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194 results on '"Davies, P.B."'

8. Infrared laser spectrum and structure of phosphoryl chloride (ClPO) formed at ambient temperature in the gas phase

Author

Bell, I.S., Hamilton, P.A., and Davies, P.B.

Subjects
Infrared spectroscopy -- Usage, Laser spectroscopy -- Usage, Chlorides -- Analysis, Chemicals, plastics and rubber industries
Abstract

The infrared spectrum of the transient molecule phosphoryl chloride (CIPO) was assessed in the gas phase at room temperature by applying infrared diode laser absorption spectroscopy around 8 microns. The molecule was produced in a flow system either by adding molecular chlorine to a mixture of white phosphorus vapor and oxygen or by reacting atomic oxygen with phosphorus trichloride vapor. The infrared spectrum comes from the P-O stretching fundamental of CIPO.

Published
1998

10. Infrared laser diagnostics in methane chemical-vapor-deposition plasmas

Author

Davies, P.B. and Martineau, P.M.

Subjects
Chemical vapor deposition -- Research, Laser plasmas -- Research, Physics
Abstract

Tunable diode laser spectroscopy, mass spectrometry and optical emission spectroscopy were used to investigate the reactive species concentrations in an radio frequency chemical vapor deposition reactor. The results showed that several types of reactive hydrogen species were present. However, there was no spatial variation in methyl radical concentration. The carbon film growth rate varied linearly with the CH3 concentration.

Published
1992

15. High-resolution laser spectroscopy of the nu6 fundamental band of jet-cooled C2F6

Author

Lorono, M., Henze, W., and Davies, P.B.

Subjects
Density functionals -- Usage, Ethanes -- Chemical properties, Laser spectroscopy -- Usage, Chemicals, plastics and rubber industries
Abstract

The nu6 parallel band of C2F6 is measured at high resolution by using diode laser absorption spectroscopy in a free jet expansion. A comparison of the rotational intensity distribution with simulated band profiles indicated a rotational temperature of between 2 and 3 K in the jet. The concluded value is independent of the electron diffraction structure.

Published
2000

21. Trace gas measurements using optically resonant cavities and quantum cascade lasers operating at room temperature

Author

Welzel, S., Lombardi, G., Davies, P.B., Engeln, R., Schram, D.C., and Ropcke, J.

Subjects
Infrared detectors -- Evaluation, Lasers -- Thermal properties, Lasers -- Electric properties, Spectrum analysis -- Usage, Laser, Physics
Abstract

The sensitivity limits of an entirely thermoelectrically (TE) cooled quantum cascade laser (QCL) system equipped with an 0.5 m long cavity having small sample volume of 0.3 l are examined. The studies have shown that the application of TE cooled pulsed QCLs for integrated cavity output spectroscopy and cavity ring-down spectroscopy (CRDS) is limited by the intrinsic frequency chirp of the laser.

Published
2008

25. Sum-frequency generation from thiophenol on silver in the mid and far-IR.

Author

Braun, R., Casson, B.D., Bain, C.D., van der Ham, E.W.M., Vrehen, Q.H.F., Eliel, E.R., Briggs, A.M., and Davies, P.B.

Subjects
THIOPHENES, MONOMOLECULAR films, FREQUENCY spectra
Abstract

Reports on the sum frequency spectra of a monolayer of thiophenol on silver in the mid and far-infrared. Use of the free electron laser to reach wavelengths up to 54 micrometer; Observation of molecular vibrations of thiophenol at wavelengths near ten micrometer; Variation of the appearance of different vibrational models in the spectra.

Published
1999
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28. Fundamental and Applied Studies of Molecular Plasmas Using Infrared Absorption Techniques

Author

Röpcke, J., Davies, P.B., van Helden, J.H., Hübner, M., Lang, N., Welzel, S., Bonitz, M., and al, et

Subjects
Absorption spectroscopy, Chemistry, Infrared, law, Analytical chemistry, Infrared spectroscopy, Plasma diagnostics, Nanotechnology, Thin film, Spectroscopy, Quantum cascade laser, Laser, law.invention
Abstract

