Sensitive Mass Spectrometer for Time-Resolved Gas-Phase Chemistry Studies at High Pressures

doi:10.1021/acs.jpca.9b08393

This content will become publicly available on November 11, 2020

Title: Sensitive Mass Spectrometer for Time-Resolved Gas-Phase Chemistry Studies at High Pressures

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Abstract

Here, we report the construction of a new experimental apparatus for direct time-resolved probing of high-pressure gas-phase chemical reactions by photoionization mass spectrometry. The apparatus uses a laser photolysis slow-flow reactor, capable of operating at P = 0.3 — 100 bar and T = 300 — 1000 K. In this report, we initiate reactions in homogeneous gas mixtures by the photolysis of appropriate radical precursor using laser pulses at repetition rates of 1 — 10 Hz. The reacting mixture is continuously sampled into a vacuum chamber, ionized by VUV photons from laboratory-based discharge lamps or from a synchrotron beamline, and analyzed by a custom-designed mass spectrometer. Soft near-threshold ionization by tunable synchrotron radiation enables spectroscopic quantification of many key intermediates and products of chemical reactions. A novel ionization scheme in the high-density region of the sample gas jet increases the experimental sensitivity 100-fold, compared with existing instruments, without compromising mass resolution. A 40-kHz pulsed reflectron time-of-flight mass spectrometer in the orthogonal acceleration geometry achieves simultaneous detection of all ionized species with 25-μs time resolution. We show the power of this apparatus by investigating the ethyl radical oxidation reaction using very dilute (<10 ¹² molecules • cm ^-3) ethyl concentrations atmore » pressures up to 25 bar.« less

Authors:

^[1]; Antonov, Ivan ^[1]; Au, Kendrew ^[1]

Sandia National Lab. (SNL-CA), Livermore, CA (United States)

Publication Date:: 2019-11-11

Research Org.:: Sandia National Lab. (SNL-CA), Livermore, CA (United States)

Sponsoring Org.:: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division

OSTI Identifier:: 1574695

Report Number(s):: SAND-2019-10135J
Journal ID: ISSN 1089-5639; 678901

Grant/Contract Number:: AC04-94AL85000; NA0003525; AC02-05CH11231

Resource Type:: Accepted Manuscript

Journal Name:: Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory

Additional Journal Information:: Journal Volume: 123; Journal Issue: 50; Journal ID: ISSN 1089-5639

Publisher:: American Chemical Society

Country of Publication:: United States

Language:: English

Subject:: 47 OTHER INSTRUMENTATION

Citation Formats


                    Sheps, Leonid, Antonov, Ivan, and Au, Kendrew. Sensitive Mass Spectrometer for Time-Resolved Gas-Phase Chemistry Studies at High Pressures.  United States: N. p., 2019. 
        Web.  doi:10.1021/acs.jpca.9b08393.

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                    Sheps, Leonid, Antonov, Ivan, & Au, Kendrew. Sensitive Mass Spectrometer for Time-Resolved Gas-Phase Chemistry Studies at High Pressures.  United States.  doi:10.1021/acs.jpca.9b08393.

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                    Sheps, Leonid, Antonov, Ivan, and Au, Kendrew. Mon .  
        "Sensitive Mass Spectrometer for Time-Resolved Gas-Phase Chemistry Studies at High Pressures".  United States.  doi:10.1021/acs.jpca.9b08393.

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@article{osti_1574695,

  title        = {Sensitive Mass Spectrometer for Time-Resolved Gas-Phase Chemistry Studies at High Pressures},

  author       = {Sheps, Leonid and Antonov, Ivan and Au, Kendrew},

  abstractNote = {Here, we report the construction of a new experimental apparatus for direct time-resolved probing of high-pressure gas-phase chemical reactions by photoionization mass spectrometry. The apparatus uses a laser photolysis slow-flow reactor, capable of operating at P = 0.3 — 100 bar and T = 300 — 1000 K. In this report, we initiate reactions in homogeneous gas mixtures by the photolysis of appropriate radical precursor using laser pulses at repetition rates of 1 — 10 Hz. The reacting mixture is continuously sampled into a vacuum chamber, ionized by VUV photons from laboratory-based discharge lamps or from a synchrotron beamline, and analyzed by a custom-designed mass spectrometer. Soft near-threshold ionization by tunable synchrotron radiation enables spectroscopic quantification of many key intermediates and products of chemical reactions. A novel ionization scheme in the high-density region of the sample gas jet increases the experimental sensitivity 100-fold, compared with existing instruments, without compromising mass resolution. A 40-kHz pulsed reflectron time-of-flight mass spectrometer in the orthogonal acceleration geometry achieves simultaneous detection of all ionized species with 25-μs time resolution. We show the power of this apparatus by investigating the ethyl radical oxidation reaction using very dilute (<1012 molecules • cm-3) ethyl concentrations at pressures up to 25 bar.},

  doi          = {10.1021/acs.jpca.9b08393},

  journal      = {Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory},

  number       = 50,

  volume       = 123,

  place        = {United States},

  year         = {2019},

  month        = {11}

}

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