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

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:
ORCiD logo [1];  [1];  [1]
  1. Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Publication Date:
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.
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.
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.
@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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This content will become publicly available on November 11, 2020
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