Over the past few years mid infrared absorption spectroscopy (MIR-AS) over the region from 3 to 20 ?m has progressed considerably as a powerful diagnostic technique for in situ studies of the fundamental physics and chemistry of molecular plasmas. The increasing interest in processing plasmas containing hydrocarbons, fluorocarbons, nitrogen oxides and organo-silicon compounds has led to further applications of MIR-AS because most of these compounds and their decomposition products are infrared active. MIR-AS provides a means of determining the absolute concentrations of the ground states of stable and transient molecular species at time resolutions below a micro second, which is of particular importance for the investigation of reaction kinetics and dynamics. Information about gas temperature and population densities can also be derived from MIR-AS measurements. Since plasmas with molecular feed gases are used in many applications such as thin film deposition, semiconductor processing, surface activation and cleaning, and materials and waste treatment, this has stimulated the adaptation of MIR-AS techniques to industrial requirements including the development of new diagnostic equipment. The aim of the present chapter is fourfold: (i) to briefly summarize the basic principles of infrared absorption spectroscopy and related instrumentation, (ii) to report on recent achievements in our understanding of molecular phenomena in plasmas using different types of MIR-AS techniques, (iii) to describe examples of industrial process monitoring in the mid infrared and (iv) to discuss the potential of advanced instrumentation based on quantum cascade lasers (QCLs) for plasma diagnostics.

Published
2014

29. Diagnostic emission and absorption spectroscopy

Author

Roepcke, J., Rousseau, Antoine, Lavrov, B.P., Davies, P.B., Laboratoire de Physique des Plasmas (LPP), Université Paris-Sud - Paris 11 (UP11)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2012

32. Infrared absorption spectroscopic studies of the methyl and boron monoxide radical

Author

Stancu, Gabi-Daniel, Röpcke, Jürgen, Davies, P.B., LE PIOLET, DELPHINE, Laboratoire d'Énergétique Moléculaire et Macroscopique, Combustion (EM2C), and CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-Université Paris Saclay (COmUE)

Subjects
[SPI]Engineering Sciences [physics], [SPI] Engineering Sciences [physics], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2006

35. The Science Case for 4GLS

Author

Allan, R.J., Allen, M.P., Alexandrov, A.S., Ashfold, M.N.R., Atkinson, R., Avaldi, L., Bain, C.D., Bancroft, J., Barrett, S.D., Barron, L.D., Bayliss, S., Becker, U., Benning, L.G., Berrah, N., Binns, C., Bisby, R.H., Bizau, J.M., Blake, R.J., Bowler, M.A., Bowyer, J., Brettle, J., Briggs, D., Brown, L.M., Brown, W.A., Burke, P.G., Cacho, C., Carter, R., Catlow, R., Cernik, R.J., Chesters, M., Clark, S.A., Clarke, D.T., Clarke, J.A., Codling, K., Cogdell, R., Connaughton, D., Connerade, J.P., Costello, J.T., Crapper, M.D., Creaser, C., Currell, F.J., Davies, P.B., de Jong, M., Dessent, C., Dhanak, V.R., Dobson, D.M., Dobson, P.J., Doig, A.J., Donovan, R.J., Dumas, P., Dunn, K., Dutuit, O., Dyke, J.M., Eastham, D.A., Egdell, R.G., Eland, J.H.D., Emerson, D.R., Eriksson, M., Erman, P., Evans, A., Evans, H., Evans, S., Field, T., Fielding, H., Fisher, A., Flavell, W.R., Ford, R., Frasinski, L.J., Freeman, N., Galayda, J.N., Gardner, P., Garside, J., Gay, N.J., Gejo, T., George, M., Gray, M.D., Greenshaw, T.J., Greig, D., Halsall, M.P., Hamilton, B., Harrison, N.M., Hasnain, S.S., Hatherly, P.A., Heathcote, P., Helliwell, J.R., Henderson, C.M.B, Hepburn, J., Hill, J., Hirst, G., Hirst, J.D., Holland, D.M.P., Horn, A.B., Horton, P., Hunt, M.R.C., Hutchinson, H., Inglesfield, J.E., Ivanov, V.K., Johnson, C.A.F., Johnson, L.N., Jones, D., Jones, F.H., Jones, G.R., Jones, L., Kadodwala, M., Karlsson, L., Kennedy, E.T., King, G.C., King, M.R.F., Kirkman, I.W., Kleese, K., Knight, P.L., Kylstra, N., Larkins, F.P., Latimer, C., Lawley, K.P., Leggett, G.J., Lewis, R.A., Lindsey, K., Lu, J.R., Lyng, F.M., Macdonald, M.A., Malins, A., Marangos, J.P., Margaritondo, G., Marsi, M., Marston, G., Martin, S.R., Martin-Fernandez, M.L., Mason, N.J., Matthew, J.A.D., McCoustra, M.R.S., McGilp, J., McGovern, I.T., McGrath, R., Meldrum, R.A., Meyer, M., Millar, T.J., Mitchell, D., Møller, S.P., Molster, F.J., Moriarty, P., Morin, P., Munro, I.H., Murdin, B.N., Nahon, L., Newell, W.R., Noble, C.J., Nordgren, E.J., Norman, P.R., O'Brien, P., O'Neill, P., O'Shea, P., Owen, H., Pain, R., Papiz, M., Parker, A., Parker, J., Parr, A., Pattrick, R., Pemble, M.E., Picardo, M., Pidgeon, C.R., Pinheiro, T.J.T., Poliakoff, E.D., Poole, M.W., Potts, A., Potvliege, R., Powis, I., Price, S.D., Quinn, F.M., Radford, S., Rachlew-Källne, E., Raval, R., Read, F.H., Reddish, T.J., Ridley, P.A., Roberts, G., Russell, A.E., Ryan, A.J., Sapelkin, A., Sato, S., Schneider, A., Seddon, E.A., Shaw, E.A., Shen, T., Sherwood, P., Šiller, L., Smith, A.D., Smith, D.A., Smith, I., Smith, S.L., Snowdon, K., Softley, T.P., Sokell, E., Southworth, S.H., Srivistava, G.P., Stankiewicz, M., Sule-Suso, J., Sutherland, J.C., Surman, M., Svensson, S., Taylor, A.O., Temmerman, W.M., Thomas, A., Tiddy, G.J., Tobin, M., Towns-Andrews, Elizabeth, Towrie, M., Truscott, G., Tuckett, R.P., Turner, Tracy, Twigg, M.V., Vagdama, P., van der Hart, H.W., Volk, M., Vrakkring, M.J.J., Walker, I.C., Wander, A., Wasserman, S.P., Watanabe, M., Weightman, P., Welton, T., West, J.B., Wharton, C.W., Whitehead, J.C., Williams, G.P., Winick, H., Withnall, R., Woodruff, D.P., and Zayats, A.

