions of desorbing products in steady-state NO and N2O reductions on Pd(110)

Matsushima

Shobatake

et al. 2006

The Journal of Chemical Physics

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The angular and velocity distributions of desorbing product N 2 were examined over the crystal azimuth in steady-state NO + CO and N 2 O + CO reactions on Pd͑110͒ by cross-correlation time-of-flight techniques. At surface temperatures below 600 K, N 2 desorption in both reactions splits into two directional lobes collimated along 41°-45°from the surface normal toward the ͓001͔ and ͓001͔ directions. Above 600 K, the normally directed N 2 desorption is enhanced in the NO reduction. Each product desorption component, as well as CO 2 , shows a fairly asymmetric distribution about its collimation axis. Two factors, i.e., the anisotropic site structures and the reactant orientation and movements, are operative to induce such asymmetry, depending on the product emission mechanism.

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Section: Velocity Distributionmentioning

confidence: 99%

Section: -5mentioning

confidence: 99%

Spatial distributions of desorbing products in steady-state NO and N2O reductions on Pd(110)

Matsushima

Shobatake

et al. 2006

The Journal of Chemical Physics

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“…This dependence indicates facile energy partitionings into the rotational, vibrational, and translational modes in different ways in a repulsive product desorption event. 4,34,41,42 AR product desorption will deliver more information when it can be performed at a level of state-selective product analysis in the course of catalyzed reactions. This next stage becomes important in improving the method because each energy state of desorbing products will show different surface structures.…”

Section: Discussion and Remarksmentioning

confidence: 99%

Internal-energy measurements of angle-resolved product CO2 in catalytic CO oxidation by means of infrared chemiluminescence

Yamanaka

Matsushima

2007

Review of Scientific Instruments

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Measurements of both vibrational and rotational energies of product CO 2 in CO oxidation on palladium surfaces have been successfully performed as a function of the desorption angle by means of infrared chemiluminescence. The remarkable angle dependences of both energies indicate facile energy partitioning in repulsive desorption and provide new dimensions in the study of surface reaction dynamics as well as additional insights into the product formation site. Details of the apparatus for energy analysis of angle-resolved products are described, especially on how to pick up extremely weak infrared emission signals.

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“…Note that the expression for the angular distribution contains the factor cos ⌰ f , which ensures that a complete accommodation of parallel momentum results in a cosine distribution. 43 This factor arises from the volume element for the scattered flux per unit area on the surface at the angle ⌰ f . 24 The angular distribution for the partially conserved parallel momentum is most simply given by the integral and the ͗E f ͘ (ϭ͗E trans ͒͘/E i distribution is given by an additional factor of E trans inside the integral in the numerator.…”

Section: ͑A8͒mentioning

confidence: 99%

Rotational excitation in scattering of hyperthermal NO from Pt(111)

Wiskerke

Taatjes

Kleyn

et al. 1995

The Journal of Chemical Physics

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Rotational distributions from NO-Pt͑111͒ scattering have been reported ͓Wiskerke et al., J. Chem. Phys. 102, 3835 ͑1995͔͒. At lower incoming energies ͑Ͻ1 eV͒ clear rotational rainbows are seen, but the distributions for higher energies approach Boltzmann distributions with apparent temperatures far exceeding the surface temperature. We compare here the NO-Pt͑111͒ scattering distributions to the predictions of a simple statistical model. The model assumes randomization of the available energy, subject to ͑partial͒ conservation of parallel linear momentum and angular momentum about the surface normal. Some characteristics of the rotational and angular distributions which arise from such a statistical energy repartitioning are discussed and compared to experimental results. It is seen that a combination of peaked angular distributions and Boltzmann-type rotational distributions independent of the scattering angle are reproduced by a simple statistical calculation with partial conservation of parallel linear momentum. For the NO-Pt͑111͒ system, it is shown that a complete description of the high-energy scattering requires specifically dynamical assumptions. The transition from ''dynamics'' to ''statistics'' most likely arises from a combination of increased averaging, resulting from a competition between scattering via different regions of the potential energy surface, and a weakening of the rainbow features, perhaps due to the onset of chattering collisions.

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Dynamical parameters of desorbing molecules

Cited by 403 publications

References 53 publications

Spatial distributions of desorbing products in steady-state NO and N2O reductions on Pd(110)

Spatial distributions of desorbing products in steady-state NO and N2O reductions on Pd(110)

Internal-energy measurements of angle-resolved product CO2 in catalytic CO oxidation by means of infrared chemiluminescence

Rotational excitation in scattering of hyperthermal NO from Pt(111)

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