How does the molecular velocity distribution affect kinetics measurements by time‐resolved mass spectrometry?

Taatjes, Craig A.

doi:10.1002/kin.20262

Cited by 27 publications

(25 citation statements)

References 23 publications

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“…Taatjes, 26 building on earlier work of Moore and Carr, 27 has examined the effect of the molecular velocity distribution on the determination of rate coefficients in time-resolved mass spectrometry.…”

Section: Temporal Instrument Response Functionmentioning

confidence: 99%

“…In effusive sampling, the full width spread in arrival time ∆t d is on the same order as t d , and Taatjes 26 and Carr 27 give a rule of thumb that systematic errors in measuring a first-order rate coefficient k will be essentially negligible if k∆t d < 0.1. For mass 58 (e.g., acetone) this rule suggests that reaction conditions should be adjusted so that k < 1300 s -1 .…”

Section: Temporal Instrument Response Functionmentioning

confidence: 99%

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The multiplexed chemical kinetic photoionization mass spectrometer: A new approach to isomer-resolved chemical kinetics

Osborn

Zou

Johnsen

et al. 2008

Review of Scientific Instruments

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Electronic mail: dlosbor@sandia.gov (DLO), cataatj@sandia.gov (CAT).We have developed a multiplexed time-and photon-energy-resolved photoionization mass spectrometer for the study of the kinetics and isomeric product branching of gas phase, neutral chemical reactions. The instrument utilizes a side-sampled flow tube reactor, continuously tunable synchrotron radiation for photoionization, a multi-mass double-focusing mass spectrometer with 100% duty cycle, and a time-and positionsensitive detector for single ion counting. This approach enables multiplexed, universal detection of molecules with high sensitivity and selectivity. In addition to measurement of rate coefficients as a function of temperature and pressure, different structural isomers can be distinguished based on their photoionization efficiency curves, providing a more detailed probe of reaction mechanisms. The multiplexed 3-dimensional data structure

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Section: Temporal Instrument Response Functionmentioning

confidence: 99%

Section: Temporal Instrument Response Functionmentioning

confidence: 99%

The multiplexed chemical kinetic photoionization mass spectrometer: A new approach to isomer-resolved chemical kinetics

Osborn

Zou

Johnsen

et al. 2008

Review of Scientific Instruments

Self Cite

199

175

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“…Also, the velocity spread in the bulk gas flow is smaller. Taatjes 24 calculated the predicted response of sampling 13 cm from the skimmer opening used by Lee and coworkers. Based on the velocity in a supersonic expansion compared to an effusive beam, Taatjes concluded that the fidelity of the supersonic beam sampling is sufficient to probe fairly rapid decay transients, acknowledging the fact that calculating the detailed characteristics of a supersonic expansion is complex.…”

Section: Validity Of Kinetics Measurementsmentioning

confidence: 99%

“…We have reconsidered both the sampling geometry of the pulsed Laval expansion and its impact on the validity of kinetic measurements using mass spectrometry techniques. 24 Details are presented for how this important sampling geometry aspect of the new instrument is addressed by the design of a novel symmetric airfoil-shaped sampling arrangement.…”

Section: Introductionmentioning

confidence: 99%

Airfoil sampling of a pulsed Laval beam with tunable vacuum ultraviolet synchrotron ionization quadrupole mass spectrometry: Application to low-temperature kinetics and product detection

Soorkia

Liu

Savee

et al. 2011

Review of Scientific Instruments

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A new pulsed Laval nozzle apparatus with vacuum ultraviolet (VUV) synchrotron photoionization quadrupole mass spectrometry is constructed to study low-temperature radicalneutral chemical reactions of importance for modeling the atmosphere of Titan and the outer planets. A design for the sampling geometry of a pulsed Laval nozzle expansion has been developed that operates successfully for the determination of rate coefficients by time-resolved mass spectrometry. The new concept employs airfoil sampling of the collimated expansion with excellent sampling throughput. Time-resolved profiles of the high Mach number gas flow obtained by photoionization signals show that perturbation of the collimated expansion by the airfoil is negligible. The reaction of C 2 H with C 2 H 2 is studied at 70 K as a proof-of-principle result for both low-temperature rate coefficient measurements and product identification based on the photoionization spectrum of the reaction product versus VUV photon energy. This approach can be used to provide new insights into reaction mechanisms occurring at kinetic rates close to the collision-determined limit.3

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“…In practice the response will fall somewhere between these limits; the density in the ionization region will be increased for the same mass flow rate because of the more peaked angular distribution of the supersonic expansion [18]. The improved time fidelity of supersonic sampling [19] may also permit higher densities of target molecules to be used. For example, at 10 bar pressure and 75 m orifice diameter the speed ratio (the ratio of the beam velocity to the average transverse speed) in the ejected beam should be approximately 20.…”

Section: High-pressure Mbms Reactormentioning

confidence: 99%

Advanced fuel chemistry for advanced engines.

Taatjes¹,

Jusinski²,

Zádor³

et al. 2009

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Autoignition chemistry is central to predictive modeling of many advanced engine designs that combine high efficiency and low inherent pollutant emissions. This chemistry, and especially its pressure dependence, is poorly known for fuels derived from heavy petroleum and for biofuels, both of which are becoming increasingly prominent in the nation's fuel stream. We have investigated the pressure dependence of key ignition reactions for a series of molecules representative of non-traditional and alternative fuels. These investigations combined experimental characterization of hydroxyl radical production in well-controlled photolytically initiated oxidation and a hybrid modeling strategy that linked detailed quantum chemistry and computational kinetics of critical reactions with rate-equation models of the global chemical system. Comprehensive mechanisms for autoignition generally ignore the pressure dependence of branching fractions in the important alkyl + O 2 reaction systems; however we have demonstrated that pressure-dependent "formally direct" pathways persist at in-cylinder pressures. 4 ACKNOWLEDGMENTSWe thank Dr. Ahren Jasper (8353) for assistance in quantum chemistry and fundamental computational kinetic methods; Dr. David Osborn (8353) and Dr. John T. Farrell (ExxonMobil) for assistance in the design of the high-pressure MBMS reactor. We also thank Prof. Giovanni Meloni (University of San Francisco) for his contributions to the experimental investigations.5

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How does the molecular velocity distribution affect kinetics measurements by time‐resolved mass spectrometry?

Cited by 27 publications

References 23 publications

The multiplexed chemical kinetic photoionization mass spectrometer: A new approach to isomer-resolved chemical kinetics

The multiplexed chemical kinetic photoionization mass spectrometer: A new approach to isomer-resolved chemical kinetics

Airfoil sampling of a pulsed Laval beam with tunable vacuum ultraviolet synchrotron ionization quadrupole mass spectrometry: Application to low-temperature kinetics and product detection

Advanced fuel chemistry for advanced engines.

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