Subjects
Q1
Published
2001

36. Quantum cascade laser absorption spectroscopy as a plasma diagnostic tool: an overview

Author

Welzel, S., Hempel, F., Hübner, M., Lang, N., Davies, P.B., Röpcke, J., Welzel, S., Hempel, F., Hübner, M., Lang, N., Davies, P.B., and Röpcke, J.

Abstract

The recent availability of thermoelectrically cooled pulsed and continuous wave quantum and inter-band cascade lasers in the mid-infrared spectral region has led to significant improvements and new developments in chemical sensing techniques using in-situ laser absorption spectroscopy for plasma diagnostic purposes. The aim of this article is therefore two-fold: (i) to summarize the challenges which arise in the application of quantum cascade lasers in such environments, and, (ii) to provide an overview of recent spectroscopic results (encompassing cavity enhanced methods) obtained in different kinds of plasma used in both research and industry.

Published
2010

37. Kinetic and diagnostic studies of molecular plasmas using laser absorption techniques

Author

Welzel, S., Rousseau, A., Davies, P.B., Röpcke, J., Welzel, S., Rousseau, A., Davies, P.B., and Röpcke, J.

Abstract

Within the last decade mid infrared absorption spectroscopy between 3 and 20 µm, known as Infrared Laser Absorption Spectroscopy (IRLAS) and based on tuneable semiconductor lasers, namely lead salt diode lasers, often called tuneable diode lasers (TDL), and quantum cascade lasers (QCL) has progressed considerably as a powerful diagnostic technique for in situ studies of the fundamental physics and chemistry of molecular plasmas. The increasing interest in processing plasmas containing hydrocarbons, fluorocarbons, organo-silicon and boron compounds has lead to further applications of IRLAS because most of these compounds and their decomposition products are infrared active. IRLAS provides a means of determining the absolute concentrations of the ground states of stable and transient molecular species, which is of particular importance for the investigation of reaction kinetics. Information about gas temperature and population densities can also be derived from IRLAS measurements. A variety of free radicals and molecular ions have been detected, especially using TDLs. Since plasmas with molecular feed gases are used in many applications such as thin film deposition, semiconductor processing, surface activation and cleaning, and materials and waste treatment, this has stimulated the adaptation of infrared spectroscopic techniques to industrial requirements. The recent development of QCLs offers an attractive new option for the monitoring and control of industrial plasma processes as well as for highly time-resolved studies on the kinetics of plasma processes. The aim of the present article is threefold: (i) to review recent achievements in our understanding of molecular phenomena in plasmas, (ii) to report on selected studies of the spectroscopic properties and kinetic behaviour of radicals, and (iii) to describe the current status of advanced instrumentation for TDLAS in the mid infrared.

