H(D)-atom yields in the quenching of Xe(6s[3∕2]1) by methane, ethane, ethene, ethyne, and their deuterated isotopologues

The Journal of Chemical Physics

2007

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The production yields of H(D) atoms in the reactions of N(2)(A (3)Sigma(u) (+)) with C(2)H(2), C(2)H(4), and their deuterated variants were determined. N(2)(A (3)Sigma(u) (+)) was produced by excitation transfer between Xe(6s[32](1)) and ground-state N(2) followed by collisional relaxation. Xe(6s[32](1)) was produced by two-photon laser excitation of Xe(6p[12](0)) followed by concomitant amplified spontaneous emission. H(D) atoms were detected by using vacuum-ultraviolet laser-induced fluorescence (LIF). The H(D)-atom yields were evaluated from the LIF intensities and the overall rate constants for the quenching, which were determined from the temporal profiles of the NO tracer emission. The absolute yields were evaluated by assuming that the yield for NH(3)(ND(3)) is 0.9. Although no HD isotope effects were observed in the overall rate constants, there were isotope effects in the H(D)-atom yields. The H-atom yields for C(2)H(2) and C(2)H(4) were 0.52 and 0.30, respectively, while the D-atom yields for C(2)D(2) and C(2)D(4) were 0.33 and 0.13, respectively. The presence of isotope effects in yields suggests that H(2)(D(2)) molecular elimination processes are competing and that molecular elimination is more dominant in deuterated species than in hydrides.

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: B Quantum Yields For the Production H"d… Atomsmentioning

confidence: 99%

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Production yields of H(D) atoms in the reactions of N2(AΣu+3) with C2H2, C2H4, and their deuterated variants

The Journal of Chemical Physics

2007

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“…The absolute densities of H atoms were measured by a vacuum-ultraviolet (vuv) laser absorption technique at 121.6 nm in the above study. Many spectroscopic techniques can detect H atoms in the gas phase, including vuv absorption spectroscopy, vuv laser induced fluorescence, two-photon laser induced fluorescence, resonance-enhanced multiphoton ionization and electron spin resonance [5,[35][36][37][38][39][40][41][42].…”

Section: Coating Techniques Of the Chamber Walls And The H-atom Densimentioning

confidence: 99%

Future prospect of remote Cat-CVD on the basis of the production, transportation and detection of H atoms

Matsumura

2008

Thin Solid Films

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The future prospect of remote Cat-CVD, in which the decomposition and the deposition chambers are separated, is discussed on the basis of the absolute density measurements of H atoms. It is now well recognized that uniform deposition is possible on a large area without plasma damages by Cat-CVD. However, we may not overlook the demerits in Cat-CVD. One of the demerits is the poisoning of the catalyzer surfaces by the material gases, both temporary and permanent. One technique to overcome this problem is remote Cat-CVD. The question is how to separate the decomposition and deposition areas. If the separation is not enough, there should be back diffusion of the material gases, which will poison the catalyzers. If the separation is too tight, radicals may not effuse out from the decomposition chamber. These problems are discussed and it is shown that SiO 2 coating to reduce the radical recombination rates on walls is promising. The possibility of the polytetrafluoroethene coating by Cat-CVD is also discussed.

Production and detection of reducing and oxidizing radicals in the catalytic decomposition of H2∕O2 mixtures on heated tungsten surfaces

Journal of Applied Physics

Moridera

2008

H atoms, O atoms, and OH radicals were identified in the catalytic decomposition of H2∕O2 mixtures on heated polycrystalline tungsten surfaces. In order to suppress the oxidization of the tungsten catalyzer surfaces, the H2∕O2 pressure ratio was kept more than 83, while the catalyzer temperature was kept below 2000K. The absolute density of H atoms was determined by a vacuum-ultraviolet laser absorption technique, while one-photon and two-photon laser-induced fluorescence techniques were employed to extend the dynamic range. Since the O-atom density was much smaller, only a vacuum-ultraviolet laser-induced fluorescence technique could be used for the detection. The absolute density could be estimated by comparing the induced fluorescence intensity with that for H atoms. OH radicals could be identified by a laser-induced fluorescence technique in the ultraviolet region. The absolute density was determined by comparing the induced fluorescence intensity with that of Rayleigh scattering caused by Ar. The H-atom density decreased with the increase in the O2 partial pressure stepwisely. The O-atom density increased with the O2 partial pressure monotonously, but the increase was rather slow at low O2 pressures. The OH-radical density showed saturation against the O2 partial pressure. These results can be explained by the change in the coverage conditions of the catalyzer surfaces.