On obtaining surface time profiles from pulsed molecular beam scattering time-of-flight measurements

Brier, P.N.; Fletcher, J.; Gorry, P.A.

doi:10.1016/0039-6028(96)00718-2

Cited by 4 publications

(3 citation statements)

References 13 publications

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“…For the low-energy beam, we can neglect impulsive scattering such that the entire TOF profile consists of a series of time-shifted Maxwell−Boltzmann distributions weighted by the probability, p des ( t s ), that molecules in the incident gas pulse desorb from the surface at the time t s : where N MB is a Maxwell−Boltzmann distribution at the temperature of the surface and t s is the residence time of the molecules on the surface. ,,, We found that the TOF data are best described by a desorption probability function, p des ( t s ), of the form: The parameters A and B and time constants τ 1 and τ 2 were found using a nonlinear least-squares procedure . The desorption probability curves that provide the best fits to the N ( t ) data (see Figure ) are plotted in Figure .…”

Section: Resultsmentioning

confidence: 97%

Scattering, Accommodation, and Trapping of HCl in Collisions with a Hydroxylated Self-Assembled Monolayer

2005

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Time-of-flight molecular beam scattering techniques are used to explore the energy exchange, thermal accommodation, and residence time of HCl in collisions with an OH-terminated self-assembled monolayer. The monolayer, consisting of 16-mercapto-1-hexadecanol (HS(CH(2))(16)OH) self-assembled on gold, provides a well-characterized surface containing hydroxyl groups located at the gas-solid interface. Upon colliding with the hydroxylated surface, the gas-phase HCl is found to follow one of three pathways: direct impulsive scattering, thermal accommodation followed by prompt desorption, and temporary trapping through HO--- HCl hydrogen bond formation. For an incident energy of 85 kJ/mol, the HCl transfers the majority, >80%, of its translational energy to the surface. The extensive energy exchange facilitates thermalization, leading to very large accommodation probabilities on the surface. Under the experimental conditions used in this work, over 75% of the HCl approaches thermal equilibrium with the surface before desorption and, for a 6 kJ/mol HCl beam, nearly 100% of the molecules that recoil from the surface can be described by a thermal distribution at the temperature of the surface. For the molecules that reach thermal equilibrium with the surface prior to desorption, a significant fraction appear to form hydrogen bonds with surface hydroxyl groups. The adsorption energy, determined by measuring the HCl residence time as a function of surface temperature, is 24 +/- 2 kJ/mol.

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Section: Resultsmentioning

confidence: 97%

Scattering, Accommodation, and Trapping of HCl in Collisions with a Hydroxylated Self-Assembled Monolayer

2005

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“…Given the noise in the FTIR measurements, direct deconvolution is not practical in this case. A robust numerical procedure is to use a model function for NO resp (DED) and to perform the integration in Equation (10) numerically 12. The data fitting is carried out in two stages.…”

Section: Resultsmentioning

confidence: 99%

Adaptive Control for NO_x Removal in Non‐Thermal Plasma Processing

Gorry¹,

Whitehead²,

Wu³

2007

Plasma Processes & Polymers

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This paper presents results on NOx removal using a dielectric packed‐bed plasma reactor where the reactor energy is varied in real time to optimise NOx removal. An automated system has been developed using computer‐control with an industry standard software package, a multifunction DAQ card, on‐line fast FTIR spectroscopy and adaptive PID algorithms. The automatic control system has demonstrated real‐time control of plasma conditions which minimises the input energy for NO conversion for a range of input NO concentrations. The dependence of [NO]out on deposited energy density has been used to create a multidimensional response surface for NO destruction. This, in turn, has been used to create a fully validated process control model of the entire reactor‐FTIR‐adaptive PID system.

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“…A detailed description of the analysis procedures for obtaining from the measured T (t) has been given elsewhere. 43 The T s (t) most robust process is to supply a model form for the surface time proÐle and to perform the convolution integration T s (t) numerically to obtain T (t)Èwhich is then compared with the measured TOF. The shape of is adjusted to obtain the T s (t) best agreement.…”

Section: Gacl and Tof Distributions Asmentioning

confidence: 99%

Reactive scattering study of etching dynamics: HCl on GaAs(100)

Essex-Lopresti

Jia

Munro

et al. 2000

Phys. Chem. Chem. Phys.

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Pulsed supersonic molecular beam scattering has been used to study the inelastic scattering, trapping ] desorption and reactive channels for the HCl ] GaAs(100) thermal etching reactions. Temperature proÐles of the reaction products GaCl, and Ga are reported in the range 600 to 883 K. Angular and As 2 time-of-Ñight (TOF) distributions of inelastically scattered and trapped ] desorbed HCl are also reported. Angular distribution of all reaction products are described by a cosn (h) form with 0.95 O n O 1.4. The TOF distribution of GaCl reveals rapid production but with measurable time delay (50 lsÈ10 ms). The signals As 2 are e †ectively demodulated and correspond to delayed production on the surface with a time constant [1 s. A kinetic model initially proposed by Bent and colleagues (C.

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On obtaining surface time profiles from pulsed molecular beam scattering time-of-flight measurements

Cited by 4 publications

References 13 publications

Scattering, Accommodation, and Trapping of HCl in Collisions with a Hydroxylated Self-Assembled Monolayer

Scattering, Accommodation, and Trapping of HCl in Collisions with a Hydroxylated Self-Assembled Monolayer

Adaptive Control for NO_x Removal in Non‐Thermal Plasma Processing

Reactive scattering study of etching dynamics: HCl on GaAs(100)

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On obtaining surface time profiles from pulsed molecular beam scattering time-of-flight measurements

Cited by 4 publications

References 13 publications

Scattering, Accommodation, and Trapping of HCl in Collisions with a Hydroxylated Self-Assembled Monolayer

Scattering, Accommodation, and Trapping of HCl in Collisions with a Hydroxylated Self-Assembled Monolayer

Adaptive Control for NOx Removal in Non‐Thermal Plasma Processing

Reactive scattering study of etching dynamics: HCl on GaAs(100)

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Product

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Adaptive Control for NO_x Removal in Non‐Thermal Plasma Processing