Published
2007

40. Using quantum cascade lasers with resonant optical cavities as a diagnostic tool

Author

Welzel, S., Lombardi, G., Davies, P.B., Engeln, R.A.H., Schram, D.C., Röpcke, J., Hempel, F., Plasma & Materials Processing, and Plasma-based gas conversion

Subjects
History, Absorption spectroscopy, business.industry, Chemistry, Infrared, Radiation, Laser, Computer Science Applications, Education, law.invention, Resonator, Optics, Semiconductor, Cascade, law, Optoelectronics, business, Spectroscopy
Abstract

Absorption spectroscopy based on optical resonators is known to be a very sensitive diagnostic technique. For many years the infrared spectral range could not be employed, because of the lack of suitable radiation sources with the required power and tunability. Recent advances in semiconductor laser technology, in particular the advent of quantum cascade lasers (QCL) provides new possibilities for highly sensitive and selective detection of molecular species. Cavity Enhanced Absorption Spectroscopy (CEAS) with a thermoelectrically (TE) cooled cw QCL emitting at 7.66 µm and employing a ~0.5 m long cavity yielded effective path lengths of 1080 m and a sensitivity of 2 x 10-7 cm-1 Hz-1/2, mainly limited by incomplete averaging over cavity resonances. The molecular concentration detection limit with a 20 s integration time was found to be 6 x 108 molecules/cm3 for N2O and 2 x 10 9 molecules/cm3 for CH4 which is good enough for the selective measurement of trace atmospheric constituents at 2.2 mbar. © 2009 IOP Publishing Ltd

Published
2009

41. Diagnostics of molecular plasmas and trace gas analysis using mid infrared lasers

Author

Röpcke, J., Davies, P.B., Glitsch, S., Hempel, F., Lang, N., Nägele, M., Rousseau, A., Wege, S., Welzel, S., Razeghi, M., Sudharsanan, R., Brown, G.J., and Plasma & Materials Processing

Subjects
Absorption spectroscopy, Chemistry, business.industry, Infrared, Far-infrared laser, Infrared spectroscopy, Laser, law.invention, Semiconductor laser theory, Optics, law, Optoelectronics, business, Quantum cascade laser, Spectroscopy
Abstract

Mid infrared (MIR) absorption spectroscopy between 3 and 20 μm, known as Infrared Laser Absorption Spectroscopy (IRLAS) and based on tuneable semiconductor lasers, namely lead salt diode lasers, often called tuneable diode lasers (TDL), and quantum cascade lasers (QCL) has progressed considerably as a powerful diagnostic technique for in situ studies of the fundamental physics and chemistry of molecular plasmas and for trace gas analysis. The increasing interest in molecular processing plasmas has lead to further applications of IRLAS. IRLAS provides a means of determining the absolute concentrations and temperatures of the ground states of stable and transient molecular species, which is of particular importance for the investigation of reaction kinetics. Since plasmas with molecular feed gases are used in many applications such as thin film deposition and semiconductor processing this has stimulated the adaptation of infrared spectroscopic techniques to industrial requirements. The recent development of QCLs offers an attractive new option for the monitoring and control of industrial plasma processes as well as for highly time-resolved studies on the kinetics of plasma processes and for trace gas analysis. The aim of the present contribution is threefold: (i) to report on selected studies of the spectroscopic properties and kinetic behaviour of the methyl radical, (ii) to review recent achievements in our understanding of molecular phenomena in plasmas and the influence of surfaces, and (iii) to describe the current status of advanced instrumentation for quantum cascade laser absorption spectroscopy (QCLAS).

Published
2009

49. A diode laser and modeling study of mixed (CH(sub 4)-H(sub 2)-O(sub 2)) AC plasmas

Author

Fan, W.Y., Knewstubb, P.F., Kaning, M., Mechold, L., Ropcke, J., and Davies, P.B.

Subjects
Laser plasmas -- Research, Chemical vapor deposition -- Research, Molecular structure -- Research, Diodes, Laser -- Research, Methyl groups -- Research, Molecules -- Research, Chemicals, plastics and rubber industries
Abstract

The concentrations of the methyl radical and stable complexes in an ac methane/hydrogen/oxygen (CH(sub 4)-H(sub 2)-O(sub 2)) plasma are calculated using infrared diode laser spectroscopy. All of the stable C-2 hydrocarbons and oxygen-bearing species including formaldehyde, methanol, formic acid, carbon dioxide and carbon monoxide are among the stable products detected. Good agreement between the model and observed concentrations of the detected species is also found.

Published
1999

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