A High Pressure Modulated Molecular Beam Mass Spectrometric Sampling System PDF Download

Author: C. A. Stearns
Publisher:
ISBN:
Category :
Languages : en
Pages : 62

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Author: Michael N. Soltys
Publisher:
ISBN:
Category : Biomass chemicals
Languages : en
Pages : 0

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Book Description
The theory of high pressure, molecular-beam mass spectrometric sampling is briefly reviewed, with a discussion of the principal phenomena that affect results. The hardware and circuits of the sampling and data acquisition system are described. Finally, system performance and capability are reviewed. Representative data outputs are included.

Author: Michael N. Soltys
Publisher:
ISBN:
Category : Biomass chemicals
Languages : en
Pages : 32

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Book Description
The theory of high pressure, molecular-beam mass spectrometric sampling is briefly reviewed, with a discussion of the principal phenomena that affect results. The hardware and circuits of the sampling and data acquisition system are described. Finally, system performance and capability are reviewed. Representative data outputs are included.

Author: John Chang
Publisher:
ISBN:
Category : Mass spectrometry
Languages : en
Pages : 65

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Author: John Hu-sen Chang
Publisher:
ISBN:
Category : Gas dynamics
Languages : en
Pages : 74

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In this paper experiments are preported on beam intensity and mass separation effects for a mass spectrometer sampling system designed for chemically reacting gases at 1,000K and one atmosphere. The coupling between the reacting chamber and the mass spectrometer was achieved by a supersonic molecular beam of the type suggested by Kantrowitz and Grey. The initial expansion was accomplished by a free jet from a continuum sonic orifice. The system was designed to minimize the change in chemical composition of the sampled gas by orifice boundary layer contamination, sample-skimmer interaction, chemical reactions and condensation during the expansion, mass separation and background gas infiltration. Beams from known sources were generated and sampled. The observed beam intensity and composition were compared to those calculated from theory. This paper also provides a compact statement of the present state of the art of molecular beam technology as it applies to sampling, together with enough background material to illustrate the main requirements imposed on molecular beam systems in this application. (Author).

Author: Frank T. Greene
Publisher:
ISBN:
Category :
Languages : en
Pages : 20

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Book Description
A technique has been developed for the mass spectrometric sampling of high temperature systems at atmospheric pressure and above. The gases to be sampled are expanded as a free jet, which is collimated into a molecular beam and introduced into the ion source of a mass spectrometer. Corrections must be made for two phenomena, mass separation and nucleation, which may accompany this sampling process. It has been possible to quantitatively sample stable products and free radicals from atmospheric and low pressure flames using a water-cooled probe. Condensible species have also been sampled using a probe in thermal equilibrium with the gas. It has not, however, been possible to sample with a cold probe species which form refractory condensed phases. These negative results with condensible species are attributed to interactions of the probe with the gas prior to the expansion. (Author).

Author: Carl Vernon Wikstrom
Publisher:
ISBN:
Category :
Languages : en
Pages : 252

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Author: Richard A. Beyer
Publisher:
ISBN:
Category :
Languages : en
Pages : 24

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The data acquisition capability of the time-of-flight mass spectrometer used with the molecular beam sampling system has been expanded. An oscilloscope intensity-modulated raster technique using negative film scanned by a microdensitometer provides simultaneous semi-quantitative time-resolved mass spectra of all masses up to 160 amu with time resolution down to 10 ms. A system of parallel sample/hold channels which follow predetermined masses with time resolution near that of the spectrometer cycle time has been assembled and shown to have good dynamic range, adequate mass resolution, and provide good reproducibility. This system has been used to study the products of low pressure pyrolysis of nitrocellulose and cyclotetramethylene tetranitramine/polyurethane binder. Using a carbon dioxide laser for heating the samples up to 5000 deg/s heating rate effects are clearly demonstrated for NC but are not observed for HMX/PU. Relative amounts of the major decomposition species observed for the HMX/PU were nitrous oxide, 100; nitrogen dioxide, 54; hydrogen cyanide, 42; formaldehyde, 39; and nitric oxide, 27. The large amounts of nitrogen dioxide is compatible with the breaking of the N-N bond as the first step of the thermal decomposition of HMX. (Author).

Author: Frances L. Sachs
Publisher:
ISBN:
Category : Mass spectrometers
Languages : en
Pages : 410

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Author: Paul W. Dimiduk
Publisher:
ISBN:
Category :
Languages : en
Pages : 14

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Book Description
The general concept of a probe system is described that will allow the mass spectrometric analysis of the pressure environments near 1 atmosphere and above which are of current practical interest. Applications include the detection of both the stable and highly unstable gas molecules present in reacting mixtures and determining the vapor species existing over reacting solids in any temperature range. Illustrative examples are given to show some of the kinds of important materials problems whose solutions may be speeded by application of this device. The current development status and the major remaining problems associated with this device are summarized. (Author).